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Tan H, Liu Y, Guo H. The biogenesis, regulation and functions of transitive siRNA in plants. Acta Biochim Biophys Sin (Shanghai) 2024. [PMID: 39376148 DOI: 10.3724/abbs.2024160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/09/2024] Open
Abstract
Small RNA (sRNA)-mediated RNA interference (RNAi) is a sequence-specific gene silencing mechanism that modulates gene expression in eukaryotes. As core molecules of RNAi, various sRNAs are encoded in the plant genome or derived from invading RNA molecules, and their biogenesis depends on distinct genetic pathways. Transitive small interfering RNAs (siRNAs), which are sRNAs produced from double-strand RNA (dsRNA) in a process that depends on RNA-dependent RNA polymerases (RDRs), can amplify and spread silencing signals to additional transcripts, thereby enabling a phenomenon termed "transitive RNAi". Members of this class of siRNAs function in various biological processes ranging from development to stress adaptation. In Arabidopsis thaliana, two RDRs participate in the generation of transitive siRNAs, acting cooperatively with various siRNA generation-related factors, such as the RNA-induced silencing complex (RISC) and aberrant RNAs. Transitive siRNAs are produced in diverse subcellular locations and structures under the control of various mechanisms, highlighting the intricacies of their biogenesis and functions. In this review, we discuss recent advances in understanding the molecular events of transitive siRNA biogenesis and its regulation, with a particular focus on factors involved in RDR recruitment. We aim to provide a comprehensive description of the generalized mechanism governing the biogenesis of transitive siRNAs. Additionally, we present an overview of the diverse biological functions of these siRNAs and raise some pressing questions in this area for further investigation.
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Affiliation(s)
- Huijun Tan
- Shenzhen Key Laboratory of Plant Genetic Engineering and Molecular Design, Institute of Plant and Food Science, Department of Biology, School of Life Sciences, Southern University of Science and Technology, Shenzhen 518055, China
- Department of Biology, Hong Kong Baptist University, Hong Kong SAR, China
| | - Yuelin Liu
- Shenzhen Key Laboratory of Plant Genetic Engineering and Molecular Design, Institute of Plant and Food Science, Department of Biology, School of Life Sciences, Southern University of Science and Technology, Shenzhen 518055, China
| | - Hongwei Guo
- Shenzhen Key Laboratory of Plant Genetic Engineering and Molecular Design, Institute of Plant and Food Science, Department of Biology, School of Life Sciences, Southern University of Science and Technology, Shenzhen 518055, China
- Shenzhen Branch, Guangdong Laboratory for Lingnan Modern Agriculture, Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen 518120, China
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2
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Fujimoto Y, Iwakawa HO. Mechanisms that regulate the production of secondary siRNAs in plants. J Biochem 2023; 174:491-499. [PMID: 37757447 DOI: 10.1093/jb/mvad071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 08/28/2023] [Accepted: 09/21/2023] [Indexed: 09/29/2023] Open
Abstract
Many organisms produce secondary small interfering RNAs (siRNAs) that are triggered by primary small RNAs to regulate various biological processes. Plants have evolved several types of secondary siRNA biogenesis pathways that play important roles in development, stress responses and defense against viruses and transposons. The critical step of these pathways is the production of double-stranded RNAs by RNA-dependent RNA polymerases. This step is normally tightly regulated, but when its control is released, secondary siRNA production is initiated. In this article, we will review the recent advances in secondary siRNA production triggered by microRNAs encoded in the genome and siRNAs derived from invasive nucleic acids. In particular, we will focus on the factors, events, and RNA/DNA elements that promote or inhibit the early steps of secondary siRNA biogenesis.
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Affiliation(s)
- Yuji Fujimoto
- Department of Life Science, College of Science, Rikkyo University, Toshima-ku, Tokyo 171-8501, Japan
| | - Hiro-Oki Iwakawa
- Department of Life Science, College of Science, Rikkyo University, Toshima-ku, Tokyo 171-8501, Japan
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3
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López-Márquez D, Del-Espino Á, Ruiz-Albert J, Bejarano ER, Brodersen P, Beuzón CR. Regulation of plant immunity via small RNA-mediated control of NLR expression. JOURNAL OF EXPERIMENTAL BOTANY 2023; 74:6052-6068. [PMID: 37449766 PMCID: PMC10575705 DOI: 10.1093/jxb/erad268] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Accepted: 07/13/2023] [Indexed: 07/18/2023]
Abstract
Plants use different receptors to detect potential pathogens: membrane-anchored pattern recognition receptors (PRRs) activated upon perception of pathogen-associated molecular patterns (PAMPs) that elicit pattern-triggered immunity (PTI); and intracellular nucleotide-binding leucine-rich repeat proteins (NLRs) activated by detection of pathogen-derived effectors, activating effector-triggered immunity (ETI). The interconnections between PTI and ETI responses have been increasingly reported. Elevated NLR levels may cause autoimmunity, with symptoms ranging from fitness cost to developmental arrest, sometimes combined with run-away cell death, making accurate control of NLR dosage key for plant survival. Small RNA-mediated gene regulation has emerged as a major mechanism of control of NLR dosage. Twenty-two nucleotide miRNAs with the unique ability to trigger secondary siRNA production from target transcripts are particularly prevalent in NLR regulation. They enhance repression of the primary NLR target, but also bring about repression of NLRs only complementary to secondary siRNAs. We summarize current knowledge on miRNAs and siRNAs in the regulation of NLR expression with an emphasis on 22 nt miRNAs and propose that miRNA and siRNA regulation of NLR levels provides additional links between PTI and NLR defense pathways to increase plant responsiveness against a broad spectrum of pathogens and control an efficient deployment of defenses.
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Affiliation(s)
- Diego López-Márquez
- Department of Biology, University of Copenhagen, Copenhagen N, DK-2200, Denmark
| | - Ángel Del-Espino
- Instituto de Hortofruticultura Subtropical y Mediterránea ‘La Mayora’, Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Depto. Biología Celular, Genética y Fisiología, Málaga, Spain
| | - Javier Ruiz-Albert
- Instituto de Hortofruticultura Subtropical y Mediterránea ‘La Mayora’, Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Depto. Biología Celular, Genética y Fisiología, Málaga, Spain
| | - Eduardo R Bejarano
- Instituto de Hortofruticultura Subtropical y Mediterránea ‘La Mayora’, Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Depto. Biología Celular, Genética y Fisiología, Málaga, Spain
| | - Peter Brodersen
- Department of Biology, University of Copenhagen, Copenhagen N, DK-2200, Denmark
| | - Carmen R Beuzón
- Instituto de Hortofruticultura Subtropical y Mediterránea ‘La Mayora’, Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Depto. Biología Celular, Genética y Fisiología, Málaga, Spain
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4
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Hu W, Dai Z, Liu P, Deng C, Shen W, Li Z, Cui H. The Single Distinct Leader Protease Encoded by Alpinia oxyphylla Mosaic Virus (Genus Macluravirus) Suppresses RNA Silencing Through Interfering with Double-Stranded RNA Synthesis. PHYTOPATHOLOGY 2023; 113:1103-1114. [PMID: 36576401 DOI: 10.1094/phyto-10-22-0371-r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
The genomic 5'-terminal regions of viruses in the family Potyviridae (potyvirids) encode two types of leader proteases: serine-protease (P1) and cysteine-protease (HCPro), which differ greatly in the arrangement and sequence composition among inter-genus viruses. Most potyvirids have the same tandemly arranged P1 and HCPro, whereas viruses in the genus Macluravirus encode a single distinct leader protease, a truncated version of HCPro with yet-unknown functions. We investigated the RNA silencing suppression (RSS) activity and its underpinning mechanism of the distinct HCPro from alpinia oxyphylla mosaic macluravirus (aHCPro). Sequence analysis revealed that macluraviral HCPros have obvious truncations in the N-terminal and middle regions when aligned to their counterparts in potyviruses (well-characterized viral suppressors of RNA silencing). Nearly all defined elements essential for the RSS activity of potyviral counterparts are not distinguished in macluraviral HCPros. Here, we demonstrated that aHCPro exhibits a similar anti-silencing activity with the potyviral counterpart. However, aHCPro fails to block both the local and systemic spreading of RNA silencing. In line, aHCPro interferes with the dsRNA synthesis, an upstream step in the RNA silencing pathway. Affinity-purification and NanoLC-MS/MS analysis revealed that aHCPro has no association with core components or their potential interactors involving in dsRNA synthesis from the protein layer. Instead, the ectopic expression of aHCPro significantly reduces the transcript abundance of RDR2, RDR6, SGS3, and SDE5. This study represents the first report on the anti-silencing function of Macluravirus-encoded HCPro and the underlying molecular mechanism.
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Affiliation(s)
- Weiyao Hu
- Sanya Nanfan Research Institute, Key Laboratory of Green Prevention and Control of Tropical Plant Diseases and Pests (Ministry of Education) and College of Plant Protection, Hainan University, Haikou, Hainan, 570228, China
| | - Zhaoji Dai
- Sanya Nanfan Research Institute, Key Laboratory of Green Prevention and Control of Tropical Plant Diseases and Pests (Ministry of Education) and College of Plant Protection, Hainan University, Haikou, Hainan, 570228, China
| | - Peilan Liu
- Sanya Nanfan Research Institute, Key Laboratory of Green Prevention and Control of Tropical Plant Diseases and Pests (Ministry of Education) and College of Plant Protection, Hainan University, Haikou, Hainan, 570228, China
| | - Changhui Deng
- Sanya Nanfan Research Institute, Key Laboratory of Green Prevention and Control of Tropical Plant Diseases and Pests (Ministry of Education) and College of Plant Protection, Hainan University, Haikou, Hainan, 570228, China
| | - Wentao Shen
- Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou, Hainan, 571101, China
| | - Zengping Li
- Sanya Nanfan Research Institute, Key Laboratory of Green Prevention and Control of Tropical Plant Diseases and Pests (Ministry of Education) and College of Plant Protection, Hainan University, Haikou, Hainan, 570228, China
| | - Hongguang Cui
- Sanya Nanfan Research Institute, Key Laboratory of Green Prevention and Control of Tropical Plant Diseases and Pests (Ministry of Education) and College of Plant Protection, Hainan University, Haikou, Hainan, 570228, China
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5
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Phase separation of SGS3 drives siRNA body formation and promotes endogenous gene silencing. Cell Rep 2023; 42:111985. [PMID: 36640363 DOI: 10.1016/j.celrep.2022.111985] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 10/26/2022] [Accepted: 12/23/2022] [Indexed: 01/11/2023] Open
Abstract
The generation of small interfering RNA (siRNA) involves many RNA processing components, including SUPPRESSOR OF GENE SILENCING 3 (SGS3), RNA-DEPENDENT RNA POLYMERASE 6 (RDR6), and DICER-LIKE proteins (DCLs). Nonetheless, how these components are coordinated to produce siRNAs is unclear. Here, we show that SGS3 forms condensates via phase separation in vivo and in vitro. SGS3 interacts with RDR6 and drives it to form siRNA bodies in cytoplasm, which is promoted by SGS3-targeted RNAs. Disrupting SGS3 phase separation abrogates siRNA body assembly and siRNA biogenesis, whereas coexpression of SGS3 and RDR6 induces siRNA body formation in tobacco and yeast cells. Dysfunction in translation and mRNA decay increases the number of siRNA bodies, whereas DCL2/4 mutations enhance their size. Purification of SGS3 condensates identifies numerous RNA-binding proteins and siRNA processing components. Together, our findings reveal that SGS3 phase separation-mediated formation of siRNA bodies is essential for siRNA production and gene silencing.
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Abstract
With the increasing understanding of fundamentals of gene silencing pathways in plants, various tools and techniques for downregulating the expression of a target gene have been developed across multiple plant species. This chapter provides an insight into the molecular mechanisms of gene silencing and highlights the advancements in various gene silencing approaches. The prominent aspects of different gene silencing methods, their advantages and disadvantages have been discussed. A succinct discussion on the newly emerged microRNA-based technologies like microRNA-induced gene silencing (MIGS) and microRNA-mediated virus-induced gene silencing (MIR-VIGS) are also presented. We have also discussed the gene-editing system like CRISPR-Cas. The prominent bottlenecks in gene silencing methods are the off-target effects and lack of universal applicability. However, the tremendous growth in understanding of this field reflects the potentials for improvements in the currently available approaches and the development of new widely applicable methods for easy, fast, and efficient functional characterization of plant genes.
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Affiliation(s)
- Prachi Pandey
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi, India
| | - Kirankumar S Mysore
- Institute for Agricultural Biosciences, Oklahoma State University, Ardmore, OK, USA
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7
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Cooperative recruitment of RDR6 by SGS3 and SDE5 during small interfering RNA amplification in Arabidopsis. Proc Natl Acad Sci U S A 2021; 118:2102885118. [PMID: 34408020 DOI: 10.1073/pnas.2102885118] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Small interfering RNAs (siRNAs) are often amplified from transcripts cleaved by RNA-induced silencing complexes (RISCs) containing a small RNA (sRNA) and an Argonaute protein. Amplified siRNAs, termed secondary siRNAs, are important for reinforcement of target repression. In plants, target cleavage by RISCs containing 22-nucleotide (nt) sRNA and Argonaute 1 (AGO1) triggers siRNA amplification. In this pathway, the cleavage fragment is converted into double-stranded RNA (dsRNA) by RNA-dependent RNA polymerase 6 (RDR6), and the dsRNA is processed into siRNAs by Dicer-like proteins. Because nonspecific RDR6 recruitment causes nontarget siRNA production, it is critical that RDR6 is specifically recruited to the target RNA that serves as a template for dsRNA formation. Previous studies showed that Suppressor of Gene Silencing 3 (SGS3) binds and stabilizes 22-nt sRNA-containing AGO1 RISCs associated with cleaved target, but how RDR6 is recruited to targets cleaved by 22-nt sRNA-containing AGO1 RISCs remains unknown. Here, using cell-free extracts prepared from suspension-cultured Arabidopsis thaliana cells, we established an in vitro system for secondary siRNA production in which 22-nt siRNA-containing AGO1-RISCs but not 21-nt siRNA-containing AGO1-RISCs induce secondary siRNA production. In this system, addition of recombinant Silencing Defective 5 (SDE5) protein remarkably enhances secondary siRNA production. We show that RDR6 is recruited to a cleavage fragment by 22-nt siRNA-containing AGO1-RISCs in coordination with SGS3 and SDE5. The SGS3-SDE5-RDR6 multicomponent recognition system and the poly(A) tail inhibition may contribute to securing specificity of siRNA amplification.
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8
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Sakurai Y, Baeg K, Lam AYW, Shoji K, Tomari Y, Iwakawa HO. Cell-free reconstitution reveals the molecular mechanisms for the initiation of secondary siRNA biogenesis in plants. Proc Natl Acad Sci U S A 2021; 118:e2102889118. [PMID: 34330830 PMCID: PMC8346886 DOI: 10.1073/pnas.2102889118] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Secondary small interfering RNA (siRNA) production, triggered by primary small RNA targeting, is critical for proper development and antiviral defense in many organisms. RNA-dependent RNA polymerase (RDR) is a key factor in this pathway. However, how RDR specifically converts the targets of primary small RNAs into double-stranded RNA (dsRNA) intermediates remains unclear. Here, we develop an in vitro system that allows for dissection of the molecular mechanisms underlying the production of trans-acting siRNAs, a class of plant secondary siRNAs that play roles in organ development and stress responses. We find that a combination of the dsRNA-binding protein, SUPPRESSOR OF GENE SILENCING3; the putative nuclear RNA export factor, SILENCING DEFECTIVE5, primary small RNA, and Argonaute is required for physical recruitment of RDR6 to target RNAs. dsRNA synthesis by RDR6 is greatly enhanced by the removal of the poly(A) tail, which can be achieved by the cleavage at a second small RNA-binding site bearing appropriate mismatches. Importantly, when the complementarity of the base pairing at the second target site is too strong, the small RNA-Argonaute complex remains at the cleavage site, thereby blocking the initiation of dsRNA synthesis by RDR6. Our data highlight the light and dark sides of double small RNA targeting in the secondary siRNA biogenesis.
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Affiliation(s)
- Yuriki Sakurai
- Institute for Quantitative Biosciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Kyungmin Baeg
- Institute for Quantitative Biosciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Andy Y W Lam
- Institute for Quantitative Biosciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Keisuke Shoji
- Institute for Quantitative Biosciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Yukihide Tomari
- Institute for Quantitative Biosciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan;
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Hiro-Oki Iwakawa
- Institute for Quantitative Biosciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan;
- Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST), Saitama 332-0012, Japan
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9
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The diversity of post-transcriptional gene silencing mediated by small silencing RNAs in plants. Essays Biochem 2021; 64:919-930. [PMID: 32885814 DOI: 10.1042/ebc20200006] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2020] [Revised: 08/11/2020] [Accepted: 08/14/2020] [Indexed: 12/31/2022]
Abstract
In plants, post-transcriptional gene silencing (PTGS) tightly regulates development, maintains genome stability and protects plant against foreign genes. PTGS can be triggered by virus infection, transgene, and endogenous transcript, thus commonly serves as an RNA-based immune mechanism. Accordingly, based on the initiating factors, PTGS can be divided into viral-PTGS, transgene-PTGS, and endo-gene-PTGS. Unlike the intensely expressed invading transgenes and viral genes that frequently undergo PTGS, most endogenous genes do not trigger PTGS, except for a few that can produce endogenous small RNAs (sRNAs), including microRNA (miRNA) and small interfering RNA (siRNA). Different lengths of miRNA and siRNA, mainly 21-, 22- or 24-nucleotides (nt) exert diverse functions, ranging from target mRNA degradation, translational inhibition, or DNA methylation and chromatin modifications. The abundant 21-nt miRNA or siRNA, processed by RNase-III enzyme DICER-LIKE 1 (DCL1) and DCL4, respectively, have been well studied in the PTGS pathways. By contrast, the scarceness of endogenous 22-nt sRNAs that are primarily processed by DCL2 limits their research, although a few encouraging studies have been reported recently. Therefore, we review here our current understanding of diverse PTGS pathways triggered by a variety of sRNAs and summarize the distinct features of the 22-nt sRNA mediated PTGS.
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Song L, Fang Y, Chen L, Wang J, Chen X. Role of non-coding RNAs in plant immunity. PLANT COMMUNICATIONS 2021; 2:100180. [PMID: 34027394 PMCID: PMC8132121 DOI: 10.1016/j.xplc.2021.100180] [Citation(s) in RCA: 56] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Revised: 03/01/2021] [Accepted: 03/17/2021] [Indexed: 05/06/2023]
Abstract
Crops are exposed to attacks by various pathogens that cause substantial yield losses and severely threaten food security. To cope with pathogenic infection, crops have elaborated strategies to enhance resistance against pathogens. In addition to the role of protein-coding genes as key regulators in plant immunity, accumulating evidence has demonstrated the importance of non-coding RNAs (ncRNAs) in the plant immune response. Here, we summarize the roles and molecular mechanisms of endogenous ncRNAs, especially microRNAs (miRNAs), long ncRNAs (lncRNAs), and circular RNAs (circRNAs), in plant immunity. We discuss the coordination between miRNAs and small interfering RNAs (siRNAs), between lncRNAs and miRNAs or siRNAs, and between circRNAs and miRNAs in the regulation of plant immune responses. We also address the role of cross-kingdom mobile small RNAs in plant-pathogen interactions. These insights improve our understanding of the mechanisms by which ncRNAs regulate plant immunity and can promote the development of better approaches for breeding disease-resistant crops.
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Affiliation(s)
- Li Song
- State Key Laboratory of Crop Gene Exploration and Utilization in Southwest China, Rice Research Institute, Sichuan Agricultural University at Wenjiang, Chengdu, Sichuan 611130, China
| | - Yu Fang
- State Key Laboratory of Crop Gene Exploration and Utilization in Southwest China, Rice Research Institute, Sichuan Agricultural University at Wenjiang, Chengdu, Sichuan 611130, China
| | - Lin Chen
- State Key Laboratory of Crop Gene Exploration and Utilization in Southwest China, Rice Research Institute, Sichuan Agricultural University at Wenjiang, Chengdu, Sichuan 611130, China
| | - Jing Wang
- State Key Laboratory of Crop Gene Exploration and Utilization in Southwest China, Rice Research Institute, Sichuan Agricultural University at Wenjiang, Chengdu, Sichuan 611130, China
- Corresponding author
| | - Xuewei Chen
- State Key Laboratory of Crop Gene Exploration and Utilization in Southwest China, Rice Research Institute, Sichuan Agricultural University at Wenjiang, Chengdu, Sichuan 611130, China
- Corresponding author
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11
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RNAi activation with homologous and heterologous sequences that induce resistance against the begomovirus Pepper golden mosaic virus (PepGMV). 3 Biotech 2021; 11:114. [PMID: 33604230 DOI: 10.1007/s13205-021-02653-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Accepted: 01/09/2021] [Indexed: 12/27/2022] Open
Abstract
This study compared the transcriptional changes in Nicotiana benthamiana plants treated with homologous sequences derived from Pepper golden mosaic virus (PepGMV) and heterologous sequences that derived from another begomovirus, Tomato chino La Paz virus (ToChLPV) prior to infection by PepGMV. The results of microarray analyses identified upregulated genes associated with RNAi such as DCL2, DCL4, AGO3, AGO7, AGO10, NRPD2B (Pol IV), DRB3, CMT3, RDR6. The components that participate in different RNAi pathways were identified, including methylation induced by both constructs, as well as the code of these genes in Arabidopsis thaliana and its counterpart in N. benthamiana through different genome assembly. The expression of these genes was validated by quantitative reverse transcription polymerase chain reaction (RT-qPCR), where DCL3, DCL4, AGO1-1, AGO2, RDR6 and PPR1 showed increased expression during plant protection with the heterologous construct compared to those protected with the homologous construct. The results of this study confirmed the activation of the gene silencing mechanism at the transcriptional level with both constructs and established the possibility of their use as a protection system for both homologous and heterologous sequences.
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12
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de Felippes FF. Gene Regulation Mediated by microRNA-Triggered Secondary Small RNAs in Plants. PLANTS (BASEL, SWITZERLAND) 2019; 8:E112. [PMID: 31035467 PMCID: PMC6572396 DOI: 10.3390/plants8050112] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/31/2019] [Revised: 04/22/2019] [Accepted: 04/24/2019] [Indexed: 01/18/2023]
Abstract
In plants, proper development and response to abiotic and biotic stimuli requires an orchestrated regulation of gene expression. Small RNAs (sRNAs) are key molecules involved in this process, leading to downregulation of their target genes. Two main classes of sRNAs exist, the small interfering RNAs (siRNAs) and microRNAs (miRNAs). The role of the latter class in plant development and physiology is well known, with many examples of how miRNAs directly impact the expression of genes in cells where they are produced, with dramatic consequences to the life of the plant. However, there is an aspect of miRNA biology that is still poorly understood. In some cases, miRNA targeting can lead to the production of secondary siRNAs from its target. These siRNAs, which display a characteristic phased production pattern, can act in cis, reinforcing the initial silencing signal set by the triggering miRNA, or in trans, affecting genes that are unrelated to the initial target. In this review, the mechanisms and implications of this process in the gene regulation mediated by miRNAs will be discussed. This work will also explore techniques for gene silencing in plants that are based on this unique pathway.
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13
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RNA Interference: A Natural Immune System of Plants to Counteract Biotic Stressors. Cells 2019; 8:cells8010038. [PMID: 30634662 PMCID: PMC6356646 DOI: 10.3390/cells8010038] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Revised: 01/01/2019] [Accepted: 01/07/2019] [Indexed: 02/06/2023] Open
Abstract
During plant-pathogen interactions, plants have to defend the living transposable elements from pathogens. In response to such elements, plants activate a variety of defense mechanisms to counteract the aggressiveness of biotic stressors. RNA interference (RNAi) is a key biological process in plants to inhibit gene expression both transcriptionally and post-transcriptionally, using three different groups of proteins to resist the virulence of pathogens. However, pathogens trigger an anti-silencing mechanism through the expression of suppressors to block host RNAi. The disruption of the silencing mechanism is a virulence strategy of pathogens to promote infection in the invaded hosts. In this review, we summarize the RNA silencing pathway, anti-silencing suppressors, and counter-defenses of plants to viral, fungal, and bacterial pathogens.
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Yang Z, Li Y. Dissection of RNAi-based antiviral immunity in plants. Curr Opin Virol 2018; 32:88-99. [PMID: 30388659 DOI: 10.1016/j.coviro.2018.08.003] [Citation(s) in RCA: 88] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Revised: 08/03/2018] [Accepted: 08/05/2018] [Indexed: 10/28/2022]
Abstract
RNA interference (RNAi)-based antiviral defense is a small RNA-dependent repression mechanism of plants to against viruses. Although the core components of antiviral RNAi are well known, it is unclear whether additional factors exist that regulate RNAi. Recently, a forward genetic screen identified two novel components of antiviral RNAi, providing important insights into the antiviral RNAi mechanism. Meanwhile, it was discovered that microRNAs make important contributions to host antiviral RNAi. On the other hand, to counteract host antiviral RNAi, most viruses encode viral suppressors of RNA silencing (VSRs). Recent studies have revealed the multiple functions of VSRs and the intricate interactions between plant hosts and viruses. These findings add to our knowledge of the sophisticated host antiviral defense mechanism in plants. Ongoing molecular functional studies will improve our understanding of the co-evolutionary arms race between viruses and plants, and thereby provide key information for the development of plant antiviral strategies.
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Affiliation(s)
- Zhirui Yang
- The State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing 100871, China
| | - Yi Li
- The State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing 100871, China.
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15
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SDE5, a putative RNA export protein, participates in plant innate immunity through a flagellin-dependent signaling pathway in Arabidopsis. Sci Rep 2017; 7:9859. [PMID: 28851870 PMCID: PMC5574965 DOI: 10.1038/s41598-017-07918-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Accepted: 06/15/2017] [Indexed: 12/02/2022] Open
Abstract
In eukaryotes, RNA silencing, mediated by small interfering RNAs, is an evolutionarily widespread and versatile silencing mechanism that plays an important role in various biological processes. Increasing evidences suggest that various components of RNA silencing pathway are involved in plant defense machinery against microbial pathogens in Arabidopsis thaliana. Here, we show genetic and molecular evidence that Arabidopsis SDE5 is required to generate an effective resistance against the biotrophic bacteria Pseudomonas syringae pv. tomato DC3000 and for susceptibility to the necrotrophic bacteria Erwinia caratovora pv. caratovora. SDE5, encodes a putative mRNA export factor that is indispensable for transgene silencing and the production of trans-acting siRNAs. SDE5 expression is rapidly induced by exogenous application of phytohormone salicylic acid (SA), methyl jasmonate (MeJA), phytopathogenic bacteria, and flagellin. We further report that SDE5 is involved in basal plant defense and mRNA export. Our genetic data suggests that SDE5 and Nonexpressor of PR Gene1 (NPR1) may contribute to the same SA-signaling pathway. However, SDE5 over-expressing transgenic plant exhibits reduced defense responsive phenotype after flagellin treatment. Taken together, these results support the conclusion that SDE5 contributes to plant innate immunity in Arabidopsis.
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Butel N, Le Masson I, Bouteiller N, Vaucheret H, Elmayan T. sgs1: a neomorphic nac52 allele impairing post-transcriptional gene silencing through SGS3 downregulation. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2017; 90:505-519. [PMID: 28207953 DOI: 10.1111/tpj.13508] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Accepted: 02/01/2017] [Indexed: 06/06/2023]
Abstract
Post-transcriptional gene silencing (PTGS) is a defense mechanism that targets invading nucleic acids from endogenous (transposons) or exogenous (pathogens, transgenes) sources. Genetic screens based on the reactivation of silenced transgenes have long been used to identify cellular components and regulators of PTGS. Here we show that the first isolated PTGS-deficient mutant, sgs1, is impaired in the transcription factor NAC52. This mutant exhibits striking similarities to a mutant impaired in the H3K4me3 demethylase JMJ14 isolated from the same genetic screen. These similarities include increased transgene promoter DNA methylation, reduced H3K4me3 and H3K36me3 levels, reduced PolII occupancy and reduced transgene mRNA accumulation. It is likely that increased DNA methylation is the cause of reduced transcription because the effect of jmj14 and sgs1 on transgene transcription is suppressed by drm2, a mutation that compromises de novo DNA methylation, suggesting that the JMJ14-NAC52 module promotes transgene transcription by preventing DNA methylation. Remarkably, sgs1 has a stronger effect than jmj14 and nac52 null alleles on PTGS systems requiring siRNA amplification, and this is due to reduced SGS3 mRNA levels in sgs1. Given that the sgs1 mutation changes a conserved amino acid of the NAC proteins involved in homodimerization, we propose that sgs1 corresponds to a neomorphic nac52 allele encoding a mutant protein that lacks wild-type NAC52 activity but promotes SGS3 downregulation. Together, these results indicate that impairment of PTGS in sgs1 is due to its dual effect on transgene transcription and SGS3 transcription, thus compromising siRNA amplification.
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Affiliation(s)
- Nicolas Butel
- Institut Jean-Pierre Bourgin, UMR 1318, INRA AgroParisTech CNRS, Université Paris-Saclay, 78000, Versailles, France
- Université Paris-Sud, Université Paris-Saclay, 91405, Orsay, France
| | - Ivan Le Masson
- Institut Jean-Pierre Bourgin, UMR 1318, INRA AgroParisTech CNRS, Université Paris-Saclay, 78000, Versailles, France
| | - Nathalie Bouteiller
- Institut Jean-Pierre Bourgin, UMR 1318, INRA AgroParisTech CNRS, Université Paris-Saclay, 78000, Versailles, France
| | - Hervé Vaucheret
- Institut Jean-Pierre Bourgin, UMR 1318, INRA AgroParisTech CNRS, Université Paris-Saclay, 78000, Versailles, France
| | - Taline Elmayan
- Institut Jean-Pierre Bourgin, UMR 1318, INRA AgroParisTech CNRS, Université Paris-Saclay, 78000, Versailles, France
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17
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Bejerman N, Mann KS, Dietzgen RG. Alfalfa dwarf cytorhabdovirus P protein is a local and systemic RNA silencing supressor which inhibits programmed RISC activity and prevents transitive amplification of RNA silencing. Virus Res 2016; 224:19-28. [PMID: 27543392 DOI: 10.1016/j.virusres.2016.08.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Revised: 08/09/2016] [Accepted: 08/14/2016] [Indexed: 11/16/2022]
Abstract
Plants employ RNA silencing as an innate defense mechanism against viruses. As a counter-defense, plant viruses have evolved to express RNA silencing suppressor proteins (RSS), which target one or more steps of the silencing pathway. In this study, we show that the phosphoprotein (P) encoded by the negative-sense RNA virus alfalfa dwarf virus (ADV), a species of the genus Cytorhabdovirus, family Rhabdoviridae, is a suppressor of RNA silencing. ADV P has a relatively weak local RSS activity, and does not prevent siRNA accumulation. On the other hand, ADV P strongly suppresses systemic RNA silencing, but does not interfere with the short-distance spread of silencing, which is consistent with its lack of inhibition of siRNA accumulation. The mechanism of suppression appears to involve ADV P binding to RNA-induced silencing complex proteins AGO1 and AGO4 as shown in protein-protein interaction assays when ectopically expressed. In planta, we demonstrate that ADV P likely functions by inhibiting miRNA-guided AGO1 cleavage and prevents transitive amplification by repressing the production of secondary siRNAs. As recently described for lettuce necrotic yellows cytorhabdovirus P, but in contrast to other viral RSS known to disrupt AGO activity, ADV P sequence does not contain any recognizable GW/WG or F-box motifs, which suggests that cytorhabdovirus P proteins may use alternative motifs to bind to AGO proteins.
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Affiliation(s)
- Nicolás Bejerman
- Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St. Lucia, QLD 4072, Australia.
| | - Krin S Mann
- Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St. Lucia, QLD 4072, Australia.
| | - Ralf G Dietzgen
- Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St. Lucia, QLD 4072, Australia.
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18
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Harris CJ, Husmann D, Liu W, Kasmi FE, Wang H, Papikian A, Pastor WA, Moissiard G, Vashisht AA, Dangl JL, Wohlschlegel JA, Jacobsen SE. Arabidopsis AtMORC4 and AtMORC7 Form Nuclear Bodies and Repress a Large Number of Protein-Coding Genes. PLoS Genet 2016; 12:e1005998. [PMID: 27171361 PMCID: PMC4865129 DOI: 10.1371/journal.pgen.1005998] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Accepted: 03/30/2016] [Indexed: 12/30/2022] Open
Abstract
The MORC family of GHKL ATPases are an enigmatic class of proteins with diverse chromatin related functions. In Arabidopsis, AtMORC1, AtMORC2, and AtMORC6 act together in heterodimeric complexes to mediate transcriptional silencing of methylated DNA elements. Here, we studied Arabidopsis AtMORC4 and AtMORC7. We found that, in contrast to AtMORC1,2,6, they act to suppress a wide set of non-methylated protein-coding genes that are enriched for those involved in pathogen response. Furthermore, atmorc4 atmorc7 double mutants show a pathogen response phenotype. We found that AtMORC4 and AtMORC7 form homomeric complexes in vivo and are concentrated in discrete nuclear bodies adjacent to chromocenters. Analysis of an atmorc1,2,4,5,6,7 hextuple mutant demonstrates that transcriptional de-repression is largely uncoupled from changes in DNA methylation in plants devoid of MORC function. However, we also uncover a requirement for MORC in both DNA methylation and silencing at a small but distinct subset of RNA-directed DNA methylation target loci. These regions are characterized by poised transcriptional potential and a low density of sites for symmetric cytosine methylation. These results provide insight into the biological function of MORC proteins in higher eukaryotes.
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Affiliation(s)
- C. Jake Harris
- Department of Molecular, Cell and Developmental Biology, University of California at Los Angeles, Los Angeles, California, United States of America
| | - Dylan Husmann
- Department of Molecular, Cell and Developmental Biology, University of California at Los Angeles, Los Angeles, California, United States of America
| | - Wanlu Liu
- Department of Molecular, Cell and Developmental Biology, University of California at Los Angeles, Los Angeles, California, United States of America
| | - Farid El Kasmi
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Haifeng Wang
- Basic Forestry and Proteomics Research Center, Haixia Institute of Science and Technology (HIST), Fujian Agriculture and Forestry University, Fuzhou, Fujian, China
- Fujian Province Key Laboratory of Plant Virology, Institute of Plant Virology, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China
| | - Ashot Papikian
- Department of Molecular, Cell and Developmental Biology, University of California at Los Angeles, Los Angeles, California, United States of America
| | - William A. Pastor
- Department of Molecular, Cell and Developmental Biology, University of California at Los Angeles, Los Angeles, California, United States of America
| | - Guillaume Moissiard
- Department of Molecular, Cell and Developmental Biology, University of California at Los Angeles, Los Angeles, California, United States of America
| | - Ajay A. Vashisht
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Jeffery L. Dangl
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- Howard Hughes Medical Institute, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - James A. Wohlschlegel
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Steven E. Jacobsen
- Department of Molecular, Cell and Developmental Biology, University of California at Los Angeles, Los Angeles, California, United States of America
- Howard Hughes Medical Institute, University of California at Los Angeles, Los Angeles, California, United States of America
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Csorba T, Kontra L, Burgyán J. viral silencing suppressors: Tools forged to fine-tune host-pathogen coexistence. Virology 2015; 479-480:85-103. [DOI: 10.1016/j.virol.2015.02.028] [Citation(s) in RCA: 368] [Impact Index Per Article: 40.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Revised: 01/31/2015] [Accepted: 02/16/2015] [Indexed: 12/27/2022]
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Abstract
Understanding molecular mechanisms of transcriptional and posttranscriptional gene silencing pathways in plants over the past decades has led to development of tools and methods for silencing a target gene in various plant species. In this review chapter, both the recent understanding of molecular basis of gene silencing pathways and advances in various widely used gene silencing methods are compiled. We also discuss the salient features of the different methods like RNA interference (RNAi) and virus-induced gene silencing (VIGS) and highlight their advantages and disadvantages. Gene silencing technology is constantly progressing as reflected by rapidly emerging new methods. A succinct discussion on the recently developed methods like microRNA-mediated virus-induced gene silencing (MIR-VIGS) and microRNA-induced gene silencing (MIGS) is also provided. One major bottleneck in gene silencing approaches has been the associated off-target silencing. The other hurdle has been the lack of a universal approach that can be applied to all plants. For example, we face hurdles like incompatibility of VIGS vectors with the host and inability to use MIGS for plant species which are not easily transformable. However, the overwhelming research in this direction reflects the scope for overcoming the short comings of gene silencing technology.
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Affiliation(s)
- Prachi Pandey
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, #10531, New Delhi, 110067, India
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21
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Niu D, Wang Z, Wang S, Qiao L, Zhao H. Profiling of small RNAs involved in plant-pathogen interactions. Methods Mol Biol 2015; 1287:61-79. [PMID: 25740356 DOI: 10.1007/978-1-4939-2453-0_4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Small RNA (sRNA)-mediated gene silencing is an important gene expression regulatory mechanism conserved in eukaryotes. Such sRNAs, first discovered in plants, are involved in diverse biological processes. In plants, sRNAs participate in many growth and developmental processes, such as embryo development, seed germination, flowering, hormone synthesis and distribution, and nutrient assimilation. However, the significance of sRNA in shaping the relationship between plants and their symbiotic microbes or pathogens has been underestimated. Recent progress in profiling sRNA, especially advances in next-generation sequencing technology, has revealed its extensive and complicated involvement in interactions between plants and viruses, bacteria, and fungi. In this review, we will summarize recent findings regarding sRNA in plant-pathogen interactions.
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Affiliation(s)
- Dongdong Niu
- Department of Plant Pathology, College of Plant Protection, Nanjing Agricultural University, Xuanwu, Nanjing, Jiangsu, 210095, China
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22
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Di Nicola E, Tavazza M, Lucioli A, Salandri L, Ilardi V. Robust RNA silencing-mediated resistance to Plum pox virus under variable abiotic and biotic conditions. MOLECULAR PLANT PATHOLOGY 2014; 15:841-7. [PMID: 25346969 PMCID: PMC6638643 DOI: 10.1111/mpp.12132] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Some abiotic and biotic conditions are known to have a negative impact on post-transcriptional gene silencing (PTGS), thus representing a potential concern for the production of stable engineered virus resistance traits. However, depending on the strategy followed to achieve PTGS of the transgene, different responses to external conditions can be expected. In the present study, we utilized the Nicotiana benthamiana–Plum pox virus (PPV) pathosystem to evaluate in detail the stability of intron-hairpin(ihp)-mediated virus resistance under conditions known to adversely affect PTGS. The ihp plants grown at low or high temperatures were fully resistant to multiple PPV challenges, different PPV inoculum concentrations and even to a PPV isolate differing from the ihp construct by more than 28% at the nucleotide level. In addition, infections of ihp plants with viruses belonging to Cucumovirus, Potyvirus or Tombusvirus, all known to affect PTGS at different steps, were not able to defeat PPV resistance. Low temperatures did not affect the accumulation of transgenic small interfering RNAs (siRNAs), whereas a clear increase in the amount of siRNAs was observed during infections sustained by Cucumber mosaic virus and Potato virus Y. Our results show that the above stress factors do not represent an important concern for the production,through ihp-PTGS technology, of transgenic plants having robust virus resistance traits.
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23
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Okano Y, Senshu H, Hashimoto M, Neriya Y, Netsu O, Minato N, Yoshida T, Maejima K, Oshima K, Komatsu K, Yamaji Y, Namba S. In Planta Recognition of a Double-Stranded RNA Synthesis Protein Complex by a Potexviral RNA Silencing Suppressor. THE PLANT CELL 2014; 26:2168-2183. [PMID: 24879427 PMCID: PMC4079376 DOI: 10.1105/tpc.113.120535] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Revised: 04/23/2014] [Accepted: 05/09/2014] [Indexed: 05/22/2023]
Abstract
RNA silencing plays an important antiviral role in plants and invertebrates. To counteract antiviral RNA silencing, most plant viruses have evolved viral suppressors of RNA silencing (VSRs). TRIPLE GENE BLOCK PROTEIN1 (TGBp1) of potexviruses is a well-characterized VSR, but the detailed mechanism by which it suppresses RNA silencing remains unclear. We demonstrate that transgenic expression of TGBp1 of plantago asiatica mosaic virus (PlAMV) induced developmental abnormalities in Arabidopsis thaliana similar to those observed in mutants of SUPPRESSOR OF GENE SILENCING3 (SGS3) and RNA-DEPENDENT RNA POLYMERASE6 (RDR6) required for the trans-acting small interfering RNA synthesis pathway. PlAMV-TGBp1 inhibits SGS3/RDR6-dependent double-stranded RNA synthesis in the trans-acting small interfering RNA pathway. TGBp1 interacts with SGS3 and RDR6 and coaggregates with SGS3/RDR6 bodies, which are normally dispersed in the cytoplasm. In addition, TGBp1 forms homooligomers, whose formation coincides with TGBp1 aggregation with SGS3/RDR6 bodies. These results reveal the detailed molecular function of TGBp1 as a VSR and shed new light on the SGS3/RDR6-dependent double-stranded RNA synthesis pathway as another general target of VSRs.
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Affiliation(s)
- Yukari Okano
- Laboratory of Plant Pathology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Hiroko Senshu
- Laboratory of Plant Pathology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Masayoshi Hashimoto
- Laboratory of Plant Pathology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Yutaro Neriya
- Laboratory of Plant Pathology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Osamu Netsu
- Laboratory of Plant Pathology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Nami Minato
- Laboratory of Plant Pathology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Tetsuya Yoshida
- Laboratory of Plant Pathology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Kensaku Maejima
- Laboratory of Plant Pathology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Kenro Oshima
- Laboratory of Plant Pathology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Ken Komatsu
- Laboratory of Plant Pathology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Yasuyuki Yamaji
- Laboratory of Plant Pathology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Shigetou Namba
- Laboratory of Plant Pathology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
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Yoshikawa M. Biogenesis of trans-acting siRNAs, endogenous secondary siRNAs in plants. Genes Genet Syst 2014; 88:77-84. [PMID: 23832299 DOI: 10.1266/ggs.88.77] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Trans-acting small interfering RNAs (tasiRNAs) are plant-specific endogenous siRNAs that control non-identical mRNAs via cleavage. The production of tasiRNAs is triggered by cleavage of capped and polyadenylated primary TAS transcripts (pri-TASs) by specific miRNAs. Following miRNA-directed cleavage, either 5' or 3' cleavage fragments are converted into double-stranded RNAs (dsRNAs) by RNA-DEPENDENT RNA POLYMERASE 6. The dsRNAs are processed to tasiRNAs by DICER-LIKE 4 in a phasing manner. There are two forms of pri-TASs; One has a single miRNA target site that is targeted by 22-nucleotide microRNAs, and the other has two miR390 target sites. Secondary siRNAs that are important for the amplification of RNA silencing are defined as siRNAs whose production is initiated by the cleavage of primary small RNA-containing RNA-induced silencing complexes. Thus, tasiRNA production is a model system of secondary siRNA production in plants. This review focuses on the production of tasiRNAs that are endogenous secondary siRNAs.
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Affiliation(s)
- Manabu Yoshikawa
- Division of Plant Sciences, National Institute of Agrobiological Sciences, Kannondai 2-1-2, Tsukuba, Ibaraki 305-8602, Japan.
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25
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Martínez de Alba AE, Elvira-Matelot E, Vaucheret H. Gene silencing in plants: a diversity of pathways. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2013; 1829:1300-8. [PMID: 24185199 DOI: 10.1016/j.bbagrm.2013.10.005] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Revised: 10/22/2013] [Accepted: 10/24/2013] [Indexed: 10/26/2022]
Abstract
Eukaryotic organisms have evolved a variety of gene silencing pathways in which small RNAs, 20- to 30-nucleotides in length, repress the expression of sequence homologous genes at the transcriptional or post-transcriptional levels. In plants, RNA silencing pathways play important roles in regulating development and response to both biotic and abiotic stresses. The molecular basis of these complex and interconnected pathways has emerged only in recent years with the identification of many of the genes necessary for the biogenesis and action of small RNAs. This review covers the diversity of RNA silencing pathways identified in plants.
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Peláez P, Sanchez F. Small RNAs in plant defense responses during viral and bacterial interactions: similarities and differences. FRONTIERS IN PLANT SCIENCE 2013; 4:343. [PMID: 24046772 PMCID: PMC3763480 DOI: 10.3389/fpls.2013.00343] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Accepted: 08/14/2013] [Indexed: 05/20/2023]
Abstract
Small non-coding RNAs constitute an important class of gene expression regulators that control different biological processes in most eukaryotes. In plants, several small RNA (sRNA) silencing pathways have evolved to produce a wide range of small RNAs with specialized functions. Evidence for the diverse mode of action of the small RNA pathways has been highlighted during plant-microbe interactions. Host sRNAs and small RNA silencing pathways have been recognized as essential components of plant immunity. One way plants respond and defend against pathogen infections is through the small RNA silencing immune system. To deal with plant defense responses, pathogens have evolved sophisticated mechanisms to avoid and counterattack this defense strategy. The relevance of the small RNA-mediated plant defense responses during viral infections has been well-established. Recent evidence points out its importance also during plant-bacteria interactions. Herein, this review discusses recent findings, similarities and differences about the small RNA-mediated arms race between plants and these two groups of microbes, including the small RNA silencing pathway components that contribute to plant immune responses, the pathogen-responsive endogenous sRNAs and the pathogen-delivered effector proteins.
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Affiliation(s)
| | - Federico Sanchez
- *Correspondence: Federico Sanchez, Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Avenida Universidad 2001, 62210 Cuernavaca, Morelos, México e-mail:
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27
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Pontes O, Vitins A, Ream TS, Hong E, Pikaard CS, Costa-Nunes P. Intersection of small RNA pathways in Arabidopsis thaliana sub-nuclear domains. PLoS One 2013; 8:e65652. [PMID: 23776518 PMCID: PMC3680462 DOI: 10.1371/journal.pone.0065652] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2012] [Accepted: 04/25/2013] [Indexed: 12/22/2022] Open
Abstract
In Arabidopsis thaliana, functionally diverse small RNA (smRNA) pathways bring about decreased RNA accumulation of target genes via several different mechanisms. Cytological experiments have suggested that the processing of microRNAs (miRNAs) and heterochromatic small interfering RNAs (hc-siRNAs) occurs within a specific nuclear domain that can present Cajal Body (CB) characteristics. It is unclear whether single or multiple smRNA-related domains are found within the same CB and how specialization of the smRNA pathways is determined within this specific sub-compartment. To ascertain whether nuclear smRNA centers are spatially related, we localized key proteins required for siRNA or miRNA biogenesis by immunofluorescence analysis. The intranuclear distribution of the proteins revealed that hc-siRNA, miRNA and trans-acting siRNA (ta-siRNA) pathway proteins accumulate and colocalize within a sub-nuclear structure in the nucleolar periphery. Furthermore, colocalization of miRNA- and siRNA-pathway members with CB markers, and reduced wild-type localization patterns in CB mutants indicates that proper nuclear localization of these proteins requires CB integrity. We hypothesize that these nuclear domains could be important for RNA silencing and may partially explain the functional redundancies and interactions among components of the same protein family. The CB may be the place in the nucleus where Dicer-generated smRNA precursors are processed and assigned to a specific pathway, and where storage, recycling or assembly of RNA interference components takes place.
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Affiliation(s)
- Olga Pontes
- Department of Biology, University of New Mexico, Albuquerque, New Mexico, United States of America.
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3' fragment of miR173-programmed RISC-cleaved RNA is protected from degradation in a complex with RISC and SGS3. Proc Natl Acad Sci U S A 2013; 110:4117-22. [PMID: 23417299 DOI: 10.1073/pnas.1217050110] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
trans-acting small interfering RNAs (tasiRNAs) are plant-specific endogenous siRNAs produced via a unique pathway whose first step is the microRNA (miRNA)-programmed RNA-induced silencing complex (RISC)-mediated cleavage of tasiRNA gene (TAS) transcripts. One of the products is subsequently transformed into tasiRNAs by a pathway that requires several factors including SUPPRESSOR OF GENE SILENCING3 (SGS3) and RNA-DEPENDENT RNA POLYMERASE6. Here, using in vitro assembled ARGONAUTE (AGO)1-RISCs, we show that SGS3 is recruited onto RISCs only when they bind target RNA. Following cleavage by miRNA173 (miR173)-programmed RISC, SGS3 was found in complexes containing cleaved TAS2 RNA and RISC. The 3' cleavage fragment (the source of tasiRNAs) was protected from degradation in this complex. Depletion of SGS3 did not affect TAS2 RNA cleavage by miR173-programmed RISC, but did affect the stability of the 3' cleavage fragment. When the 3' nucleotide of 22-nt miR173 was deleted or the corresponding nucleotide in TAS2 RNA was mutated, the complex was not observed and the 3' cleavage fragment was degraded. Importantly, these changes in miR173 or TAS2 RNA are known to lead to a loss of tasiRNA production in vivo. These results suggest that (i) SGS3 associates with AGO1-RISC via the double-stranded RNA formed by the 3'-terminal nucleotides of 22-nt miR173 and corresponding target RNA, which probably protrudes from the AGO1-RISC molecular surface, (ii) SGS3 protects the 3' cleavage fragment of TAS2 RNA from degradation, and (iii) the observed SGS3-dependent stabilization of the 3' fragment of TAS2 RNA is key to tasiRNA production.
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29
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Havecker ER, Wallbridge LM, Fedito P, Hardcastle TJ, Baulcombe DC. Metastable differentially methylated regions within Arabidopsis inbred populations are associated with modified expression of non-coding transcripts. PLoS One 2012; 7:e45242. [PMID: 23028873 PMCID: PMC3447930 DOI: 10.1371/journal.pone.0045242] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2012] [Accepted: 08/17/2012] [Indexed: 01/26/2023] Open
Abstract
Individual plants within a population may vary at both genetic and epigenetic levels. The rate of genetic divergence and its underlying mechanisms is well understood. Less is known about the factors contributing to epigenetic divergence among isogenic populations except that, despite the presence of mechanisms that faithfully maintain epigenetic marks, epigenetic differences are more frequent than genetic variation. Epigenetically divergent stretches of isogenic DNA sequence are called epialleles. Currently, it is not clear why certain regions exhibit variable epigenetic status. We identified and characterised two long RNA transcripts with altered expression and DNA methylation in an ago5 mutant. However, further investigation revealed that these changes were not dependent upon AGO5. Rather, the variable transcription of these loci in Arabidopsis mutant and wild-type populations corresponds to spontaneous differential methylated regions (DMRs) or epialleles. These two DMRs are delineated by RNAs which are highly expressed when the DMR is hypomethylated. Furthermore, they control the expression of 5′ transcriptional start site mRNA variants of nearby protein coding genes. Our data support the recent observations that meiotically stable DMRs exist within inbred populations. We further demonstrate that DMR boundaries can be defined by putative non-coding promoter-associated transcripts.
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Affiliation(s)
- Ericka R. Havecker
- Department of Plant Sciences, University of Cambridge, Cambridge, United Kingdom
| | - Laura M. Wallbridge
- Department of Plant Sciences, University of Cambridge, Cambridge, United Kingdom
| | - Paola Fedito
- BIOMAA, University Mediterranea of Reggio Calabria, Reggio Calabria, Italy
| | - Thomas J. Hardcastle
- Department of Plant Sciences, University of Cambridge, Cambridge, United Kingdom
| | - David C. Baulcombe
- Department of Plant Sciences, University of Cambridge, Cambridge, United Kingdom
- * E-mail:
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Le Masson I, Jauvion V, Bouteiller N, Rivard M, Elmayan T, Vaucheret H. Mutations in the Arabidopsis H3K4me2/3 demethylase JMJ14 suppress posttranscriptional gene silencing by decreasing transgene transcription. THE PLANT CELL 2012; 24:3603-12. [PMID: 23001035 PMCID: PMC3480290 DOI: 10.1105/tpc.112.103119] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Revised: 07/23/2012] [Accepted: 08/29/2012] [Indexed: 05/23/2023]
Abstract
Posttranscriptional gene silencing (PTGS) mediated by sense transgenes (S-PTGS) results in RNA degradation and DNA methylation of the transcribed region. Through a forward genetic screen, a mutant defective in the Histone3 Lysine4 di/trimethyl (H3K4me2/3) demethylase Jumonji-C (JmjC) domain-containing protein14 (JMJ14) was identified. This mutant reactivates various transgenes silenced by S-PTGS and shows reduced Histone3 Lysine9 Lysine14 acetylation (H3K9K14Ac) levels, reduced polymerase II occupancy, reduced transgene transcription, and increased DNA methylation in the promoter region, consistent with the hypothesis that high levels of transcription are required to trigger S-PTGS. The jmj14 mutation also reduces the expression of transgenes that do not trigger S-PTGS. Moreover, expression of transgenes that undergo S-PTGS in a wild-type background is reduced in jmj14 sgs3 double mutants compared with PTGS-deficient sgs3 mutants, indicating that JMJ14 is required for high levels of transcription in a PTGS-independent manner. Whereas endogenous loci regulated by JMJ14 exhibit increased H3K4me2 and H3K4me3 levels in the jmj14 mutant, transgene loci exhibit unchanged H3K4me2 and decreased H3K4me3 levels. Because jmj14 mutations impair PTGS of transgenes expressed under various plant or viral promoters, we hypothesize that JMJ14 demethylation activity is prevented by antagonistic epigenetic marks specifically imposed at transgene loci. Removing JMJ14 likely allows other H3K4 demethylases encoded by the Arabidopsis thaliana genome to act on transgenes and reduce transcription levels, thus preventing the triggering of S-PTGS.
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Lee EK, Cibrian-Jaramillo A, Kolokotronis SO, Katari MS, Stamatakis A, Ott M, Chiu JC, Little DP, Stevenson DW, McCombie WR, Martienssen RA, Coruzzi G, DeSalle R. A functional phylogenomic view of the seed plants. PLoS Genet 2011; 7:e1002411. [PMID: 22194700 PMCID: PMC3240601 DOI: 10.1371/journal.pgen.1002411] [Citation(s) in RCA: 123] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2010] [Accepted: 10/21/2011] [Indexed: 12/01/2022] Open
Abstract
A novel result of the current research is the development and implementation of a unique functional phylogenomic approach that explores the genomic origins of seed plant diversification. We first use 22,833 sets of orthologs from the nuclear genomes of 101 genera across land plants to reconstruct their phylogenetic relationships. One of the more salient results is the resolution of some enigmatic relationships in seed plant phylogeny, such as the placement of Gnetales as sister to the rest of the gymnosperms. In using this novel phylogenomic approach, we were also able to identify overrepresented functional gene ontology categories in genes that provide positive branch support for major nodes prompting new hypotheses for genes associated with the diversification of angiosperms. For example, RNA interference (RNAi) has played a significant role in the divergence of monocots from other angiosperms, which has experimental support in Arabidopsis and rice. This analysis also implied that the second largest subunit of RNA polymerase IV and V (NRPD2) played a prominent role in the divergence of gymnosperms. This hypothesis is supported by the lack of 24nt siRNA in conifers, the maternal control of small RNA in the seeds of flowering plants, and the emergence of double fertilization in angiosperms. Our approach takes advantage of genomic data to define orthologs, reconstruct relationships, and narrow down candidate genes involved in plant evolution within a phylogenomic view of species' diversification.
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Affiliation(s)
- Ernest K. Lee
- Sackler Institute for Comparative Genomics, American Museum of Natural History, New York, New York, United States of America
| | - Angelica Cibrian-Jaramillo
- Sackler Institute for Comparative Genomics, American Museum of Natural History, New York, New York, United States of America
- Cullman Program in Molecular Systematics, The New York Botanical Garden, Bronx, New York, United States of America
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, New York, United States of America
| | - Sergios-Orestis Kolokotronis
- Sackler Institute for Comparative Genomics, American Museum of Natural History, New York, New York, United States of America
| | - Manpreet S. Katari
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, New York, United States of America
| | | | - Michael Ott
- Department of Computer Science, Technische Universität München, Munich, Germany
| | - Joanna C. Chiu
- Department of Entomology, University of California Davis, Davis, California, United States of America
| | - Damon P. Little
- Cullman Program in Molecular Systematics, The New York Botanical Garden, Bronx, New York, United States of America
| | - Dennis Wm. Stevenson
- Cullman Program in Molecular Systematics, The New York Botanical Garden, Bronx, New York, United States of America
| | - W. Richard McCombie
- Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, United States of America
| | - Robert A. Martienssen
- Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, United States of America
| | - Gloria Coruzzi
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, New York, United States of America
| | - Rob DeSalle
- Sackler Institute for Comparative Genomics, American Museum of Natural History, New York, New York, United States of America
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Melnyk CW, Molnar A, Baulcombe DC. Intercellular and systemic movement of RNA silencing signals. EMBO J 2011; 30:3553-63. [PMID: 21878996 DOI: 10.1038/emboj.2011.274] [Citation(s) in RCA: 204] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Accepted: 07/19/2011] [Indexed: 12/17/2022] Open
Abstract
In most eukaryotes, double-stranded RNA is processed into small RNAs that are potent regulators of gene expression. This gene silencing process is known as RNA silencing or RNA interference (RNAi) and, in plants and nematodes, it is associated with the production of a mobile signal that can travel from cell-to-cell and over long distances. The sequence-specific nature of systemic RNA silencing indicates that a nucleic acid is a component of the signalling complex. Recent work has shed light on the mobile RNA species, the genes involved in the production and transport of the signal. This review discusses the advances in systemic RNAi and presents the current challenges and questions in this rapidly evolving field.
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Domier LL, Hobbs HA, McCoppin NK, Bowen CR, Steinlage TA, Chang S, Wang Y, Hartman GL. Multiple loci condition seed transmission of soybean mosaic virus (SMV) and SMV-induced seed coat mottling in soybean. PHYTOPATHOLOGY 2011; 101:750-6. [PMID: 21561316 DOI: 10.1094/phyto-09-10-0239] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Infection of soybean plants with Soybean mosaic virus (SMV), which is transmitted by aphids and through seed, can cause significant reductions in seed production and quality. Because seedborne infections are the primary sources of inoculum for SMV infections in North America, host-plant resistance to seed transmission can limit the pool of plants that can serve as sources of inoculum. To examine the inheritance of SMV seed transmission in soybean, crosses were made between plant introductions (PIs) with high (PI88799), moderate (PI60279), and low (PI548391) rates of transmission of SMV through seed. In four F(2) populations, SMV seed transmission segregated as if conditioned by two or more genes. Consequently, a recombinant inbred line population was derived from a cross between PIs 88799 and 548391 and evaluated for segregation of SMV seed transmission, seed coat mottling, and simple sequence repeat markers. Chromosomal regions on linkage groups C1 and C2 were significantly associated with both transmission of isolate SMV 413 through seed and SMV-induced seed coat mottling, and explained ≈42.8 and 46.4% of the variability in these two traits, respectively. Chromosomal regions associated with seed transmission and seed coat mottling contained homologues of Arabidopsis genes DCL3 and RDR6, which encode enzymes involved in RNA-mediated transcriptional and posttranscriptional gene silencing.
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Affiliation(s)
- Leslie L Domier
- United States Department of Agriculture-Agricultural Research Service and Department of Crop Sciences, University of Illinois, Urbana 61801.
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Vogel F, Hofius D, Paulus KE, Jungkunz I, Sonnewald U. The second face of a known player: Arabidopsis silencing suppressor AtXRN4 acts organ-specifically. THE NEW PHYTOLOGIST 2011; 189:484-493. [PMID: 21039560 DOI: 10.1111/j.1469-8137.2010.03482.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Plant viruses exploit the symplastic transport pathway provided by plasmodesmata by encoding for specialized movement proteins, which interact with host factors to enable viral intracellular and intercellular spread. Stable expression of the Potato leaf roll virus movement protein MP17 in Arabidopsis results in a carbohydrate export block and stunted growth. To identify host factors essential for viral infection, we screened a progeny population of EMS (ethyl methanesulfonate)-mutagenized Arabidopsis expressing a MP17:GFP fusion for suppressor mutants with restored wild type-like phenotype. Two suppressor mutants showed decreased susceptibility against Turnip mosaic virus and post-transcriptional silencing of MP17:GFP RNA in source leaves. Map based cloning identified in both lines mutations in XRN4 (Exoribonuclease 4), which was previously described as a suppressor of transgene silencing in source leaves. Importantly, silencing of MP17:GFP was not present in cotyledons and roots of the two suppressor mutants, which was confirmed in a third xrn4 T-DNA knock out line. Subsequent analysis of MP17:GFP transcript stability in xrn2 and xrn3 mutants indicated an essential role of AtXRN2 for silencing suppression in roots/cotyledons while AtXRN3 appears to act similar to AtXRN4 in source leaves, only. Overall, these findings point towards an organ-specific regulation of gene silencing in Arabidopsis.
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Affiliation(s)
- Florian Vogel
- Friedrich-Alexander Universität Erlangen-Nürnberg, Staudtstrasse 5, D-91058 Erlangen Germany.
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Abstract
Small RNAs directly or indirectly impact nearly every biological process in eukaryotic cells. To perform their myriad roles, not only must precise small RNA species be generated, but they must also be loaded into specific effector complexes called RNA-induced silencing complexes (RISCs). Argonaute proteins form the core of RISCs and different members of this large family have specific expression patterns, protein binding partners and biochemical capabilities. In this Review, we explore the mechanisms that pair specific small RNA strands with their partner proteins, with an eye towards the substantial progress that has been recently made in understanding the sorting of the major small RNA classes - microRNAs (miRNAs) and small interfering RNAs (siRNAs) - in plants and animals.
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Affiliation(s)
- Benjamin Czech
- Watson School of Biological Sciences, Howard Hughes Medical Institute, Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, New York 11724, USA
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Jauvion V, Elmayan T, Vaucheret H. The conserved RNA trafficking proteins HPR1 and TEX1 are involved in the production of endogenous and exogenous small interfering RNA in Arabidopsis. THE PLANT CELL 2010; 22:2697-709. [PMID: 20798330 PMCID: PMC2947180 DOI: 10.1105/tpc.110.076638] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2010] [Revised: 07/27/2010] [Accepted: 08/05/2010] [Indexed: 05/18/2023]
Abstract
We previously identified Arabidopsis thaliana mutants defective in sense transgene posttranscriptional gene silencing (S-PTGS) that defined six loci; here, we describe mutants that define nine additional loci, including HYPER RECOMBINATION1 (HPR1), SILENCING DEFECTIVE3 (SDE3), and SDE5. Our analyses extend previous findings by showing that the requirement for the putative RNA helicase SDE3 is inversely proportional to the strength of the PTGS inducer and that the putative RNA trafficking protein SDE5 is an essential component of the trans-acting small interfering RNA (tasiRNA) pathway and is required for S-PTGS but not inverted repeat transgene-mediated PTGS (IR-PTGS). Our screen also identified HPR1 as a PTGS actor. We show that hpr1 mutations negatively impact S-PTGS, IR-PTGS, and tasiRNA pathways, resulting in increased accumulation of siRNA precursors and decreased accumulation of mature siRNA. In animals, HPR1/THO1 is a member of the conserved RNA trafficking THO/TREX complex, which also includes TEX1/THO3. We show that tex1 mutants, like hpr1 mutants, impact TAS precursor and mature tasiRNA levels, suggesting that a THO/TREX complex exists in plants and that this complex is important for the integrity of the tasiRNA pathway. We propose that both HPR1 and TEX1 participate in the trafficking of siRNA precursors to the ARGONAUTE catalytic center.
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Rausin G, Tillemans V, Stankovic N, Hanikenne M, Motte P. Dynamic nucleocytoplasmic shuttling of an Arabidopsis SR splicing factor: role of the RNA-binding domains. PLANT PHYSIOLOGY 2010; 153:273-84. [PMID: 20237019 PMCID: PMC2862426 DOI: 10.1104/pp.110.154740] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2010] [Accepted: 03/11/2010] [Indexed: 05/22/2023]
Abstract
Serine/arginine-rich (SR) proteins are essential nuclear-localized splicing factors. We have investigated the dynamic subcellular distribution of the Arabidopsis (Arabidopsis thaliana) RSZp22 protein, a homolog of the human 9G8 SR factor. Little is known about the determinants underlying the control of plant SR protein dynamics, and so far most studies relied on ectopic transient overexpression. Here, we provide a detailed analysis of the RSZp22 expression profile and describe its nucleocytoplasmic shuttling properties in specific cell types. Comparison of transient ectopic- and stable tissue-specific expression highlights the advantages of both approaches for nuclear protein dynamic studies. By site-directed mutagenesis of RSZp22 RNA-binding sequences, we show that functional RNA recognition motif RNP1 and zinc-knuckle are dispensable for the exclusive protein nuclear localization and speckle-like distribution. Fluorescence resonance energy transfer imaging also revealed that these motifs are implicated in RSZp22 molecular interactions. Furthermore, the RNA-binding motif mutants are defective for their export through the CRM1/XPO1/Exportin-1 receptor pathway but retain nucleocytoplasmic mobility. Moreover, our data suggest that CRM1 is a putative export receptor for mRNPs in plants.
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38
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Dunoyer P, Brosnan CA, Schott G, Wang Y, Jay F, Alioua A, Himber C, Voinnet O. An endogenous, systemic RNAi pathway in plants. EMBO J 2010; 29:1699-712. [PMID: 20414198 DOI: 10.1038/emboj.2010.65] [Citation(s) in RCA: 170] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2010] [Accepted: 03/22/2010] [Indexed: 11/09/2022] Open
Abstract
Recent work on metazoans has uncovered the existence of an endogenous RNA-silencing pathway that functionally recapitulates the effects of experimental RNA interference (RNAi) used for gene knockdown in organisms such as Caenorhabditis elegans and Drosophila. The endogenous short interfering (si)RNA involved in this pathway are processed by Dicer-like nucleases from genomic loci re-arranged to form extended inverted repeats (IRs) that produce perfect or near-perfect dsRNA molecules. Although such IR loci are commonly detected in plant genomes, their genetics, evolution and potential contribution to plant biology through endogenous silencing have remained largely unexplored. Through an exhaustive analysis performed using Arabidopsis, we provide here evidence that at least two such endogenous IRs are genetically virtually indistinguishable from the transgene constructs commonly used for RNAi in plants. We show how these loci can be useful probes of the cellular mechanism and fluidity of RNA-silencing pathways in plants, and provide evidence that they may arise and disappear on an ecotype scale, show highly cell-specific expression patterns and respond to various stresses. IR loci thus have the potential to act as molecular sensors of the local environments found within distinct ecological plant niches. We further show that the various siRNA size classes produced by at least one of these IR loci are functionally loaded into cognate effector proteins and mediate both post-transcriptional gene silencing and RNA-directed DNA methylation (RdDM) of endogenous as well as exogenous targets. Finally, and as previously reported during plant experimental RNAi, we provide evidence that endogenous IR-derived siRNAs of all size classes are not cell-autonomous and can be transported through graft junctions over long distances, in target tissues where they are functional, at least in mediating RdDM. Collectively, these results define the existence of a bona fide, endogenous and systemic RNAi pathway in plants that may have implications in adaptation, epiallelism and trans-generational memory.
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Affiliation(s)
- Patrice Dunoyer
- Institut de Biologie Moléculaire des Plantes du CNRS, UPR2357, Université de Strasbourg, Strasbourg Cedex, France.
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Abstract
Small RNAs associated with post-transcriptional gene silencing were first discovered in plants in 1999. Although this study marked the beginning of small RNA biology in plants, the sequence of the Arabidopsis genome and related genomic resources that were soon to become available to the Arabidopsis community launched the research on small RNAs at a remarkable pace. In 2000, when the genetic blueprint of the first plant species was revealed, the tens of thousands of endogenous small RNA species as we know today remained hidden features of the genome. However, the subsequent 10 years have witnessed an explosion of our knowledge of endogenous small RNAs: their widespread existence, diversity, biogenesis, mode of action and biological functions. As key sequence-specific regulators of gene expression in the nucleus and the cytoplasm, small RNAs influence almost all aspects of plant biology. Because of the extensive conservation of mechanisms concerning the biogenesis and molecular actions of small RNAs, research in the model plant Arabidopsis has contributed vital knowledge to the small RNA field in general. Our knowledge of small RNAs gained primarily from Arabidopsis has also led to the invention of effective gene knock-down technologies that are applicable to diverse plant species, including crop plants. Here, I attempt to recount the developments of the small RNA field in the pre- and post-genomic era, in celebration of the 10th anniversary of the completion of the first plant genome.
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Affiliation(s)
- Xuemei Chen
- Department of Botany and Plant Sciences, Institute of Integrative Genome Biology, University of California, Riverside, CA 92521, USA.
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40
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Desai PN, Shrivastava N, Padh H. Production of heterologous proteins in plants: strategies for optimal expression. Biotechnol Adv 2010; 28:427-35. [PMID: 20152894 DOI: 10.1016/j.biotechadv.2010.01.005] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2009] [Revised: 01/01/2010] [Accepted: 01/25/2010] [Indexed: 11/25/2022]
Abstract
Plants are a promising expression system for the production of heterologous proteins, especially therapeutic proteins. Currently the majority of therapeutic proteins are produced in mammalian cell lines or bacteria. In a few cases insects, yeast and fungi have been developed for production of human proteins. However, these expression systems have limitations in terms of suitability, cost, scalability, purification and post-translational modifications. Therefore, alternative expression systems are being developed in transgenic animals and transgenic plants. Transgenic plants could provide an attractive alternative in terms of low production cost and lower capital investment in infrastructure, and with appropriate post-translational modifications. The potential of plants as an expression host has not been capitalized, primarily due to lower level of expression of transgenes in plants. The present review will evaluate the rate limiting steps of plant expression systems and suggest strategies to optimize protein expression at each of the steps: gene integration, transcription, translation and protein accumulation.
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Affiliation(s)
- Priti N Desai
- B. V. Patel Pharmaceutical Education and Research Development Centre, Ahmedabad, India
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Yu B, Wang H. Translational Inhibition by MicroRNAs in Plants. MIRNA REGULATION OF THE TRANSLATIONAL MACHINERY 2010; 50:41-57. [DOI: 10.1007/978-3-642-03103-8_3] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Wypijewski K, Hornyik C, Shaw JA, Stephens J, Goraczniak R, Gunderson SI, Lacomme C. Ectopic 5' splice sites inhibit gene expression by engaging RNA surveillance and silencing pathways in plants. PLANT PHYSIOLOGY 2009; 151:955-65. [PMID: 19666706 PMCID: PMC2754638 DOI: 10.1104/pp.109.139733] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2009] [Accepted: 08/04/2009] [Indexed: 05/25/2023]
Abstract
The quality control of mRNA maturation is a highly regulated process that surveys pre-mRNA integrity and eliminates improperly matured pre-mRNAs. In nature, certain viruses regulate the expression of their genes by hijacking the endogenous RNA quality control machinery. We demonstrate that the inclusion of 5' splice sites within the 3'-untranslated region of a reporter gene in plants alters the pre-mRNA cleavage and polyadenylation process, resulting in pre-mRNA degradation, exemplifying a regulatory mechanism conserved between kingdoms. Altered pre-mRNA processing was associated with an inhibition of homologous gene expression in trans and the preferential accumulation of 24-nucleotide (nt) short-interfering RNAs (siRNAs) as opposed to 21-nt siRNA subspecies, suggesting that degradation of the aberrant pre-mRNA involves the silencing machinery. However, gene expression was not restored by coexpression of a silencing suppressor or in an RNA-dependent RNA polymerase (RDR6)-deficient background despite reduced 24-nt siRNA accumulation. Our data highlight a complex cross talk between the quality control RNA machinery, 3'-end pre-mRNA maturation, and RNA-silencing pathways capable of discriminating among different types of aberrant RNAs.
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Affiliation(s)
- Krzysztof Wypijewski
- Plant Pathology Department, Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, United Kingdom
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Aliyari R, Ding SW. RNA-based viral immunity initiated by the Dicer family of host immune receptors. Immunol Rev 2009; 227:176-88. [PMID: 19120484 DOI: 10.1111/j.1600-065x.2008.00722.x] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Suppression of viral infection by RNA in a nucleotide sequence homology-dependent manner was first reported in plants in early 1990 s. Studies in the past 15 years have established a completely new RNA-based immune system against viruses that is mechanistically related to RNA silencing or RNA interference (RNAi). This viral immunity begins with recognition of viral double-stranded or structured RNA by the Dicer nuclease family of host immune receptors. In fungi, plants and invertebrates, the viral RNA trigger is processed into small interfering RNAs (siRNAs) to direct specific silencing of the homologous viral genomic and/or messenger RNAs by an RNaseH-like Argonaute protein. Deep sequencing of virus-derived siRNAs indicates that the immunity against viruses with a positive-strand RNA genome is induced by Dicer recognition of dsRNA formed during the initiation of viral progeny (+)RNA synthesis. The RNA-based immune pathway in these organisms overlaps the canonical dsRNA-siRNA pathway of RNAi and may require amplification of viral siRNAs by host RNA-dependent RNA polymerase in plants and nematodes. Production of virus-derived small RNAs is undetectable in mammalian cells infected with RNA viruses. However, infection of mammals with several nucleus-replicating DNA viruses induces production of virus-derived microRNAs capable of silencing host and viral mRNAs as found for viral siRNAs. Remarkably, recent studies indicate that prokaryotes also produce virus-derived small RNAs known as CRISPR RNAs to guide antiviral defense in a manner that has yet to be defined. In this article, we review the recent progress on the identification and mechanism of the key components including viral sensors, viral triggers, effectors, and amplifiers, of the small RNA-directed viral immunity. We also highlight some of the many unresolved questions.
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Affiliation(s)
- Roghiyh Aliyari
- Department of Plant Pathology & Microbiology, Institute for Integrative Genome Biology, University of California, Riverside, CA 92521, USA
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44
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ARGONAUTE 1 homeostasis invokes the coordinate action of the microRNA and siRNA pathways. EMBO Rep 2009; 10:521-6. [PMID: 19343050 DOI: 10.1038/embor.2009.32] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2008] [Revised: 01/29/2009] [Accepted: 02/09/2009] [Indexed: 01/01/2023] Open
Abstract
ARGONAUTE 1 (AGO1) slices endogenous messenger RNAs (mRNAs) during both microRNA (miRNA)- and short interfering RNA (siRNA)-guided post-transcriptional silencing. We have previously reported that AGO1 homeostasis is maintained through the repressive action of miR168 on AGO1 mRNA and the stabilizing effect of AGO1 protein on miR168, but siRNA-mediated AGO1 regulation has not been reported. Here, we show that AGO1-derived siRNAs trigger RNA DEPENDENT RNA POLYMERASE 6 (RDR6)-, SUPPRESSOR OF GENE SILENCING 3 (SGS3)- and SILENCING DEFECTIVE 5 (SDE5)-dependent AGO1 silencing, which also requires DICER-LIKE 2 (DCL2) and DCL4. By varying the efficacy of miR168-guided AGO1 mRNA cleavage, we show that siRNA-mediated AGO1 silencing depends on correct miRNA targeting, pointing to coordinated regulatory actions of the miRNA and siRNA pathways during the maintenance of AGO1 homeostasis. Finally, our results reveal that dcl2, dcl3 and dcl4 mutations similarly affect post-transcriptional gene silencing (PTGS) mediated by a sense transgene and PTGS mediated by inverted repeats, validating the branched pathway model proposed previously.
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Lu R, Yigit E, Li WX, Ding SW. An RIG-I-Like RNA helicase mediates antiviral RNAi downstream of viral siRNA biogenesis in Caenorhabditis elegans. PLoS Pathog 2009; 5:e1000286. [PMID: 19197349 PMCID: PMC2629121 DOI: 10.1371/journal.ppat.1000286] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2008] [Accepted: 01/05/2009] [Indexed: 01/08/2023] Open
Abstract
Dicer ribonucleases of plants and invertebrate animals including Caenorhabditis elegans recognize and process a viral RNA trigger into virus-derived small interfering RNAs (siRNAs) to guide specific viral immunity by Argonaute-dependent RNA interference (RNAi). C. elegans also encodes three Dicer-related helicase (drh) genes closely related to the RIG-I-like RNA helicase receptors which initiate broad-spectrum innate immunity against RNA viruses in mammals. Here we developed a transgenic C. elegans strain that expressed intense green fluorescence from a chromosomally integrated flock house virus replicon only after knockdown or knockout of a gene required for antiviral RNAi. Use of the reporter nematode strain in a feeding RNAi screen identified drh-1 as an essential component of the antiviral RNAi pathway. However, RNAi induced by either exogenous dsRNA or the viral replicon was enhanced in drh-2 mutant nematodes, whereas exogenous RNAi was essentially unaltered in drh-1 mutant nematodes, indicating that exogenous and antiviral RNAi pathways are genetically distinct. Genetic epistatic analysis shows that drh-1 acts downstream of virus sensing and viral siRNA biogenesis to mediate specific antiviral RNAi. Notably, we found that two members of the substantially expanded subfamily of Argonautes specific to C. elegans control parallel antiviral RNAi pathways. These findings demonstrate both conserved and unique strategies of C. elegans in antiviral defense. The genome of Caenorhabditis elegans encodes three Dicer-related helicases (DRHs) highly homologous to the DExD/H box helicase domain found in two distinct families of virus sensors, Dicer ribonucleases and RIG-I-like helicases (RLRs). Dicer initiates the specific, RNAi-mediated viral immunity in plants, fungi and invertebrates by producing virus-derived small interfering RNAs (siRNAs). By contrast, mammalian RLRs trigger interferon production and broad-spectrum viral immunity, although one of the three RLRs may act as both a negative and positive regulator of viral immunity. In this study we developed a transgenic C. elegans strain for high-throughput genetic screens and identified 35 genes including drh-1 that are required for RNAi-mediated viral immunity. Genetic epistatic analyses demonstrate that drh-1 mediates RNAi immunity downstream of the production of viral siRNAs. Notably, we found that drh-2 functions as a negative regulator of the viral immunity. Thus, both nematode DRHs and mammalian RLRs participate in antiviral immune responses. Unlike mammalian RLRs, however, nematode DRH-1 employs an RNAi effector mechanism and is unlikely to be involved in direct virus sensing.
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Affiliation(s)
- Rui Lu
- Department of Plant Pathology & Microbiology, University of California, Riverside, California, United States of America
| | - Erbay Yigit
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Wan-Xiang Li
- Department of Plant Pathology & Microbiology, University of California, Riverside, California, United States of America
| | - Shou-Wei Ding
- Department of Plant Pathology & Microbiology, University of California, Riverside, California, United States of America
- * E-mail:
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Elmayan T, Adenot X, Gissot L, Lauressergues D, Gy I, Vaucheret H. A neomorphic sgs3 allele stabilizing miRNA cleavage products reveals that SGS3 acts as a homodimer. FEBS J 2009; 276:835-44. [DOI: 10.1111/j.1742-4658.2008.06828.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Ramachandran V, Chen X. Small RNA metabolism in Arabidopsis. TRENDS IN PLANT SCIENCE 2008; 13:368-74. [PMID: 18501663 PMCID: PMC2569976 DOI: 10.1016/j.tplants.2008.03.008] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2008] [Revised: 03/21/2008] [Accepted: 03/28/2008] [Indexed: 05/20/2023]
Abstract
The Arabidopsis genome encodes two major classes of 20-24-nucleotide riboregulators: microRNAs and small interfering RNAs. These small RNAs act as sequence-specific repressors of target gene expression, either at the transcriptional level through DNA and/or histone methylation or at the post-transcriptional level through transcript cleavage or translational inhibition. Small RNAs are processed from precursor RNAs by one or more of the four DICER-LIKE RNase III enzymes, modified by HUA ENHANCER 1, a small RNA methyltransferase, and loaded onto an argonaute protein-containing RNA-induced silencing complex. Here, we review the biogenesis of small RNAs, and we discuss the major outstanding questions in small RNA metabolism and function.
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Affiliation(s)
- Vanitharani Ramachandran
- Department of Botany and Plant Sciences, Institute of Integrative Genome Biology, University of California, Riverside, CA 92521, USA
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Abstract
The nucleolus is a multifunctional compartment of the eukaryotic nucleus. Besides its well-recognised role in transcription and processing of ribosomal RNA and the assembly of ribosomal subunits, the nucleolus has functions in the processing and assembly of a variety of RNPs and is involved in cell cycle control and senescence and as a sensor of stress. Historically, nucleoli have been tenuously linked to the biogenesis and, in particular, export of mRNAs in yeast and mammalian cells. Recently, data from plants have extended the functions in which the plant nucleolus is involved to include transcriptional gene silencing as well as mRNA surveillance and nonsense-mediated decay, and mRNA export. The nucleolus in plants may therefore have important roles in the biogenesis and quality control of mRNAs.
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Affiliation(s)
- Anireddy S. N. Reddy
- Department of Biology and Program in Molecular Plant Biology, Colorado State University, Fort Collins, CO 80523 USA
| | - Maxim Golovkin
- Department of Microbiology, Thomas Jefferson University, Philadelphia, PA 19107 USA
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Chen S, Hajirezaei MR, Zanor MI, Hornyik C, Debast S, Lacomme C, Fernie AR, Sonnewald U, Börnke F. RNA interference-mediated repression of sucrose-phosphatase in transgenic potato tubers (Solanum tuberosum) strongly affects the hexose-to-sucrose ratio upon cold storage with only minor effects on total soluble carbohydrate accumulation. PLANT, CELL & ENVIRONMENT 2008; 31:165-176. [PMID: 17999659 DOI: 10.1111/j.1365-3040.2007.01747.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Storage of potato tubers at low temperatures leads to the accumulation of glucose and fructose in a process called 'cold sweetening'. The aim of this work was to investigate the role of sucrose-phosphatase (SPP) in potato tuber carbohydrate metabolism at low temperature (4 degrees C). To this end, RNA interference (RNAi) was used to reduce SPP expression in transgenic potato tubers. Analysis of SPP specific small interfering RNAs (siRNAs), SPP protein accumulation and enzyme activity indicated that SPP silencing in transgenic tubers was stable during the cold treatment. Analysis of soluble carbohydrates showed that in transgenic tubers, cold-induced hexogenesis was inhibited while, despite strongly reduced SPP activity, sucrose levels exceeded wild-type (WT) values four- to fivefold after 34 d of cold treatment. This led to a drastic change in the hexose-to-sucrose ratio from 1.9 in WT tubers to 0.15 to 0.11 in transgenic tubers, while the total amount of soluble sugars was largely unchanged in both genotypes. Sucrose-6(F)-phosphate (Suc6P), the substrate of SPP, accumulated in transgenic tubers in the cold which most likely enables the residual enzyme to operate with maximal catalytic activity in vivo and thus, in the long term, counterbalances reduced SPP activity in the transformants. Northern analysis revealed that cold-induced expression of vacuolar invertase (VI) was blocked in SPP-silenced tubers explaining a reduced sucrose-to-hexose conversion. Suc6P levels were found to negatively correlate with VI expression. A possible role of Suc6P in regulating VI expression is discussed.
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Affiliation(s)
- Shuai Chen
- Friedrich-Alexander-Universität, Lehrstuhl für Biochemie, Staudtstr. 5, 91058 Erlangen, Germany
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