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Qiu X, Wang W, Yang J, Li D, Jiao J, Wang E, Yuan H. Fulvic Acid Promotes Legume-Rhizobium Symbiosis by Stimulating Endogenous Flavonoids Synthesis and Secretion. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2024; 72:6133-6142. [PMID: 38489511 DOI: 10.1021/acs.jafc.3c08837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/17/2024]
Abstract
Fulvic acid (FA) promotes symbiosis between legumes and rhizobia. To elucidate from the aspect of symbiosis, the effects of root irrigation of water-soluble humic materials (WSHM) or foliar spraying of its highly active component, FA, on soybean root exudates and on rhizosphere microorganisms were investigated. As a result, WSHM/FA treatments significantly altered root exudate metabolite composition, and isoflavonoids were identified as key contributors in both treatments compared to the control. Increased expression of genes related to the isoflavonoid biosynthesis were validated by RT-qPCR in both treatments, which notably elevated the synthesis of symbiotic signals genistein, daidzin, coumestrol, and biochanin A. Moreover, the WSHM/FA treatments induced a change in rhizosphere microbial community, coupled with an increase in the relative abundance of rhizobia. Our findings showed that WSHM/FA promotes symbiosis by stimulating the endogenous flavonoid synthesis and leads to rhizobia accumulation in the rhizosphere. This study provides new insights into mechanisms underlying the FA-mediated promotion of symbiosis.
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Affiliation(s)
- Xiaoqian Qiu
- State Key Laboratory of Animal Biotech Breeding and Key Laboratory of Soil Microbiology, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Wenqian Wang
- State Key Laboratory of Animal Biotech Breeding and Key Laboratory of Soil Microbiology, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Jinshui Yang
- State Key Laboratory of Animal Biotech Breeding and Key Laboratory of Soil Microbiology, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Dongmei Li
- State Key Laboratory of Animal Biotech Breeding and Key Laboratory of Soil Microbiology, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Jian Jiao
- State Key Laboratory of Animal Biotech Breeding and Key Laboratory of Soil Microbiology, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Entao Wang
- Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Mexico City 07738, Mexico
| | - Hongli Yuan
- State Key Laboratory of Animal Biotech Breeding and Key Laboratory of Soil Microbiology, College of Biological Sciences, China Agricultural University, Beijing 100193, China
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Li D, Wang W, Peng Y, Qiu X, Yang J, Zhang C, Wang E, Wang X, Yuan H. Soluble humic acid suppresses plant immunity and ethylene to promote soybean nodulation. PLANT, CELL & ENVIRONMENT 2024; 47:871-884. [PMID: 38164043 DOI: 10.1111/pce.14801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Revised: 11/23/2023] [Accepted: 12/17/2023] [Indexed: 01/03/2024]
Abstract
Symbiotic nitrogen fixation (SNF) is a crucial process for nitrogen geochemical cycling and plant-microbe interactions. Water-soluble humic acid (WSHM), an active component of soil humus, has been shown to promote SNF in the legume-rhizobial symbiosis, but its molecular mechanism remains largely unknown. To reveal the SNF-promoting mechanism, we conducted transcriptomic analysis on soybean treated with WSHM. Our findings revealed that up- and downregulated differentially expressed genes (DEGs) were mainly involved in plant cell-wall/membrane formation and plant defence/immunity in the early stage, while the late stage was marked by the flavonoid synthesis and ethylene biosynthetic process. Further study on representative DEGs showed that WSHM could inhibit GmBAK1d-mediated immunity and BR signalling, thereby promoting rhizobial colonisation, infection, and nodulation, while not favoring pathogenic bacteria colonisation on the host plant. Additionally, we also found that the ethylene pathway is necessary for promoting the soybean nodulation by WSHM. This study not only provides a significant advance in our understanding of the molecular mechanism of WSHM in promoting SNF, but also provides evidence of the beneficial interactions among the biostimulator, host plant, and soil microbes, which have not been previously reported.
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Affiliation(s)
- Dongmei Li
- State Key Laboratory of Animal Biotech Breeding, China Agricultural University, Beijing, China
| | - Wenqian Wang
- State Key Laboratory of Animal Biotech Breeding, China Agricultural University, Beijing, China
| | - Yaqi Peng
- State Key Laboratory of Crop Stress Adaptation and Improvement, Henan University, Kaifeng, China
| | - Xiaoqian Qiu
- State Key Laboratory of Animal Biotech Breeding, China Agricultural University, Beijing, China
| | - Jinshui Yang
- State Key Laboratory of Animal Biotech Breeding, China Agricultural University, Beijing, China
| | - Chunting Zhang
- State Key Laboratory of Animal Biotech Breeding, China Agricultural University, Beijing, China
| | - Entao Wang
- Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Mexico City, Mexico
| | - Xuelu Wang
- State Key Laboratory of Crop Stress Adaptation and Improvement, Henan University, Kaifeng, China
| | - Hongli Yuan
- State Key Laboratory of Animal Biotech Breeding, China Agricultural University, Beijing, China
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Popa DG, Lupu C, Constantinescu-Aruxandei D, Oancea F. Humic Substances as Microalgal Biostimulants—Implications for Microalgal Biotechnology. Mar Drugs 2022; 20:md20050327. [PMID: 35621978 PMCID: PMC9143693 DOI: 10.3390/md20050327] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Revised: 05/11/2022] [Accepted: 05/12/2022] [Indexed: 02/01/2023] Open
Abstract
Humic substances (HS) act as biostimulants for terrestrial photosynthetic organisms. Their effects on plants are related to specific HS features: pH and redox buffering activities, (pseudo)emulsifying and surfactant characteristics, capacity to bind metallic ions and to encapsulate labile hydrophobic molecules, ability to adsorb to the wall structures of cells. The specific properties of HS result from the complexity of their supramolecular structure. This structure is more dynamic in aqueous solutions/suspensions than in soil, which enhances the specific characteristics of HS. Therefore, HS effects on microalgae are more pronounced than on terrestrial plants. The reported HS effects on microalgae include increased ionic nutrient availability, improved protection against abiotic stress, including against various chemical pollutants and ionic species of potentially toxic elements, higher accumulation of value-added ingredients, and enhanced bio-flocculation. These HS effects are similar to those on terrestrial plants and could be considered microalgal biostimulant effects. Such biostimulant effects are underutilized in current microalgal biotechnology. This review presents knowledge related to interactions between microalgae and humic substances and analyzes the potential of HS to enhance the productivity and profitability of microalgal biotechnology.
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Affiliation(s)
- Daria Gabriela Popa
- Faculty of Biotechnologies, University of Agronomic Sciences and Veterinary Medicine of Bucharest, Mărăști Blv, No. 59, Sector 1, 011464 Bucharest, Romania;
- Bioproducts Team, Bioresources Department, National Institute for Research & Development in Chemistry and Petrochemistry—ICECHIM, Splaiul Independenței No. 202, Sector 6, 060021 Bucharest, Romania;
| | - Carmen Lupu
- Bioproducts Team, Bioresources Department, National Institute for Research & Development in Chemistry and Petrochemistry—ICECHIM, Splaiul Independenței No. 202, Sector 6, 060021 Bucharest, Romania;
| | - Diana Constantinescu-Aruxandei
- Bioproducts Team, Bioresources Department, National Institute for Research & Development in Chemistry and Petrochemistry—ICECHIM, Splaiul Independenței No. 202, Sector 6, 060021 Bucharest, Romania;
- Correspondence: (D.C.-A.); (F.O.)
| | - Florin Oancea
- Faculty of Biotechnologies, University of Agronomic Sciences and Veterinary Medicine of Bucharest, Mărăști Blv, No. 59, Sector 1, 011464 Bucharest, Romania;
- Bioproducts Team, Bioresources Department, National Institute for Research & Development in Chemistry and Petrochemistry—ICECHIM, Splaiul Independenței No. 202, Sector 6, 060021 Bucharest, Romania;
- Correspondence: (D.C.-A.); (F.O.)
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Kang J, Yin Z, Pei F, Ye Z, Sun Y, Song G, Ge J. Driving factors of nitrogen conversion during chicken manure aerobic composting under penicillin G residue: Quorum sensing and its signaling molecules. BIORESOURCE TECHNOLOGY 2022; 345:126469. [PMID: 34864180 DOI: 10.1016/j.biortech.2021.126469] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Revised: 11/23/2021] [Accepted: 11/27/2021] [Indexed: 06/13/2023]
Abstract
This study explored effects of different concentrations of penicillin G on nitrogen conversion, bacterial community composition, and quorum sensing during chicken manure aerobic composting. After composting, adding penicillin G down-regulated the abundance of 71 genera and up-regulated the abundance of 103 genera. These bacterial genera were mainly Firmicutes and Proteobacteria. 16S rRNA gene sequencing was employed for function prediction, and the results showed that the addition of penicillin G increased nitrification, reduced denitrification. The autoinducer-1 (AI-1), autoinducer-3 (AI-3) and Phr signal molecules further participated in the nitrogen cycle by regulating the population behavior among multiple bacterial genera. In addition, SEM analysis showed that the quorum sensing system negatively regulated the abundance of genus related to the nitrogen conversion during chicken manure aerobic composting. This is a new theoretical analysis of the research on the treatment of hazardous materials.
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Affiliation(s)
- Jie Kang
- Engineering Research Center of Agricultural Microbiology Technology, Ministry of Education, Heilongjiang University, Harbin 150500, China; Key Laboratory of Microbiology, College of Heilongjiang Province, School of Life Sciences, Heilongjiang University, Harbin 150080, China
| | - Ziliang Yin
- Engineering Research Center of Agricultural Microbiology Technology, Ministry of Education, Heilongjiang University, Harbin 150500, China; Key Laboratory of Microbiology, College of Heilongjiang Province, School of Life Sciences, Heilongjiang University, Harbin 150080, China
| | - Fangyi Pei
- Engineering Research Center of Agricultural Microbiology Technology, Ministry of Education, Heilongjiang University, Harbin 150500, China; Key Laboratory of Microbiology, College of Heilongjiang Province, School of Life Sciences, Heilongjiang University, Harbin 150080, China
| | - Zeming Ye
- Engineering Research Center of Agricultural Microbiology Technology, Ministry of Education, Heilongjiang University, Harbin 150500, China; Key Laboratory of Microbiology, College of Heilongjiang Province, School of Life Sciences, Heilongjiang University, Harbin 150080, China
| | - Yangcun Sun
- Engineering Research Center of Agricultural Microbiology Technology, Ministry of Education, Heilongjiang University, Harbin 150500, China; Key Laboratory of Microbiology, College of Heilongjiang Province, School of Life Sciences, Heilongjiang University, Harbin 150080, China
| | - Gang Song
- Engineering Research Center of Agricultural Microbiology Technology, Ministry of Education, Heilongjiang University, Harbin 150500, China; Key Laboratory of Microbiology, College of Heilongjiang Province, School of Life Sciences, Heilongjiang University, Harbin 150080, China
| | - Jingping Ge
- Engineering Research Center of Agricultural Microbiology Technology, Ministry of Education, Heilongjiang University, Harbin 150500, China; Key Laboratory of Microbiology, College of Heilongjiang Province, School of Life Sciences, Heilongjiang University, Harbin 150080, China.
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da Silva MSRDA, Dos Santos BDMS, da Silva CSRDA, da Silva CSRDA, Antunes LFDS, Dos Santos RM, Santos CHB, Rigobelo EC. Humic Substances in Combination With Plant Growth-Promoting Bacteria as an Alternative for Sustainable Agriculture. Front Microbiol 2021; 12:719653. [PMID: 34777275 PMCID: PMC8589081 DOI: 10.3389/fmicb.2021.719653] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Accepted: 09/16/2021] [Indexed: 11/13/2022] Open
Abstract
Plant growth-promoting bacteria (PGPB) and humic substances (HSs) are promising options for reducing the use of pesticides and mineral fertilizers. Although many studies have shown the effects of PGPB and HSs separately, little information is available on plant responses to the combined application of these biostimulants despite the great potential for the simultaneous action of these biological inputs. Thus, the objective of this review is to present an overview of scientific studies that addressed the application of PGPB and HSs to different crops. First, we discuss the effect of these biostimulants on biological nitrogen fixation, the various effects of the inoculation of beneficial bacteria combined with the application of HSs on promoting the growth of nonleguminous plants and how this combination can increase bacterial colonization of plant hosts. We also address the effect of PGPB and HSs on plant responses to abiotic stresses, in addition to discussing the role of HSs in protecting plants against pathogens. There is a lack of studies that address the role of PGPB + HSs in biocontrol. Understanding the factors involved in the promotion of plant growth through the application of PGPB and HSs can assist in the development of efficient biostimulants for agricultural management. This approach has the potential to accelerate the transition from conventional cultivation to sustainable agrosystems.
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Affiliation(s)
| | | | - Camilla Santos Reis de Andrade da Silva
- Department of Soil, Universidade Federal Rural do Rio de Janeiro, Seropédica, Brazil.,National Agrobiology Research Center, Embrapa Agrobiologia, Seropédica, Brazil
| | | | | | | | | | - Everlon Cid Rigobelo
- Department of Agricultural Production Sciences, Universidade Estadual Paulista, Jaboticabal, Brazil
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Evguenieva-Hackenberg E. Riboregulation in bacteria: From general principles to novel mechanisms of the trp attenuator and its sRNA and peptide products. WILEY INTERDISCIPLINARY REVIEWS-RNA 2021; 13:e1696. [PMID: 34651439 DOI: 10.1002/wrna.1696] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Revised: 08/25/2021] [Accepted: 09/10/2021] [Indexed: 12/26/2022]
Abstract
Gene expression strategies ensuring bacterial survival and competitiveness rely on cis- and trans-acting RNA-regulators (riboregulators). Among the cis-acting riboregulators are transcriptional and translational attenuators, and antisense RNAs (asRNAs). The trans-acting riboregulators are small RNAs (sRNAs) that bind proteins or base pairs with other RNAs. This classification is artificial since some regulatory RNAs act both in cis and in trans, or function in addition as small mRNAs. A prominent example is the archetypical, ribosome-dependent attenuator of tryptophan (Trp) biosynthesis genes. It responds by transcription attenuation to two signals, Trp availability and inhibition of translation, and gives rise to two trans-acting products, the attenuator sRNA rnTrpL and the leader peptide peTrpL. In Escherichia coli, rnTrpL links Trp availability to initiation of chromosome replication and in Sinorhizobium meliloti, it coordinates regulation of split tryptophan biosynthesis operons. Furthermore, in S. meliloti, peTrpL is involved in mRNA destabilization in response to antibiotic exposure. It forms two types of asRNA-containing, antibiotic-dependent ribonucleoprotein complexes (ARNPs), one of them changing the target specificity of rnTrpL. The posttranscriptional role of peTrpL indicates two emerging paradigms: (1) sRNA reprograming by small molecules and (2) direct involvement of antibiotics in regulatory RNPs. They broaden our view on RNA-based mechanisms and may inspire new approaches for studying, detecting, and using antibacterial compounds. This article is categorized under: RNA Interactions with Proteins and Other Molecules > Small Molecule-RNA Interactions RNA Interactions with Proteins and Other Molecules > RNA-Protein Complexes Regulatory RNAs/RNAi/Riboswitches > Regulatory RNAs.
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Qiu X, Gao T, Yang J, Wang E, Liu L, Yuan H. Water-Soluble Humic Materials Modulating Metabolism and Triggering Stress Defense in Sinorhizobium fredii. Microbiol Spectr 2021; 9:e0029321. [PMID: 34479412 PMCID: PMC8552645 DOI: 10.1128/spectrum.00293-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2021] [Accepted: 07/29/2021] [Indexed: 11/23/2022] Open
Abstract
Bacteria have evolved a series of mechanisms to maintain their survival and reproduction in changeable and stressful environments. In-depth understanding of these mechanisms can allow for better developing and utilizing of bacteria with various biological functions. In this study, we found that water-soluble humic materials (WSHM), a well-known environment-friendly plant growth biostimulant, significantly promoted the free-living growth and survival of Sinorhizobium fredii CCBAU45436 in a bell-shaped, dose-dependent manner, along with more-efficient carbon source consumption and relief of medium acidification. By using RNA-Seq analysis, a total of 1,136 genes significantly up-/downregulated by external addition of WSHM were identified under test conditions. These differentially expressed genes (DEGs) were enriched in functional categories related to carbon/nitrogen metabolism, cellular stress response, and genetic information processing. Further protein-protein interaction (PPI) network analysis and reverse genetic engineering indicated that WSHM might reprogram the transcriptome through inhibiting the expression of key hub gene rsh, which encodes a bifunctional enzyme catalyzing synthesis and hydrolysis of the "magic spot" (p)ppGpp. In addition, the root colonization and viability in soil of S. fredii CCBAU45436 were increased by WSHM. These findings provide us with new insights into how WSHM benefit bacterial adaptations and demonstrate great application value to be a unique inoculant additive. IMPORTANCE Sinorhizobium fredii CCBAU45436 is a highly effective, fast-growing rhizobium that can establish symbiosis with multiple soybean cultivars. However, it is difficult to maintain the high-density effective viable cells in the rhizobial inoculant for the stressful conditions during production, storage, transport, and application. Here, we showed that WSHM greatly increased the viable cells of S. fredii CCBAU45436 in culture, modulating metabolism and triggering stress defense. The root colonization and viability in soil of S. fredii CCBAU45436 were also increased by WSHM. Our results shed new insights into the effects of WSHM on bacteria and the importance of metabolism and stress defense during the bacteria's whole life. In addition, the functional mechanism of WSHM may provide candidate genes for improving environmental adaptability and application potential of bacteria through genetic engineering.
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Affiliation(s)
- Xiaoqian Qiu
- State Key Laboratory of Agrobiotechnology and Key Laboratory of Soil Microbiology, Ministry of Agriculture, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Tongguo Gao
- College of Life Sciences, Hebei Agricultural University, Baoding, China
| | - Jinshui Yang
- State Key Laboratory of Agrobiotechnology and Key Laboratory of Soil Microbiology, Ministry of Agriculture, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Entao Wang
- Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Mexico City, Mexico
| | - Liang Liu
- State Key Laboratory of Agrobiotechnology and Key Laboratory of Soil Microbiology, Ministry of Agriculture, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Hongli Yuan
- State Key Laboratory of Agrobiotechnology and Key Laboratory of Soil Microbiology, Ministry of Agriculture, College of Biological Sciences, China Agricultural University, Beijing, China
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Capstaff NM, Morrison F, Cheema J, Brett P, Hill L, Muñoz-García JC, Khimyak YZ, Domoney C, Miller AJ. Fulvic acid increases forage legume growth inducing preferential up-regulation of nodulation and signalling-related genes. JOURNAL OF EXPERIMENTAL BOTANY 2020; 71:5689-5704. [PMID: 32599619 PMCID: PMC7501823 DOI: 10.1093/jxb/eraa283] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Accepted: 06/15/2020] [Indexed: 05/27/2023]
Abstract
The use of potential biostimulants is of broad interest in plant science for improving yields. The application of a humic derivative called fulvic acid (FA) may improve forage crop production. FA is an uncharacterized mixture of chemicals and, although it has been reported to increase growth parameters in many species including legumes, its mode of action remains unclear. Previous studies of the action of FA have lacked appropriate controls, and few have included field trials. Here we report yield increases due to FA application in three European Medicago sativa cultivars, in studies which include the appropriate nutritional controls which hitherto have not been used. No significant growth stimulation was seen after FA treatment in grass species in this study at the treatment rate tested. Direct application to bacteria increased Rhizobium growth and, in M. sativa trials, root nodulation was stimulated. RNA transcriptional analysis of FA-treated plants revealed up-regulation of many important early nodulation signalling genes after only 3 d. Experiments in plate, glasshouse, and field environments showed yield increases, providing substantial evidence for the use of FA to benefit M. sativa forage production.
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Affiliation(s)
- Nicola M Capstaff
- Department of Metabolic Biology, John Innes Centre, Norwich Research Park, Norwich, UK
| | - Freddie Morrison
- Department of Metabolic Biology, John Innes Centre, Norwich Research Park, Norwich, UK
| | - Jitender Cheema
- Department of Metabolic Biology, John Innes Centre, Norwich Research Park, Norwich, UK
| | - Paul Brett
- Department of Metabolic Biology, John Innes Centre, Norwich Research Park, Norwich, UK
| | - Lionel Hill
- Department of Metabolic Biology, John Innes Centre, Norwich Research Park, Norwich, UK
| | - Juan C Muñoz-García
- School of Pharmacy, University of East Anglia, Norwich Research Park, Norwich, UK
| | - Yaroslav Z Khimyak
- School of Pharmacy, University of East Anglia, Norwich Research Park, Norwich, UK
| | - Claire Domoney
- Department of Metabolic Biology, John Innes Centre, Norwich Research Park, Norwich, UK
| | - Anthony J Miller
- Department of Metabolic Biology, John Innes Centre, Norwich Research Park, Norwich, UK
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Melior H, Li S, Madhugiri R, Stötzel M, Azarderakhsh S, Barth-Weber S, Baumgardt K, Ziebuhr J, Evguenieva-Hackenberg E. Transcription attenuation-derived small RNA rnTrpL regulates tryptophan biosynthesis gene expression in trans. Nucleic Acids Res 2020; 47:6396-6410. [PMID: 30993322 PMCID: PMC6614838 DOI: 10.1093/nar/gkz274] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Revised: 03/01/2019] [Accepted: 04/12/2019] [Indexed: 01/06/2023] Open
Abstract
Ribosome-mediated transcription attenuation is a basic posttranscriptional regulation mechanism in bacteria. Liberated attenuator RNAs arising in this process are generally considered nonfunctional. In Sinorhizobium meliloti, the tryptophan (Trp) biosynthesis genes are organized into three operons, trpE(G), ppiD-trpDC-moaC-moeA, and trpFBA-accD-folC, of which only the first one, trpE(G), contains a short ORF (trpL) in the 5′-UTR and is regulated by transcription attenuation. Under conditions of Trp sufficiency, transcription is terminated between trpL and trpE(G), and a small attenuator RNA, rnTrpL, is produced. Here, we show that rnTrpL base-pairs with trpD and destabilizes the polycistronic trpDC mRNA, indicating rnTrpL-mediated downregulation of the trpDC operon in trans. Although all three trp operons are regulated in response to Trp availability, only in the two operons trpE(G) and trpDC the Trp-mediated regulation is controlled by rnTrpL. Together, our data show that the trp attenuator coordinates trpE(G) and trpDC expression posttranscriptionally by two fundamentally different mechanisms: ribosome-mediated transcription attenuation in cis and base-pairing in trans. Also, we present evidence that rnTrpL-mediated regulation of trpDC genes expression in trans is conserved in Agrobacterium and Bradyrhizobium, suggesting that the small attenuator RNAs may have additional conserved functions in the control of bacterial gene expression.
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Affiliation(s)
- Hendrik Melior
- Institute of Microbiology and Molecular Biology, Justus Liebig University, Giessen, 35392, Germany
| | - Siqi Li
- Institute of Microbiology and Molecular Biology, Justus Liebig University, Giessen, 35392, Germany
| | - Ramakanth Madhugiri
- Institute of Medical Virology, Justus Liebig University, Giessen, 35392, Germany
| | - Maximilian Stötzel
- Institute of Microbiology and Molecular Biology, Justus Liebig University, Giessen, 35392, Germany
| | - Saina Azarderakhsh
- Institute of Microbiology and Molecular Biology, Justus Liebig University, Giessen, 35392, Germany
| | - Susanne Barth-Weber
- Institute of Microbiology and Molecular Biology, Justus Liebig University, Giessen, 35392, Germany
| | - Kathrin Baumgardt
- Institute of Microbiology and Molecular Biology, Justus Liebig University, Giessen, 35392, Germany
| | - John Ziebuhr
- Institute of Medical Virology, Justus Liebig University, Giessen, 35392, Germany
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