A chloroplast-targeted cabbage DEAD-box RNA helicase BrRH22 confers abiotic stress tolerance to transgenic Arabidopsis plants by affecting translation of chloroplast transcripts

Genome-wide identification and analysis of DEAD-box RNA helicases in Gossypium hirsutum

DEAD-box RNA helicases, a prominent subfamily within the RNA helicase superfamily 2 (SF2), play crucial roles in the growth, development, and abiotic stress responses of plants. This study identifies 146 DEAD-box RNA helicase genes (GhDEADs) and categorizes them into four Clades (Clade A-D) through phylogenetic analysis. Promoter analysis reveals cis-acting elements linked to plant responses to light, methyl jasmonate (MeJA), abscisic acid (ABA), low temperature, and drought. RNA-seq data demonstrate that Clade C GhDEADs exhibit elevated and ubiquitous expression across different tissues, validating their connection to leaf development through real-time quantitative polymerase chain reaction (RT-qPCR) analysis. Notably, over half of GhDEADs display up-regulation in the leaves of virus-induced gene silencing (VIGS) plants of GhVIR-A/D (members of m6A methyltransferase complex, which regulate leaf morphogenesis). In conclusion, this study offers a comprehensive insight into GhDEADs, emphasizing their potential involvement in leaf development.

DEAD-Box RNA Helicase Family in Physic Nut (Jatropha curcas L.): Structural Characterization and Response to Salinity

Helicases, motor proteins present in both prokaryotes and eukaryotes, play a direct role in various steps of RNA metabolism. Specifically, SF2 RNA helicases, a subset of the DEAD-box family, are essential players in plant developmental processes and responses to biotic and abiotic stresses. Despite this, information on this family in the physic nut (Jatropha curcas L.) remains limited, spanning from structural patterns to stress responses. We identified 79 genes encoding DEAD-box RNA helicases (JcDHX) in the J. curcas genome. These genes were further categorized into three subfamilies: DEAD (42 genes), DEAH (30 genes), and DExH/D (seven genes). Characterization of the encoded proteins revealed a remarkable diversity, with observed patterns in domains, motifs, and exon-intron structures suggesting that the DEAH and DExH/D subfamilies in J. curcas likely contribute to the overall versatility of the family. Three-dimensional modeling of the candidates showed characteristic hallmarks, highlighting the expected functional performance of these enzymes. The promoter regions of the JcDHX genes revealed potential cis-elements such as Dof-type, BBR-BPC, and AP2-ERF, indicating their potential involvement in the response to abiotic stresses. Analysis of RNA-Seq data from the roots of physic nut accessions exposed to 150 mM of NaCl for 3 h showed most of the JcDHX candidates repressed. The protein-protein interaction network indicated that JcDHX proteins occupy central positions, connecting events associated with RNA metabolism. Quantitative PCR analysis validated the expression of nine DEAD-box RNA helicase transcripts, showing significant associations with key components of the stress response, including RNA turnover, ribosome biogenesis, DNA repair, clathrin-mediated vesicular transport, phosphatidyl 3,5-inositol synthesis, and mitochondrial translation. Furthermore, the induced expression of one transcript (JcDHX44) was confirmed, suggesting that it is a potential candidate for future functional analyses to better understand its role in salinity stress tolerance. This study represents the first global report on the DEAD-box family of RNA helicases in physic nuts and displays structural characteristics compatible with their functions, likely serving as a critical component of the plant's response pathways.

Unveiling unique alternative splicing responses to low temperature in Zoysia japonica through ZjRTD1.0, a high-quality reference transcript dataset

Inadequate reference databases in RNA-seq analysis can hinder data utilization and interpretation. In this study, we have successfully constructed a high-quality reference transcript dataset, ZjRTD1.0, for Zoysia japonica, a widely-used turfgrass with exceptional tolerance to various abiotic stress, including low temperatures and salinity. This dataset comprises 113,089 transcripts from 57,143 genes. BUSCO analysis demonstrates exceptional completeness (92.4%) in ZjRTD1.0, with reduced proportions of fragmented (3.3%) and missing (4.3%) orthologs compared to prior datasets. ZjRTD1.0 enables more precise analyses, including transcript quantification and alternative splicing assessments using public datasets, which identified a substantial number of differentially expressed transcripts (DETs) and differential alternative splicing (DAS) events, leading to several novel findings on Z. japonica's responses to abiotic stresses. First, spliceosome gene expression influenced alternative splicing significantly under abiotic stress, with a greater impact observed during low-temperature stress. Then, a significant positive correlation was found between the number of differentially expressed genes (DEGs) encoding protein kinases and the frequency of DAS events, suggesting the role of protein phosphorylation in regulating alternative splicing. Additionally, our results suggest possible involvement of serine/arginine-rich (SR) proteins and heterogeneous nuclear ribonucleoproteins (hnRNPs) in generating inclusion/exclusion isoforms under low-temperature stress. Furthermore, our investigation revealed a significantly enhanced overlap between DEGs and differentially alternatively spliced genes (DASGs) in response to low-temperature stress, suggesting a unique co-regulatory mechanism governing transcription and splicing in the context of low-temperature response. In conclusion, we have proven that ZjRTD1.0 will serve as a reliable and useful resource for future transcriptomic analyses in Z. japonica.

DEAD-box RNA helicase 6 regulates drought and abscisic acid stress responses in rapeseed (Brassica napus)

DEAD-box RNA helicase is a major subfamily of RNA helicases with vital roles played in plant growth, development, and plant-environment interactions. RNA helicase 6 in rapeseed (Brassica napus) (BnRH6) is a member of DEAD-box RNA helicase. While previous research has demonstrated the role of BnRH6 in salt stress regulation, the involvement of BnRH6 in drought stress adaptation remains unknown. This report described a function of BnRH6 in drought stress response. BnRH6 was sufficiently induced by osmotic stress. Transgenic Brassica napus and Arabidopsis thaliana (Arabidopsis) overexpressing BnRH6 (OE) showed a drought tolerance phenotype, characterized by improved plant growth, increased survival rates, reduced water loss, leaf chlorosis and oxidative stress. Furthermore, BnRH6 was also induced by exogenous abscisic acid (ABA). BnRH6 overexpression plants exhibited ABA hypersensitivity with lagging seed germination, growth stunt and diminished stomatal opening in the presence of ABA, suggesting the involvement of ABA signal. Assessment of several well-identified drought stress responsive genes such as Calcium-dependent Protein Kinase 14 (BnCDPK14), Enhanced Response to ABA1 (BnERA1) and ABA Insensitive 1 (BnABI1) revealed that their expressions were accordingly changed in BnOE plants, possibly with interplays between BnRH6 and those genes. Our data highlighted the functional role of BnRH6, which plays a positive role in active regulation of drought stress response likely through an ABA-dependent manner in rapeseed plants.

The Potyviral Protein 6K2 from Turnip Mosaic Virus Increases Plant Resilience to Drought

Virus infection can increase drought tolerance of infected plants compared with noninfected plants; however, the mechanisms mediating virus-induced drought tolerance remain unclear. In this study, we demonstrate turnip mosaic virus (TuMV) infection increases Arabidopsis thaliana survival under drought compared with uninfected plants. To determine if specific TuMV proteins mediate drought tolerance, we cloned the coding sequence for each of the major viral proteins and generated transgenic A. thaliana that constitutively express each protein. Three TuMV proteins, 6K1, 6K2, and NIa-Pro, enhanced drought tolerance of A. thaliana when expressed constitutively in plants compared with controls. While in the control plant, transcripts related to abscisic acid (ABA) biosynthesis and ABA levels were induced under drought, there were no changes in ABA or related transcripts in plants expressing 6K2 under drought compared with well-watered conditions. Expression of 6K2 also conveyed drought tolerance in another host plant, Nicotiana benthamiana, when expressed using a virus overexpression construct. In contrast to ABA, 6K2 expression enhanced salicylic acid (SA) accumulation in both Arabidopsis and N. benthamiana. These results suggest 6K2-induced drought tolerance is mediated through increased SA levels and SA-dependent induction of plant secondary metabolites, osmolytes, and antioxidants that convey drought tolerance. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Geographic isolation and environmental heterogeneity contribute to genetic differentiation in Cephalotaxus oliveri

Evaluating the contributions of geographic distance and environmental heterogeneity to the genetic divergence can inform the demographic history and responses to environmental change of natural populations. The isolation-by-distance (IBD) reveals that genetic differentiation among populations increases with geographic distance, while the isolation-by-environment (IBE) assumes a linear relationship between genetic variation and environmental differences among populations. Here, we sampled and genotyped 330 individuals from 18 natural populations of Cephalotaxus oliveri throughout the species' distribution. Twenty-eight EST-SSR markers were applied to analyze population genetics, for the investigation of the driving factors that shaped spatial structure. In addition, we identified the outlier loci under positive selection and tested their association with environmental factors. The results showed a moderate genetic diversity in C. oliveri and high genetic differentiation among populations. Population structure analyses indicated that 18 populations were clustered into two major groups. We observed that the genetic diversity of central populations decreased and the genetic differentiation increased towards the marginal populations. Additionally, the signatures of IBD and IBE were detected in C. oliveri, and IBE provided a better contribution to genetic differentiation. Six outlier loci under positive selection were demonstrated to be closely correlated with environmental variables, among which bio8 was associated with the greatest number of loci. Genetic evidence suggests the consistency of the central-marginal hypothesis (CMH) for C. oliveri. Furthermore, our results suggest that temperature-related variables played an important role in shaping genetic differentiation.

Identification of a DEAD-box RNA Helicase BnRH6 Reveals Its Involvement in Salt Stress Response in Rapeseed (Brassica napus)

Rapeseed (Brassica napus) is one of the most important vegetable oil crops worldwide. Abiotic stresses such as salinity are great challenges for its growth and productivity. DEAD-box RNA helicase 6 (RH6) is a subfamily member of superfamily 2 (SF2), which plays crucial roles in plant growth and development. However, no report is available on RH6 in regulating plant abiotic stress response. This study investigated the function and regulatory mechanism for BnRH6. BnRH6 was targeted to the nucleus and cytoplasmic processing body (P-body), constitutively expressed throughout the lifespan, and induced by salt stress. Transgenic overexpressing BnRH6 in Brassica and Arabidopsis displayed salt hypersensitivity, manifested by lagging seed germination (decreased to 55−85% of wild-type), growth stunt, leaf chlorosis, oxidative stress, and over-accumulation of Na ions with the K+/Na+ ratio being decreased by 18.3−28.6%. Given the undesirable quality of knockout Brassica plants, we utilized an Arabidopsis T-DNA insertion mutant rh6-1 to investigate downstream genes by transcriptomics. We constructed four libraries with three biological replicates to investigate global downstream genes by RNA sequencing. Genome-wide analysis of differentially expressed genes (DEGs) (2-fold, p < 0.05) showed that 41 genes were upregulated and 66 genes were downregulated in rh6-1 relative to wild-type under salt stress. Most of them are well-identified and involved in transcription factors, ABA-responsive genes, and detoxified components or antioxidants. Our research suggests that BnRH6 can regulate a group of salt-tolerance genes to negatively promote Brassica adaptation to salt stress.

Gene Networks Involved in Plant Heat Stress Response and Tolerance

Global warming is an environmental problem that cannot be ignored. High temperatures seriously affect the normal growth and development of plants, and threaten the development of agriculture and the distribution and survival of species at risk. Plants have evolved complex but efficient mechanisms for sensing and responding to high temperatures, which involve the activation of numerous functional proteins, regulatory proteins, and non-coding RNAs. These mechanisms consist of large regulatory networks that regulate protein and RNA structure and stability, induce Ca²⁺ and hormone signal transduction, mediate sucrose and water transport, activate antioxidant defense, and maintain other normal metabolic pathways. This article reviews recent research results on the molecular mechanisms of plant response to high temperatures, highlighting future directions or strategies for promoting plant heat tolerance, thereby helping to identify the regulatory mechanisms of heat stress responses in plants.

RNA-Binding Proteins: The Key Modulator in Stress Granule Formation and Abiotic Stress Response

To cope with abiotic environmental stress, plants rapidly change their gene expression transcriptionally and post-transcriptionally, the latter by translational suppression of selected proteins and the assembly of cytoplasmic stress granules (SGs) that sequester mRNA transcripts. RNA-binding proteins (RBPs) are the major players in these post-transcriptional processes, which control RNA processing in the nucleus, their export from the nucleus, and overall RNA metabolism in the cytoplasm. Because of their diverse modular domain structures, various RBP types dynamically co-assemble with their targeted RNAs and interacting proteins to form SGs, a process that finely regulates stress-responsive gene expression. This review summarizes recent findings on the involvement of RBPs in adapting plants to various abiotic stresses via modulation of specific gene expression events and SG formation. The relationship of these processes with the stress hormone abscisic acid (ABA) is discussed.

Function of Chloroplasts in Plant Stress Responses

The chloroplast has a central position in oxygenic photosynthesis and primary metabolism. In addition to these functions, the chloroplast has recently emerged as a pivotal regulator of plant responses to abiotic and biotic stress conditions. Chloroplasts have their own independent genomes and gene-expression machinery and synthesize phytohormones and a diverse range of secondary metabolites, a significant portion of which contribute the plant response to adverse conditions. Furthermore, chloroplasts communicate with the nucleus through retrograde signaling, for instance, reactive oxygen signaling. All of the above facilitate the chloroplast’s exquisite flexibility in responding to environmental stresses. In this review, we summarize recent findings on the involvement of chloroplasts in plant regulatory responses to various abiotic and biotic stresses including heat, chilling, salinity, drought, high light environmental stress conditions, and pathogen invasions. This review will enrich the better understanding of interactions between chloroplast and environmental stresses, and will lay the foundation for genetically enhancing plant-stress acclimatization.

Alpha-ketoglutarate-dependent dioxygenase homolog 10B, an N6 -methyladenosine mRNA demethylase, plays a role in salt stress and abscisic acid responses in Arabidopsis thaliana

N⁶ -methyladenosine (m⁶ A) is an abundant methylation mark in eukaryotic mRNAs. It is installed and removed by methyltransferases ("writers") and demethylases ("erasers"), respectively. A recent study has demonstrated that alpha-ketoglutarate-dependent dioxygenase homolog 10B (ALKBH10B) is an mRNA m⁶ A eraser affecting floral transition in Arabidopsis thaliana. However, the roles of m⁶ A eraser proteins, including ALKHB10B, in plant adaptation to abiotic stresses are largely unknown. In this study, we aimed to determine the role of ALKBH10B in the response of A. thaliana to abiotic stresses and abscisic acid (ABA). The m⁶ A level increased in response to salt stress, and m⁶ A levels in alkbh10b mutants were higher than those in the wild-type under both normal and salt stress conditions. Germination of alkbh10b mutant seeds was markedly delayed under salt stress but not under dehydration, cold, or ABA conditions. Seedling growth and survival rate of alkbh10b mutants were enhanced under salt stress. Notably, salt-tolerant phenotypes of alkbh10b mutants were correlated with decreased levels of several m⁶ A-modified genes, including ATAF1, BGLU22, and MYB73, which are negative effectors of salt stress tolerance. In response to ABA, both seedling and root growth of alkbh10b mutants were inhibited via upregulating ABA signaling-related genes, including ABI3 and ABI4. Collectively, these findings indicate that ALKBH10B-mediated m⁶ A demethylation affects the transcript levels of stress-responsive genes, which are important for seed germination, seedling growth, and survival of Arabidopsis thaliana in response to salt stress or ABA.

The temperature-regulated DEAD-box RNA helicase CrhR interactome: Autoregulation and photosynthesis-related transcripts

RNA helicases play crucial functions in RNA biology. In plants, RNA helicases are encoded by large gene families, performing roles in abiotic stress responses, development, the post-transcriptional regulation of gene expression as well as house-keeping functions. Several of these RNA helicases are targeted to the organelles, mitochondria and chloroplasts. Cyanobacteria are the direct evolutionary ancestors of plant chloroplasts. The cyanobacterium Synechocystis 6803 encodes a single DEAD-box RNA helicase, CrhR, that is induced by a range of abiotic stresses, including low temperature. Though the ΔcrhR mutant exhibits a severe cold-sensitive phenotype, the physiological function(s) performed by CrhR have not been described. To identify transcripts interacting with CrhR, we performed RNA co-immunoprecipitation with extracts from a Synechocystis crhR deletion mutant expressing the FLAG-tagged native CrhR or a K57A mutated version with an anticipated enhanced RNA binding. The composition of the interactome was strikingly biased towards photosynthesis-associated and redox-controlled transcripts. A transcript highly enriched in all experiments was the crhR mRNA, suggesting an auto-regulatory molecular mechanism. The identified interactome explains the described physiological role of CrhR in response to the redox poise of the photosynthetic electron transport chain and characterizes CrhR as an enzyme with a diverse range of transcripts as molecular targets.

The Role of Chloroplast Gene Expression in Plant Responses to Environmental Stress

Chloroplasts are plant organelles that carry out photosynthesis, produce various metabolites, and sense changes in the external environment. Given their endosymbiotic origin, chloroplasts have retained independent genomes and gene-expression machinery. Most genes from the prokaryotic ancestors of chloroplasts were transferred into the nucleus over the course of evolution. However, the importance of chloroplast gene expression in environmental stress responses have recently become more apparent. Here, we discuss the emerging roles of the distinct chloroplast gene expression processes in plant responses to environmental stresses. For example, the transcription and translation of psbA play an important role in high-light stress responses. A better understanding of the connection between chloroplast gene expression and environmental stress responses is crucial for breeding stress-tolerant crops better able to cope with the rapidly changing environment.

The res (restored cell structure by salinity) tomato mutant reveals the role of the DEAD-box RNA helicase SlDEAD39 in plant development and salt response

Increasing evidences highlight the importance of DEAD-box RNA helicases in plant development and stress responses. In a previous study, we characterized the tomato res mutant (restored cell structure by salinity), showing chlorosis and development alterations that reverted under salt-stress conditions. Map-based cloning demonstrates that RES gene encodes SlDEAD39, a chloroplast-targeted DEAD-box RNA helicase. Constitutive expression of SlDEAD39 complements the res mutation, while the silencing lines had a similar phenotype than res mutant, which is also reverted under salinity. Functional analysis of res mutant proved SlDEAD39 is involved in the in vivo processing of the chloroplast, 23S rRNA, at the hidden break-B site, a feature also supported by in vitro binding experiments of the protein. In addition, our results show that other genes coding for chloroplast-targeted DEAD-box proteins are induced by salt-stress, which might explain the rescue of the res mutant phenotype. Interestingly, salinity restored the phenotype of res adult plants by increasing their sugar content and fruit yield. Together, these results propose an unprecedented role of a DEAD-box RNA helicase in regulating plant development and stress response through the proper ribosome and chloroplast functioning, which, in turn, represents a potential target to improve salt tolerance in tomato crops.

Roles of Organellar RNA-Binding Proteins in Plant Growth, Development, and Abiotic Stress Responses

Organellar gene expression (OGE) in chloroplasts and mitochondria is primarily modulated at post-transcriptional levels, including RNA processing, intron splicing, RNA stability, editing, and translational control. Nucleus-encoded Chloroplast or Mitochondrial RNA-Binding Proteins (nCMRBPs) are key regulatory factors that are crucial for the fine-tuned regulation of post-transcriptional RNA metabolism in organelles. Although the functional roles of nCMRBPs have been studied in plants, their cellular and physiological functions remain largely unknown. Nevertheless, existing studies that have characterized the functions of nCMRBP families, such as chloroplast ribosome maturation and splicing domain (CRM) proteins, pentatricopeptide repeat (PPR) proteins, DEAD-Box RNA helicase (DBRH) proteins, and S1-domain containing proteins (SDPs), have begun to shed light on the role of nCMRBPs in plant growth, development, and stress responses. Here, we review the latest research developments regarding the functional roles of organellar RBPs in RNA metabolism during growth, development, and abiotic stress responses in plants.

Comparative Analysis of two Sugarcane Ancestors Saccharum officinarum and S. spontaneum based on Complete Chloroplast Genome Sequences and Photosynthetic Ability in Cold Stress

Polyploid Saccharum with complex genomes hindered the progress of sugarcane improvement, while their chloroplast genomes are much smaller and simpler. Chloroplast (cp), the vital organelle, is the site of plant photosynthesis, which also evolves other functions, such as tolerance to environmental stresses. In this study, the cp genome of two sugarcane ancestors Saccharum officinarum and S. spontaneum were sequenced, and genome comparative analysis between these two species was carried out, together with the photosynthetic ability. The length is 141,187 bp for S. officinarum and that is 7 bp longer than S. spontaneum, with the same GC content (38.44%) and annotated gene number (134), 13 with introns among them. There is a typical tetrad structure, including LSC, SSC, IRb and IRa. Of them, LSC and IRa/IRb are 18 bp longer and 6 bp shorter than those in S. spontaneum (83,047 bp and 22,795 bp), respectively, while the size of SSC is same (12,544 bp). Five genes exhibit contraction and expansion at the IR junctions, but only one gene ndhF with 29 bp expansion at the border of IRb/SSC. Nucleotide diversity (Pi) based on sliding window analysis showed that the single copy and noncoding regions were more divergent than IR- and coding regions, and the variant hotspots trnG-trnM, psbM-petN, trnR-rps14, ndhC-trnV and petA-psbJ in the LSC and trnL-ccsA in the SSC regions were detected, and petA-psbJ with the highest divergent value of 0.01500. Genetic distances of 65 protein genes vary from 0.00000 to 0.00288 between two species, and the selective pressure on them indicated that only petB was subjected to positive selection, while more genes including rpoC2, rps3, ccsA, ndhA, ndhA, psbI, atpH and psaC were subjected to purifying or very strong purifying selection. There are larger number of codons in S. spontaneum than that in S. officinarum, while both species have obvious codon preference and the codons with highest-(AUG) and lowest frequency (AUA) are same. Whilst, the most abundant amino acid is leucine in both S. officinarum and S. spontaneum, with number of 2175 (10.88% of total) and 2228 (10.90% of total) codons, respectively, and the lowest number is cysteine, with only 221 (1.105%) and 224 (1.096%), respectively. Protein collinearity analysis showed the high collinearity though several divergences were present in cp genomes, and identification of simple sequence repeats (SSRs) were included in this study. In addition, in order to compare cold tolerance and explore the expanding function of this environmental stress, the chlorophyll relative content (SPAD) and chlorophyll fluorescence Fv/Fm were measured. The significantly higher SPAD were observed in S. spontaneum than those in S. officinarum, no matter what the control conditions, exposure to low temperature or during recovery, and so was for Fv/Fm under exposure to low temperature, together with higher level of SPAD in S. spontaneum in each measurement. Aforementioned results suggest much stronger photosynthetic ability and cold tolerance in S. spontaneum. Our findings build a foundation to investigate the biological mechanism of two sugarcane ancestor chloroplasts and retrieve reliable molecular resources for phylogenetic and evolutionary studies, and will be conducive to genetic improvement of photosynthetic ability and cold resistance in modern sugarcane.

Transcriptional and Post-transcriptional Regulation of Organellar Gene Expression (OGE) and Its Roles in Plant Salt Tolerance

Given their endosymbiotic origin, chloroplasts and mitochondria genomes harbor only between 100 and 200 genes that encode the proteins involved in organellar gene expression (OGE), photosynthesis, and the electron transport chain. However, as the activity of these organelles also needs a few thousand proteins encoded by the nuclear genome, a close coordination of the gene expression between the nucleus and organelles must exist. In line with this, OGE regulation is crucial for plant growth and development, and is achieved mainly through post-transcriptional mechanisms performed by nuclear genes. In this way, the nucleus controls the activity of organelles and these, in turn, transmit information about their functional state to the nucleus by modulating nuclear expression according to the organelles' physiological requirements. This adjusts organelle function to plant physiological, developmental, or growth demands. Therefore, OGE must appropriately respond to both the endogenous signals and exogenous environmental cues that can jeopardize plant survival. As sessile organisms, plants have to respond to adverse conditions to acclimate and adapt to them. Salinity is a major abiotic stress that negatively affects plant development and growth, disrupts chloroplast and mitochondria function, and leads to reduced yields. Information on the effects that the disturbance of the OGE function has on plant tolerance to salinity is still quite fragmented. Nonetheless, many plant mutants which display altered responses to salinity have been characterized in recent years, and interestingly, several are affected in nuclear genes encoding organelle-localized proteins that regulate the expression of organelle genes. These results strongly support a link between OGE and plant salt tolerance, likely through retrograde signaling. Our review analyzes recent findings on the OGE functions required by plants to respond and tolerate salinity, and highlights the fundamental role that chloroplast and mitochondrion homeostasis plays in plant adaptation to salt stress.

Rice OsRH58, a chloroplast DEAD-box RNA helicase, improves salt or drought stress tolerance in Arabidopsis by affecting chloroplast translation

BACKGROUND

Despite increasing characterization of DEAD-box RNA helicases (RHs) in chloroplast gene expression regulation at posttranscriptional levels in plants, their functional roles in growth responses of crops, including rice (Oryza sativa), to abiotic stresses are yet to be characterized. In this study, rice OsRH58 (LOC_Os01g73900), a chloroplast-localized DEAD-box RH, was characterized for its expression patterns upon stress treatment and its functional roles using transgenic Arabidopsis plants under normal and abiotic stress conditions.

RESULTS

Chloroplast localization of OsRH58 was confirmed by analyzing the expression of OsRH58-GFP fusion proteins in tobacco leaves. Expression of OsRH58 in rice was up-regulated by salt, drought, or heat stress, whereas its expression was decreased by cold, UV, or ABA treatment. The OsRH58-expressing Arabidopsis plants were taller and had more seeds than the wild type under favorable conditions. The transgenic plants displayed faster seed germination, better seedling growth, and a higher survival rate than the wild type under high salt or drought stress. Importantly, levels of several chloroplast proteins were increased in the transgenic plants under salt or dehydration stress. Notably, OsRH58 harbored RNA chaperone activity.

CONCLUSIONS

These findings suggest that the chloroplast-transported OsRH58 possessing RNA chaperone activity confers stress tolerance by increasing translation of chloroplast mRNAs.