Role of plant RNA-binding proteins in development, stress response and genome organization

Ribosome stalling-induced NIP5;1 mRNA decay triggers ARGONAUTE1-dependent transcription downregulation

In eukaryotes, messenger RNA (mRNA) accumulation is regulated through the levels of transcription, processing, and degradation. Here, we uncover the multi-level regulatory mechanism governing the expression of NIP5;1, a boron (B) diffusion facilitator in Arabidopsis. B-dependent NIP5;1 mRNA degradation is triggered by ribosome stalling at an AUGUAA sequence in its 5'-untranslated region. We showed that deletion of ATGTAA also abolishes B-dependent transcriptional downregulation, revealing a dual role of this sequence in both mRNA degradation and transcriptional control. Small RNAs (sRNAs) and ARGONAUTE1 (AGO1) are implicated in mRNA-degradation-mediated B-dependent transcriptional downregulation: a 5'-3' exonuclease mutant, xrn4, presents both elevated levels of NIP5;1 mRNA degradation intermediates and transcriptional downregulation; AGO1-associated sRNA-sequencing reveals the presence of sRNAs with sequences upstream of NIP5;1 AUGUAA; and nascent mRNA profiling by global run-on sequencing demonstrates RNA polymerase II pausing at ATGTAA, a phenomenon diminished in the ago1 mutant that lacks B-dependent transcriptional downregulation. These findings point to multi-level coordination of NIP5;1 expression with the AUGUAA sequence at its core: ribosome stalling orchestrates translational inhibition, mRNA degradation and transcriptional downregulation in response to B. The fast response resulting from this synergy suggests that similar mechanisms may exist in other eukaryotic systems for efficient and rapid regulation of gene expression.

Genome-wide identification and analysis of the UBA2 gene family in wheat (Triticum aestivum L.)

BACKGROUND

RNA-binding proteins (RBPs) participate in multiple aspects of RNA metabolism, which in turn regulates gene expression, thereby involving in organism growth and development. The UBA2 family, one of the subfamilies of RBPs, has been identified in several plant species. However, few researches have been performed to investigate the role of UBA2 in wheat (Triticum aestivum).

RESULTS

In this study, we identified eleven TaUBA2s and divided them into three groups according to their domain characteristics. Phylogenetic analysis was conducted to forecast functional similarities among Arabidopsis, rice, maize and wheat UBA2 genes. Members within the same subfamily of TaUBA2 are relatively conserved in terms of protein structure, motifs, and gene structure. Chromosomal location and synteny analysis suggested that the segmental duplication events played important roles during TaUBA2s evolution. The cis-acting element analysis showed that TaUBA2s were involved in hormone response, development, light response, metabolism, and response to environmental stress. Furthermore, TaUBA2C contains two RNA recognition motifs (RRMs), and the first RRM is responsible for the nuclear speckle formation of TaUBA2C, whereas the two RRMs are necessary for its biological function.

CONCLUSIONS

Taken together, our study provides a comprehensive analysis of the TaUBA2 family in wheat and lays the foundation for the future functional investigations of TaUBA2s in wheat growth, development and stress responses.

Enhanced HSP70 binding to m6A-methylated RNAs facilitates cold stress adaptation in mango seedlings

BACKGROUND

Cold stress poses a serious challenge to tropical fruit production, particularly in mango. N6-methyladenosine (m6A) modifications are key regulators of gene expression, enabling plants to respond to stress responses, enhance adaptation and improve resilience to environmental challenges.

RESULTS

In our study, transcriptome-wide m6A methylation profiling under cold stress identified 6,499 differentially methylated m6A peaks and 2,164 differentially expressed genes (DEGs) in mango seedlings. Among these genes, six exhibited both significant increases in m6A modification levels and gene expression, 21 showed a significant increase in m6A levels but a concurrent downregulation of gene expression, and 26 showed reduced m6A levels but exhibited increased gene expression, highlighting distinct regulatory patterns in m6A-mediated gene expression control. Gene Ontology (GO) enrichment analysis revealed significant involvement in pathways such as potassium ion import, nitrate response, and transcription regulation. Notably, HSP70 was one of the upregulated genes in response to cold stress. RNA immunoprecipitation (RNA-IP) assays confirmed the association of HSP70 with m6A-modified RNAs in vivo, supporting its role in regulating stress-responsive transcripts. Additionally, immunofluorescence analysis demonstrated the formation of HSP70 condensates in plant cells under cold stress, indicating a potential mechanism for localized RNA stabilization. Fluorescence polarization assays demonstrated that HSP70 binds preferentially to m6A-modified RNAs, suggesting its role in forming protective condensates under cold conditions. This interaction between m6A modification and HSP70 points to a potential mechanism that helps stabilize stress-responsive transcripts, contributing to the plant's enhanced cold tolerance.

CONCLUSIONS

m6A modifications play a vital role in regulating gene expression under cold stress, offering new insights into mango's stress responses and potential breeding strategies for cold tolerance.

Structural insights to the RRM-domain of the glycine-rich RNA-binding protein from Sorghum bicolor and its role in cold stress tolerance in E. coli

Sorghum bicolor Glycine-rich RNA-binding protein (SbGRBP), exhibit the ability to bind both single-stranded and double-stranded DNA. The expression of SbGRBP is regulated by heat stress, with the protein localizing to the nucleus and cytosol. The present study delves into the structure and ssDNA binding ability of its truncated version (SbGRBP1-119) which lacks glycine rich domain (GR). This protein has the ability to bind ssDNA Using Nuclear Magnetic Resonance (NMR) spectroscopy, we have revealed the secondary structure of SbGRBP1-119, highlighting the typical configuration of GRBPs with four β-sheets and two α-helices. Notably, we found two additional α-helices at the N-terminal region that seem to interact with ssDNA, a novel observation for GRBPs. Key residues crucial for ssDNA binding were identified, suggesting a specific interaction with the oligonucleotide sequence 5'-TTCTGG-3'. Preliminary assays hinted that SbGRBP1-119 might bolster E. coli resilience to cold stress, indicating a potential chaperone-like role under stress conditions. This study sheds light on the structural basis of SbGRBP1-119's interaction with nucleic acids, deepening our understanding about the role of GRBPs' in RNA metabolism and regulation.

Identification of the RRM1 gene family in rice (Oryza sativa) and its response to rice blast

To better understand RNA-binding proteins in rice, a comprehensive investigation was conducted on the RRM1 gene family of rice. It encompassed genome-wide identification and exploration of its role in rice blast resistance. The physicochemical properties of the rice OsRRM1 gene family were analyzed. There genes were also analyzed for their conserved domains, motifs, location information, gene structure, phylogenetic trees, collinearity, and cis-acting elements. Furthermore, alterations in the expression patterns of selected OsRRM1 genes were assessed using quantitative real-time PCR (qRT-PCR). A total of 212 members of the OsRRM1 gene family were identified, which were dispersed across 12 chromosomes. These genes all exhibit multiple exons and introns, all of which encompass the conserved RRM1 domain and share analogous motifs. This observation suggests a high degree of conservation within the encoded sequence domain of these genes. Phylogenetic analysis revealed the existence of five subfamilies within the OsRRM1 gene family. Furthermore, investigation of the promoter region identified cis-regulatory elements that are involved in nucleic acid binding and interaction with multiple transcription factors. By employing GO and KEGG analyses, four RRM1 genes were tentatively identified as crucial contributors to plant immunity, while the RRM1 gene family was also found to have a significant involvement in the complex of alternative splicing. The qRT-PCR results revealed distinct temporal changes in the expression patterns of OsRRM1 genes following rice blast infection. Additionally, gene expression analysis indicates that the majority of OsRRM1 genes exhibited constitutive expressions. These findings enrich our understanding of the OsRRM1 gene family. They also provide a foundation for further research on immune mechanisms rice and the management of rice blast.

A commitment for life: Decades of unraveling the molecular mechanisms behind seed dormancy and germination

Seeds are unique time capsules that can switch between 2 complex and highly interlinked stages: seed dormancy and germination. Dormancy contributes to the survival of plants because it allows to delay germination to optimal conditions. The switch between dormancy and germination occurs in response to developmental and environmental cues. In this review we provide a comprehensive overview of studies that have helped to unravel the molecular mechanisms underlying dormancy and germination over the last decades. Genetic and physiological studies provided a strong foundation for this field of research and revealed the critical role of the plant hormones abscisic acid and gibberellins in the regulation of dormancy and germination, and later natural variation studies together with quantitative genetics identified previously unknown genetic components that control these processes. Omics technologies like transcriptome, proteome, and translatomics analysis allowed us to mechanistically dissect these processes and identify new components in the regulation of seed dormancy and germination.

Divergence in regulatory mechanisms of GR-RBP genes in different plants under abiotic stress

The IVa subfamily of glycine-rich proteins (GRPs) comprises a group of glycine-rich RNA binding proteins referred to as GR-RBPa here. Previous studies have demonstrated functions of GR-RBPa proteins in regulating stress response in plants. However, the mechanisms responsible for the differential regulatory functions of GR-RBPa proteins in different plant species have not been fully elucidated. In this study, we identified and comprehensively studied a total of 34 GR-RBPa proteins from five plant species. Our analysis revealed that GR-RBPa proteins were further classified into two branches, with proteins in branch I being relatively more conserved than those in branch II. When subjected to identical stresses, these genes exhibited intensive and differential expression regulation in different plant species, corresponding to the enrichment of cis-acting regulatory elements involving in environmental and internal signaling in these genes. Unexpectedly, all GR-RBPa genes in branch I underwent intensive alternative splicing (AS) regulation, while almost all genes in branch II were only constitutively spliced, despite having more introns. This study highlights the complex and divergent regulations of a group of conserved RNA binding proteins in different plants when exposed to identical stress conditions. These species-specific regulations may have implications for stress responses and adaptations in different plant species.

Integrated transcriptome and proteome analysis provides insights into CpFPA1 for floral induction in Chimonanthus praecox (Magnoliidae) without FLC in genome

KEY MESSAGE

We used transcriptomic and proteomic association analysis to reveal the critical genes/proteins at three key flower bud differentiation stages and overexpression of CpFPA1 in Arabidopsis resulted in earlier flowering. Wintersweet (Chimonanthus praecox), a rare winter-flowering woody plant, is well known for its unique blooming time, fragrance and long flowering period. However, the molecular mechanism of flowering in C. praecox remains poorly unclear. In this study, we used transcriptomic and proteomic association analysis to reveal the critical genes/proteins at three key flower bud (FB) differentiation stages (FB.Apr, FB.May and FB.Nov) in C. praecox. The results showed that a total of 952 differential expressed genes (DEGs) and 40 differential expressed proteins (DEPs) were identified. Gene ontology (GO) enrichment revealed that DEGs in FB.Apr/FB.May comparison group were mainly involved in metabolic of biological process, cell and cell part of cellular component and catalytic activity of molecular function. In the EuKaryotic Orthologous Groups (KOG) functional classification, DEPs were predicted mainly in the function of general function prediction only (KOG0118), post-translational modification, protein turnover and chaperones. The autonomous pathway genes play an essential role in the floral induction. Based on transcriptome and proteome correlation analysis, six candidate genes associated with the autonomous pathway were identified, including FPA1, FPA2a, FPA2b, FCA, FLK, FY. Furthermore, CpFPA1 was isolated and functionally characterized, and ectopic expression of CpFPA1 in Arabidopsis Columbia (Col-0) resulted in earlier flowering. These data could contribute to understand the function of CpFPA1 for floral induction and provide information for further research on the molecular mechanisms of flowering in wintersweet.

DGW1, encoding an hnRNP-like RNA binding protein, positively regulates grain size and weight by interacting with GW6 mRNA

Grain size and weight determine rice yield. Although numerous genes and pathways involved in regulating grain size have been identified, our knowledge of post-transcriptional control of grain size remains elusive. In this study, we characterize a rice mutant, decreased grain width and weight 1 (dgw1), which produces small grains. We show that DGW1 encodes a member of the heterogeneous nuclear ribonucleoprotein (hnRNP) family protein and preferentially expresses in developing panicles, positively regulating grain size by promoting cell expansion in spikelet hulls. Overexpression of DGW1 increases grain weight and grain numbers, leading to a significant rise in rice grain yield. We further demonstrate that DGW1 functions in grain size regulation by directly binding to the mRNA of Grain Width 6 (GW6), a critical grain size regulator in rice. Overexpression of GW6 restored the grain size phenotype of DGW1-knockout plants. DGW1 interacts with two oligouridylate binding proteins (OsUBP1a and OsUBP1b), which also bind the GW6 mRNA. In addition, the second RRM domain of DGW1 is indispensable for its mediated protein-RNA and protein-protein interactions. In summary, our findings identify a new regulatory module of DGW1-GW6 that regulates rice grain size and weight, providing important insights into the function of hnRNP-like proteins in the regulation of grain size.

Post-transcriptional regulation of grain weight and shape by the RBP-A-J-K complex in rice

RNA-binding proteins (RBPs) are components of the post-transcriptional regulatory system, but their regulatory effects on complex traits remain unknown. Using an integrated strategy involving map-based cloning, functional characterizations, and transcriptomic and population genomic analyses, we revealed that RBP-K (LOC_Os08g23120), RBP-A (LOC_Os11g41890), and RBP-J (LOC_Os10g33230) encode proteins that form an RBP-A-J-K complex that negatively regulates rice yield-related traits. Examinations of the RBP-A-J-K complex indicated RBP-K functions as a relatively non-specific RBP chaperone that enables RBP-A and RBP-J to function normally. Additionally, RBP-J most likely affects GA pathways, resulting in considerable increases in grain and panicle lengths, but decreases in grain width and thickness. In contrast, RBP-A negatively regulates the expression of genes most likely involved in auxin-regulated pathways controlling cell wall elongation and carbohydrate transport, with substantial effects on the rice grain filling process as well as grain length and weight. Evolutionarily, RBP-K is relatively ancient and highly conserved, whereas RBP-J and RBP-A are more diverse. Thus, the RBP-A-J-K complex may represent a typical functional model for many RBPs and protein complexes that function at transcriptional and post-transcriptional levels in plants and animals for increased functional consistency, efficiency, and versatility, as well as increased evolutionary potential. Our results clearly demonstrate the importance of RBP-mediated post-transcriptional regulation for the diversity of complex traits. Furthermore, rice grain yield and quality may be enhanced by introducing various complete or partial loss-of-function mutations to specific RBP genes using clustered regularly interspaced palindromic repeats (CRISPR)/CRISPR-associated protein 9 technology and by exploiting desirable natural tri-genic allelic combinations at the loci encoding the components of the RBP-A-J-K complex through marker-assisted selection.

The Glycine-Rich RNA-Binding Protein Is a Vital Post-Transcriptional Regulator in Crops

Glycine-rich RNA binding proteins (GR-RBPs), a branch of RNA binding proteins (RBPs), play integral roles in regulating various aspects of RNA metabolism regulation, such as RNA processing, transport, localization, translation, and stability, and ultimately regulate gene expression and cell fate. However, our current understanding of GR-RBPs has predominantly been centered on Arabidopsis thaliana, a model plant for investigating plant growth and development. Nonetheless, an increasing body of literature has emerged in recent years, shedding light on the presence and functions of GRPs in diverse crop species. In this review, we not only delineate the distinctive structural domains of plant GR-RBPs but also elucidate several contemporary mechanisms of GR-RBPs in the post-transcriptional regulation of RNA. These mechanisms encompass intricate processes, including RNA alternative splicing, polyadenylation, miRNA biogenesis, phase separation, and RNA translation. Furthermore, we offer an exhaustive synthesis of the diverse roles that GR-RBPs fulfill within crop plants. Our overarching objective is to provide researchers and practitioners in the field of agricultural genetics with valuable insights that may inform and guide the application of plant genetic engineering for enhanced crop development and sustainable agriculture.

Plants use molecular mechanisms mediated by biomolecular condensates to integrate environmental cues with development

This review highlights recent literature on biomolecular condensates in plant development and discusses challenges for fully dissecting their functional roles. Plant developmental biology has been inundated with descriptive examples of biomolecular condensate formation, but it is only recently that mechanistic understanding has been forthcoming. Here, we discuss recent examples of potential roles biomolecular condensates play at different stages of the plant life cycle. We group these examples based on putative molecular functions, including sequestering interacting components, enhancing dwell time, and interacting with cytoplasmic biophysical properties in response to environmental change. We explore how these mechanisms could modulate plant development in response to environmental inputs and discuss challenges and opportunities for further research into deciphering molecular mechanisms to better understand the diverse roles that biomolecular condensates exert on life.

Toward a systems view on RNA-binding proteins and associated RNAs in plants: Guilt by association

RNA-binding proteins (RBPs) have a broad impact on most biochemical, physiological, and developmental processes in a plant's life. RBPs engage in an on-off relationship with their RNA partners, accompanying virtually every stage in RNA processing and function. While the function of a plethora of RBPs in plant development and stress responses has been described, we are lacking a systems-level understanding of components in RNA-based regulation. Novel techniques have substantially enlarged the compendium of proteins with experimental evidence for binding to RNAs in the cell, the RNA-binding proteome. Furthermore, ribonomics methods have been adapted for use in plants to profile the in vivo binding repertoire of RBPs genome-wide. Here, we discuss how recent technological achievements have provided novel insights into the mode of action of plant RBPs at a genome-wide scale. Furthermore, we touch upon two emerging topics, the connection of RBPs to phase separation in the cell and to extracellular RNAs. Finally, we define open questions to be addressed to move toward an integrated understanding of RBP function.

ECT9 condensates with ECT1 and regulates plant immunity

Mounting an efficient defense against pathogens requires RNA binding proteins (RBPs) to regulate immune mRNAs transcription, splicing, export, translation, storage, and degradation. RBPs often have multiple family members, raising the question of how they coordinate to carry out diverse cellular functions. In this study, we demonstrate that EVOLUTIONARILY CONSERVED C-TERMINAL REGION 9 (ECT9), a member of the YTH protein family in Arabidopsis, can condensate with its homolog ECT1 to control immune responses. Among the 13 YTH family members screened, only ECT9 can form condensates that decrease after salicylic acid (SA) treatment. While ECT1 alone cannot form condensates, it can be recruited to ECT9 condensates in vivo and in vitro. Notably, the ect1/9 double mutant, but not the single mutant, exhibits heightened immune responses to the avirulent pathogen. Our findings suggest that co-condensation is a mechanism by which RBP family members confer redundant functions.

AtSIEK, an EXD1-like protein with KH domain, involves in salt stress response by interacting with FRY2/CPL1

Abiotic stress has great impacts on plant germination, growth and development and crop yield. Therefore, it is important to understand the molecular mechanism of plants response to abiotic stress. In this study, we identified a plant specific protein AtSIEK (stress-induced protein with EXD1-like domain and KH domain) response to salt stress. AtSIEK encodes a hnRNP K homology (KH) protein localized in nucleus. Amino acid sequences analysis found that SIEK protein is specific in plants, containing two domains with EXD1-like domain and KH domain, while SIEK homolog in animals only had EXD1-like domain without KH domain. Physiology experiments revealed that AtSIEK was significantly induced under salt stress and the siek mutant shows sensitive to salt stress, indicating that AtSIEK was a positive regulator in stress response. Further, molecular, biochemical, and genetic assays suggested that AtSIEK interacts with FRY2/CPL1, a known regulator in response to abiotic stress, and they function synergistically in response to salt stress. Taken together, these results shed new light on the regulation of plant adaption to abiotic stress, which deepen our understanding of the molecular mechanisms of abiotic stress regulation in plants.

Genome-Wide Identification and Evolutionary Analysis of Gossypium YTH Domain-Containing RNA-Binding Protein Family and the Role of GhYTH8 in Response to Drought Stress

YTH domain-containing proteins are one kind of RNA-binding protein involved in post-transcriptional regulation and play multiple roles in regulating the growth, development, and abiotic stress responses of plants. However, the YTH domain-containing RNA-binding protein family has not been previously studied in cotton. In this study, a total of 10, 11, 22, and 21 YTH genes were identified in Gossypium arboreum, Gossypium raimondii, Gossypium barbadense, and Gossypium hirsutum, respectively. These Gossypium YTH genes were categorized into three subgroups by phylogenetic analysis. The chromosomal distribution, synteny analysis, structures of Gossypium YTH genes, and the motifs of YTH proteins were analyzed. Furthermore, the cis-element of GhYTH genes promoter, miRNA targets of GhYTH genes, and subcellular localization of GhYTH8 and GhYTH16 were characterized. Expression patterns of GhYTH genes in different tissues, organs, and in response to different stresses were also analyzed. Moreover, functional verifications revealed that silencing GhYTH8 attenuated the drought tolerance in the upland cotton TM-1 line. These findings provide useful clues for the functional and evolutionary analysis of YTH genes in cotton.

The wheat WRKY transcription factor TaWRKY1-2D confers drought resistance in transgenic Arabidopsis and wheat (Triticum aestivum L.)

The WRKY transcription factor family has been associated with a variety of plant biological processes, such as biotic and abiotic stress responses. In this study, 13 wheat TaWRKY DEGs in transcriptome data before and after drought stress, namely TaWRKY1 to TaWRKY8, including various copies, were identified and classified as Group I, II, or III. TaWRKY1-2D overexpression enhanced drought tolerance in transgenic Arabidopsis. Moreover, the AtRD29A, AtP5CS1, AtPOD1, AtCAT1, and AtSOD (Cu/Zn) genes, which are related to the stress response and antioxidant system, were significantly upregulated in TaWRKY1-2D transgenic Arabidopsis under drought stress. TaWRKY1-2 silencing in wheat increases the MDA content, reduces the contents of proline and chlorophyll and the activities of antioxidant enzymes, and inhibits the expression levels of antioxidant (TaPOD, TaCAT, and TaSOD (Fe))- and stress-related genes (TaP5CS) under drought stress. Yeast two-hybrid screening revealed TaDHN3 as an interaction partner of TaWRKY1-2D; their interaction was further confirmed using yeast two-hybrid and bimolecular fluorescence complementation. Furthermore, TaWRKY1-2D may play essential roles in wheat drought tolerance through posttranslational regulation of TaDHN3. Overall, these findings contribute to our knowledge of the WRKY family in wheat and identify TaWRKY1-2D as a promising candidate gene for improving wheat breeding to generate drought-tolerant wheat.

BPL3 binds the long non-coding RNA nalncFL7 to suppress FORKED-LIKE7 and modulate HAI1-mediated MPK3/6 dephosphorylation in plant immunity

RNA-binding proteins (RBPs) participate in a diverse set of biological processes in plants, but their functions and underlying mechanisms in plant-pathogen interactions are largely unknown. We previously showed that Arabidopsis thaliana BPA1-LIKE PROTEIN3 (BPL3) belongs to a conserved plant RBP family and negatively regulates reactive oxygen species (ROS) accumulation and cell death under biotic stress. In this study, we demonstrate that BPL3 suppresses FORKED-LIKE7 (FL7) transcript accumulation and raises levels of the cis-natural antisense long non-coding RNA (lncRNA) of FL7 (nalncFL7). FL7 positively regulated plant immunity to Phytophthora capsici while nalncFL7 negatively regulated resistance. We also showed that BPL3 directly binds to and stabilizes nalncFL7. Moreover, nalncFL7 suppressed accumulation of FL7 transcripts. Furthermore, FL7 interacted with HIGHLY ABA-INDUCED PP2C1 (HAI1), a type 2C protein phosphatase, and inhibited HAI1 phosphatase activity. By suppressing HAI1 activity, FL7 increased the phosphorylation levels of MITOGEN-ACTIVATED PROTEIN KINASE 3 (MPK3) and MPK6, thus enhancing immunity responses. BPL3 and FL7 are conserved in all plant species tested, but the BPL3-nalncFL7-FL7 cascade was specific to the Brassicaceae. Thus, we identified a conserved BPL3-nalncFL7-FL7 cascade that coordinates plant immunity.

SlRBP1 promotes translational efficiency via SleIF4A2 to maintain chloroplast function in tomato

Many glycine-rich RNA-binding proteins (GR-RBPs) have critical functions in RNA processing and metabolism. Here, we describe a role for the tomato (Solanum lycopersicum) GR-RBP SlRBP1 in regulating mRNA translation. We found that SlRBP1 knockdown mutants (slrbp1) displayed reduced accumulation of total chlorophyll and impaired chloroplast ultrastructure. These phenotypes were accompanied by deregulation of the levels of numerous key transcripts associated with chloroplast functions in slrbp1. Furthermore, native RNA immunoprecipitation-sequencing (nRIP-seq) recovered 61 SlRBP1-associated RNAs, most of which are involved in photosynthesis. SlRBP1 binding to selected target RNAs was validated by nRIP-qPCR. Intriguingly, the accumulation of proteins encoded by SlRBP1-bound transcripts, but not the mRNAs themselves, was reduced in slrbp1 mutants. Polysome profiling followed by RT-qPCR assays indicated that the polysome occupancy of target RNAs was lower in slrbp1 plants than in wild-type. Furthermore, SlRBP1 interacted with the eukaryotic translation initiation factor SleIF4A2. Silencing of SlRBP1 significantly reduced SleIF4A2 binding to SlRBP1-target RNAs. Taking these observations together, we propose that SlRBP1 binds to and channels RNAs onto the SleIF4A2 translation initiation complex and promotes the translation of its target RNAs to regulate chloroplast functions.

Phosphorylated viral protein evades plant immunity through interfering the function of RNA-binding protein

Successful pathogen infection in plant depends on a proper interaction between the invading pathogen and its host. Post-translational modification (PTM) plays critical role(s) in plant-pathogen interaction. However, how PTM of viral protein regulates plant immunity remains poorly understood. Here, we found that S162 and S165 of Chinese wheat mosaic virus (CWMV) cysteine-rich protein (CRP) are phosphorylated by SAPK7 and play key roles in CWMV infection. Furthermore, the phosphorylation-mimic mutant of CRP (CRP^S162/165D) but not the non-phosphorylatable mutant of CRP (CRP^S162/165A) interacts with RNA-binding protein UBP1-associated protein 2C (TaUBA2C). Silencing of TaUBA2C expression in wheat plants enhanced CWMV infection. In contrast, overexpression of TaUBA2C in wheat plants inhibited CWMV infection. TaUBA2C inhibits CWMV infection through recruiting the pre-mRNA of TaNPR1, TaPR1 and TaRBOHD to induce cell death and H₂O₂ production. This effect can be supressed by CRP^S162/165D through changing TaUBA2C chromatin-bound status and attenuating it’s the RNA- or DNA-binding activities. Taken together, our findings provide new knowledge on how CRP phosphorylation affects CWMV infection as well as the arms race between virus and wheat plants.

Chinese wheat mosaic virus (CWMV) causes a damaging disease in cereal plants. However, CWMV interacts with host factors to facilitate virus infection is not clear yet. Here, we found that S162 and S165 of CWMV cysteine-rich protein (CRP) are phosphorylated by SAPK7 in vivo and in vitro. Mutational analyses have indicated that these two phosphorylation sites of CRP (CRP^S162/165D) promoting CWMV infection in plants, due to the supressed cell death and H₂O₂ production. Further investigations found the CRP^S162/165D can interact with TaUBA2C, while the non-phosphorylatable mutant of CRP (CRP^S162/165A) does not. Futhermore, we have determined that CRP^S162/165D and TaUBA2C interaction inhibited the formation of TaUBA2C speckles in nucleus to attenuate its RNA- and DNA-binding activity. We also showed that TaUBA2C recruit the pre-mRNA of TaNPR1, TaPR1 and TaRBOHD to up-regulated these genes expressions and then induce cell death and H₂O₂ production in plant. This effect can be supressed by the expression of CRP^S162/165D, in a dose-dependent manner. Taken together, our discovery may provide a new sight for the arms race between virus and its host plants.

PRIP: A Protein-RNA Interface Predictor Based on Semantics of Sequences

RNA–protein interactions play an indispensable role in many biological processes. Growing evidence has indicated that aberration of the RNA–protein interaction is associated with many serious human diseases. The precise and quick detection of RNA–protein interactions is crucial to finding new functions and to uncovering the mechanism of interactions. Although many methods have been presented to recognize RNA-binding sites, there is much room left for the improvement of predictive accuracy. We present a sequence semantics-based method (called PRIP) for predicting RNA-binding interfaces. The PRIP extracted semantic embedding by pre-training the Word2vec with the corpus. Extreme gradient boosting was employed to train a classifier. The PRIP obtained a SN of 0.73 over the five-fold cross validation and a SN of 0.67 over the independent test, outperforming the state-of-the-art methods. Compared with other methods, this PRIP learned the hidden relations between words in the context. The analysis of the semantics relationship implied that the semantics of some words were specific to RNA-binding interfaces. This method is helpful to explore the mechanism of RNA–protein interactions from a semantics point of view.

Detection of Single Nucleotide Polymorphism (SNP) Variation of a Gene Sequence on Membrane-Based Lateral-Flow Strips

This study used appropriate primers to distinguish the gene model, HLA-A31:01, on membrane-based lateral-flow (MBLF) strips from its allele, which is with an SNP. Using primers designed with a mismatch base on one or two sides next to the SNP spot was verified as a good approach. In the optimal condition, the detection limits of 1~0.1 ng/μL nucleotides were in agreement with reports in the literature, and the intra- and inter-assay tests ensured the detection reproducibility of this approach with CV% of 2.5%~15.9% and 1.7%~14.7%, respectively. The detection specificity was also validated by the tests on the selected negative-control genes. The tests on MBLF strips in this study showed an easy, robust, reproducible, and reliable detection methodology for untrained personnel at care points with limited instrument and particularly for avoiding medications from faulty prescriptions.

Alternative Splicing Dynamics During the Lifecycle of Salvia miltiorrhiza Root Revealed the Fine Tuning in Root Development and Ingredients Biosynthesis

Alternative splicing (AS) is an essential post-transcriptional process that enhances the coding and regulatory potential of the genome, thereby strongly influencing multiple plant physiology processes, such as metabolic biosynthesis. To explore how AS affects the root development and synthesis of tanshinones and phenolic acid pathways in Salvia miltiorrhiza roots, we investigated the dynamic landscape of AS events in S. miltiorrhiza roots during an annual life history. Temporal profiling represented a distinct temporal variation of AS during the entire development stages, showing the most abundant AS events at the early seedling stage (ES stage) and troughs in 45 days after germination (DAG) and 120 DAG. Gene ontology (GO) analysis indicated that physiological and molecular events, such as lateral root formation, gravity response, RNA splicing regulation, and mitogen-activated protein kinase (MAPK) cascade, were greatly affected by AS at the ES stage. AS events were identified in the tanshinones and phenolic acids pathways as well, especially for the genes for the branch points of the pathways as SmRAS and SmKSL1. Fifteen Ser/Arg-rich (SR) proteins and eight phosphokinases (PKs) were identified with high transcription levels at the ES stage, showing their regulatory roles for the high frequency of AS in this stage. Simultaneously, a co-expression network that includes 521 highly expressed AS genes, SRs, and PKs, provides deeper insight into the mechanism for the variable programming of AS.

The mRNA-binding proteome of a critical phase transition during Arabidopsis seed germination

Arabidopsis thaliana seed germination is marked by extensive translational control at two critical phase transitions. The first transition refers to the start of hydration, the hydration translational shift. The second shift, the germination translational shift (GTS) is the phase between testa rupture and radicle protrusion at which the seed makes the all or nothing decision to germinate. The mechanism behind the translational regulation at these phase transitions is unknown. RNA binding proteins (RBPs) are versatile players in the post-transcriptional control of messenger RNAs (mRNAs) and as such candidates for regulating translation during seed germination. Here, we report the mRNA binding protein repertoire of seeds during the GTS. Thirty seed specific RBPs and 22 dynamic RBPs were identified during the GTS, like the putative RBP Vacuolar ATPase subunit A and RBP HSP101. Several stress granule markers were identified in this study, which suggests that seeds are prepared to quickly adapt the translation of specific mRNAs in response to changes in environmental conditions during the GTS. Taken together this study provides a detailed insight into the world of RBPs during seed germination and their possible regulatory role during this developmentally regulated process.

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.

Genome-Scale Computational Identification and Characterization of UTR Introns in Atalantia buxifolia

Accumulated evidence has shown that CDS introns (CIs) play important roles in regulating gene expression. However, research on UTR introns (UIs) is limited. In this study, UIs (including 5′UTR and 3′UTR introns (5UIs and 3UIs)) were identified from the Atalantia buxifolia genome. The length and nucleotide distribution characteristics of both 5UIs and 3UIs and the distributions of cis-acting elements and transcription factor binding sites (TFBSs) in 5UIs were investigated. Moreover, PageMan enrichment analysis was applied to show the possible roles of transcripts containing UIs (UI-Ts). In total, 1077 5UIs and 866 3UIs were identified from 897 5UI-Ts and 670 3UI-Ts, respectively. Among them, 765 (85.28%) 5UI-Ts and 527 (78.66%) 3UI-Ts contained only one UI, and 94 (6.38%) UI-Ts contained both 5UI and 3UI. The UI density was lower than that of CDS introns, but their mean and median intron sizes were ~2 times those of the CDS introns. The A. buxifolia 5UIs were rich in gene-expression-enhancement-related elements and contained many TFBSs for BBR-BPC, MIKC_MADS, AP2 and Dof TFs, indicating that 5UIs play a role in regulating or enhancing the expression of downstream genes. Enrichment analysis revealed that UI-Ts involved in ‘not assigned’ and ‘RNA’ pathways were significantly enriched. Noteworthily, 119 (85.61%) of the 3UI-Ts were genes encoding pentatricopeptide (PPR) repeat-containing proteins. These results will be helpful for the future study of the regulatory roles of UIs in A. buxifolia.

RNA-Binding Motif Protein 11 (RBM11) Serves as a Prognostic Biomarker and Promotes Ovarian Cancer Progression

Ovarian cancer is one of the most lethal gynecologic malignancies for women. Due to the lack of efficient target therapy, the overall survival rate for patients with advanced ovarian cancer is still low. Illustrating the molecular mechanisms dictating ovarian cancer progression is critically important to develop novel therapeutic agents. Here, we found that RNA-binding motif protein 11 (RBM11) was highly elevated in ovarian cancer tissues compared with normal ovary, while RBM11 depletion in ovarian cancer cells resulted in impaired cell growth and invasion. Moreover, knockdown of RBM11 also retarded tumor growth in the A2780 ovarian cancer xenograft model. Mechanically, we found that RBM11 positively regulated Akt/mTOR signaling pathway activation in ovarian cancer cells. Thus, these results identify RBM11 is a novel oncogenic protein and prognostic biomarker for ovarian cancers.

Plant Stress Granules: Trends and Beyond

Stress granules (SGs) are dynamic membrane-less condensates transiently assembled through liquid-liquid phase separation (LLPS) in response to stress. SGs display a biphasic architecture constituted of core and shell phases. The core is a conserved SG fraction fundamental for its assembly and consists primarily of proteins with intrinsically disordered regions and RNA-binding domains, along with translational-related proteins. The shell fraction contains specific SG components that differ among species, cell type, and developmental stage and might include metabolic enzymes, receptors, transcription factors, untranslated mRNAs, and small molecules. SGs assembly positively correlates with stalled translation associated with stress responses playing a pivotal role during the adaptive cellular response, post-stress recovery, signaling, and metabolic rewire. After stress, SG disassembly releases mRNA and proteins to the cytoplasm to reactivate translation and reassume cell growth and development. However, under severe stress conditions or aberrant cellular behavior, SG dynamics are severely disturbed, affecting cellular homeostasis and leading to cell death in the most critical cases. The majority of research on SGs has focused on yeast and mammals as model organism. Nevertheless, the study of plant SGs has attracted attention in the last few years. Genetics studies and adapted techniques from other non-plant models, such as affinity capture coupled with multi-omics analyses, have enriched our understanding of SG composition in plants. Despite these efforts, the investigation of plant SGs is still an emerging field in plant biology research. In this review, we compile and discuss the accumulated progress of plant SGs regarding their composition, organization, dynamics, regulation, and their relation to other cytoplasmic foci. Lastly, we will explore the possible connections among the most exciting findings of SGs from mammalian, yeast, and plants, which might help provide a complete view of the biology of plant SGs in the future.

The Pumilio RNA-binding protein APUM24 regulates seed maturation by fine-tuning the BPM-WRI1 module in Arabidopsis

Pumilio RNA-binding proteins participate in messenger RNA (mRNA) degradation and translational repression, but their roles in plant development are largely unclear. Here, we show that Arabidopsis PUMILIO PROTEIN24 (APUM24), an atypical Pumilio-homology domain-containing protein, plays an important part in regulating seed maturation, a major stage of plant development. APUM24 is strongly expressed in maturing seeds. Reducing APUM24 expression resulted in abnormal seed maturation, wrinkled seeds, and lower seed oil contents, and APUM24 knockdown resulted in lower levels of WRINKLED 1 (WRI1), a key transcription factor controlling seed oil accumulation, and lower expression of WRI1 target genes. APUM24 reduces the mRNA stability of BTB/POZMATH (BPM) family genes, thus decreasing BPM protein levels. BPM is responsible for the 26S proteasome-mediated degradation of WRI1 and has important functions in plant growth and development. The 3' untranslated regions of BPM family genes contain putative Pumilio response elements (PREs), which are bound by APUM24. Reduced BPM or increased WRI1 expression rescued the deficient seed maturation of apum24-2 knockdown mutants, and APUM24 overexpression resulted in increased seed size and weight. Therefore, APUM24 is crucial to seed maturation through its action as a positive regulator fine-tuning the BPM-WRI1 module, making APUM24 a promising target for breeding strategies to increase crop yields.

A historical overview of long-distance signalling in plants

Be it a small herb or a large tree, intra- and intercellular communication and long-distance signalling between distant organs are crucial for every aspect of plant development. The vascular system, comprising xylem and phloem, acts as a major conduit for the transmission of long-distance signals in plants. In addition to expanding our knowledge of vascular development, numerous reports in the past two decades revealed that selective populations of RNAs, proteins, and phytohormones function as mobile signals. Many of these signals were shown to regulate diverse physiological processes, such as flowering, leaf and root development, nutrient acquisition, crop yield, and biotic/abiotic stress responses. In this review, we summarize the significant discoveries made in the past 25 years, with emphasis on key mobile signalling molecules (mRNAs, proteins including RNA-binding proteins, and small RNAs) that have revolutionized our understanding of how plants integrate various intrinsic and external cues in orchestrating growth and development. Additionally, we provide detailed insights on the emerging molecular mechanisms that might control the selective trafficking and delivery of phloem-mobile RNAs to target tissues. We also highlight the cross-kingdom movement of mobile signals during plant-parasite relationships. Considering the dynamic functions of these signals, their implications in crop improvement are also discussed.

A Tandem Mass Tags (TMTs) labeling approach highlights differences between the shoot proteome of two Arabidopsis thaliana ecotypes, Col-0 and Ws

Arabidopsis has become a powerful model to study morphogenesis, plant growth, development but also plant response to environmental conditions. Over 1000 Arabidopsis genomes are available and show natural genetic variations. Among them, the main reference accessions Wassilewskija (Ws) and Columbia (Col-0), originally growing at contrasted altitudes and temperatures, are widely studied, but data contributing to their molecular phenotyping are still scarce. A global quantitative proteomics approach using isobaric stable isotope labeling (Tandem Mass Tags, TMT) was performed on Ws and Col-0. Plants have been hydroponically grown at 16 h/8 h (light/dark cycle) at 23°C day/19°C night for three weeks. A TMT labeling of the proteins extracted from their shoots has been performed and showed a differential pattern of protein abundance between them. These results have allowed identifying several proteins families possibly involved in the differential responses observed for Ws and Col-0 during plant development and upon environmental changes. In particular, Ws and Col-0 mainly differ in photosynthesis, cell wall-related proteins, plant defense/stress, ROS scavenging enzymes/redox homeostasis and DNA/RNA binding/transcription/translation/protein folding.

The role of RNA-binding protein, microRNA and alternative splicing in seed germination: a field need to be discovered

Seed germination is the process through which a quiescent organ reactivates its metabolism culminating with the resumption cell divisions. It is usually the growth of a plant contained within a seed and results in the formation of a seedling. Post-transcriptional regulation plays an important role in gene expression. In cells, post-transcriptional regulation is mediated by many factors, such as RNA-binding proteins, microRNAs, and the spliceosome. This review provides an overview of the relationship between seed germination and post-transcriptional regulation. It addresses the relationship between seed germination and RNA-binding proteins, microRNAs and alternative splicing. This presentation of the current state of the knowledge will promote new investigations into the relevance of the interactions between seed germination and post-transcriptional regulation in plants.

The Rice GLYCINE-RICH PROTEIN 3 Confers Drought Tolerance by Regulating mRNA Stability of ROS Scavenging-Related Genes

BACKGROUND

Plant glycine-rich proteins are categorized into several classes based on their protein structures. The glycine-rich RNA binding proteins (GRPs) are members of class IV subfamily possessing N-terminus RNA-recognition motifs (RRMs) and proposed to be involved in post-transcriptional regulation of its target transcripts. GRPs are involved in developmental process and cellular stress responses, but the molecular mechanisms underlying these regulations are still elusive.

RESULTS

Here, we report the functional characterization of rice GLYCINE-RICH PROTEIN 3 (OsGRP3) and its physiological roles in drought stress response. Both drought stress and ABA induce the expression of OsGRP3. Transgenic plants overexpressing OsGRP3 (OsGRP3^OE) exhibited tolerance while knock-down plants (OsGRP3^KD) were susceptible to drought compared to the non-transgenic control. In vivo, subcellular localization analysis revealed that OsGRP3-GFP was transported from cytoplasm/nucleus into cytoplasmic foci following exposure to ABA and mannitol treatments. Comparative transcriptomic analysis between OsGRP3^OE and OsGRP3^KD plants suggests that OsGRP3 is involved in the regulation of the ROS related genes. RNA-immunoprecipitation analysis revealed the associations of OsGRP3 with PATHOGENESIS RELATED GENE 5 (PR5), METALLOTHIONEIN 1d (MT1d), 4,5-DOPA-DIOXYGENASE (DOPA), and LIPOXYGENASE (LOX) transcripts. The half-life analysis showed that PR5 transcripts decayed slower in OsGRP3^OE but faster in OsGRP3^KD, while MT1d and LOX transcripts decayed faster in OsGRP3^OE but slower in OsGRP3^KD plants. H₂O₂ accumulation was reduced in OsGRP3^OE and increased in OsGRP3^KD plants compared to non-transgenic plants (NT) under drought stress.

CONCLUSION

OsGRP3 plays a positive regulator in rice drought tolerance and modulates the transcript level and mRNA stability of stress-responsive genes, including ROS-related genes. Moreover, OsGRP3 contributes to the reduction of ROS accumulation during drought stress. Our results suggested that OsGRP3 alleviates ROS accumulation by regulating ROS-related genes' mRNA stability under drought stress, which confers drought tolerance.

The Landscape of RNA-Protein Interactions in Plants: Approaches and Current Status

RNAs transmit information from DNA to encode proteins that perform all cellular processes and regulate gene expression in multiple ways. From the time of synthesis to degradation, RNA molecules are associated with proteins called RNA-binding proteins (RBPs). The RBPs play diverse roles in many aspects of gene expression including pre-mRNA processing and post-transcriptional and translational regulation. In the last decade, the application of modern techniques to identify RNA-protein interactions with individual proteins, RNAs, and the whole transcriptome has led to the discovery of a hidden landscape of these interactions in plants. Global approaches such as RNA interactome capture (RIC) to identify proteins that bind protein-coding transcripts have led to the identification of close to 2000 putative RBPs in plants. Interestingly, many of these were found to be metabolic enzymes with no known canonical RNA-binding domains. Here, we review the methods used to analyze RNA-protein interactions in plants thus far and highlight the understanding of plant RNA-protein interactions these techniques have provided us. We also review some recent protein-centric, RNA-centric, and global approaches developed with non-plant systems and discuss their potential application to plants. We also provide an overview of results from classical studies of RNA-protein interaction in plants and discuss the significance of the increasingly evident ubiquity of RNA-protein interactions for the study of gene regulation and RNA biology in plants.

AtMAD: Arabidopsis thaliana multi-omics association database

Integration analysis of multi-omics data provides a comprehensive landscape for understanding biological systems and mechanisms. The abundance of high-quality multi-omics data (genomics, transcriptomics, methylomics and phenomics) for the model organism Arabidopsis thaliana enables scientists to study the genetic mechanism of many biological processes. However, no resource is available to provide comprehensive and systematic multi-omics associations for Arabidopsis. Here, we developed an Arabidopsis thaliana Multi-omics Association Database (AtMAD, http://www.megabionet.org/atmad), a public repository for large-scale measurements of associations between genome, transcriptome, methylome, pathway and phenotype in Arabidopsis, designed for facilitating identification of eQTL, emQTL, Pathway-mQTL, Phenotype-pathway, GWAS, TWAS and EWAS. Candidate variants/methylations/genes were identified in AtMAD for specific phenotypes or biological processes, many of them are supported by experimental evidence. Based on the multi-omics association strategy, we have identified 11 796 cis-eQTLs and 10 119 trans-eQTLs. Among them, 68 837 environment-eQTL associations and 149 622 GWAS-eQTL associations were identified and stored in AtMAD. For expression–methylation quantitative trait loci (emQTL), we identified 265 776 emQTLs and 122 344 pathway-mQTLs. For TWAS and EWAS, we obtained 62 754 significant phenotype-gene associations and 3 993 379 significant phenotype-methylation associations, respectively. Overall, the multi-omics associated network in AtMAD will provide new insights into exploring biological mechanisms of plants at multi-omics levels.

Bruchid beetle ovipositioning mediated defense responses in black gram pods

BACKGROUND

Black gram [Vigna mungo (L)] seeds are a rich source of digestible protein and dietary fibre, both for human and animal consumption. However, the quality and quantity of the Vigna seeds are severely affected by bruchid beetles during storage. Therefore, analyses of the expression of the bruchid induced transcript dynamics in black gram pods would be helpful to understand the underlying defense mechanism against bruchid oviposition.

RESULTS

We used the RNAseq approach to survey the changes in transcript profile in the developing seeds of a moderately resistant cultivar IC-8219 against bruchid oviposition using a susceptible cultivar T-9 as a control. A total of 96,084,600 and 99,532,488 clean reads were generated from eight (4 each) samples of IC-8219 and T-9 cultivar, respectively. Based on the BLASTX search against the NR database, 32,584 CDSs were generated of which 31,817 CDSs were significantly similar to Vigna radiata, a close relative of Vigna mungo. The IC-8219 cultivar had 630 significantly differentially expressed genes (DEGs) of which 304 and 326 genes up and down-regulated, respectively. However, in the T-9 cultivar, only 168 DEGs were identified of which 142 and 26 genes up and down-regulated, respectively. The expression analyses of 10 DEGs by qPCR confirmed the accuracy of the RNA-Seq data. Gene Ontology and KEGG pathway analyses helped us to better understand the role of these DEGs in oviposition mediated defense response of black gram. In both the cultivars, the most significant transcriptomic changes in response to the oviposition were related to the induction of defense response genes, transcription factors, secondary metabolites, enzyme inhibitors, and signal transduction pathways. It appears that the bruchid ovipositioning mediated defense response in black gram is induced by SA signaling pathways and defense genes such as defensin, genes for secondary metabolites, and enzyme inhibitors could be potential candidates for resistance to bruchids.

CONCLUSION

We generated a transcript profile of immature black gram pods upon bruchid ovipositioning by de novo assembly and studied the underlying defense mechanism of a moderately resistant cultivar.

Cysteine modifications (oxPTM) and protein sulphenylation-mediated sulfenome expression in plants: evolutionary conserved signaling networks?

Plant resilience to oxidative stress possibly operates through the restoration of intracellular redox milieu and the activity of various posttranslationally modified proteins. Among various modes of redox regulation operative in plants cys oxPTMs are brought about by the activity of reactive oxygen species (ROS), reactive nitrogen species (RNS), and hydrogen peroxide. Cysteine oxPTMs are capable of transducing ROS-mediated long-distance hormone signaling (ABA, JA, SA) in plants. S-sulphenylation is an intermediary modification en route to other oxidative states of cysteine. In silico analysis have revealed evolutionary conservation of certain S-sulphenylated proteins across human and plants. Further analysis of protein sulphenylation in plants should be extended to the functional follow-up studies followed by site-specific characterization and case-by-case validation of protein activity. The repertoire of physiological methods (fluorescent conjugates (dimedone) and yeast AP-1 (YAP1)-based genetic probes) in the recent past has been successful in the detection of sulphenylated proteins and other cysteine-based modifications in plants. In view of a better understanding of the sulfur-based redoxome it is necessary to update our timely progress on the methodological advancements for the detection of cysteine-based oxPTM. This substantiative information can extend our investigations on plant-environment interaction thus improving crop manipulation strategies. The simulation-based computational approach has emerged as a new method to determine the directive mechanism of cysteine oxidation in plants. Thus, sulfenome analysis in various plant systems might reflect as a pinnacle of plant redox biology in the future.

NtRBP45, a nuclear RNA-binding protein of Nicotiana tabacum, facilitates post-transcriptional gene silencing

The tobacco RBP45 is a nuclear RNA binding protein (RBP). In this study, we identified that the gene expression of NtRBP45 was significantly up-regulated upon the Tobacco mosaic virus infection and the central region of the protein accounted for its nuclear localization. In particular, using a green fluorescent protein-based transient suppression assay, we uncovered that the transiently overexpressed NtRBP45 was able to enhance local post-transcriptional gene silencing (PTGS), facilitate siRNA accumulation, and compromise the RNA silencing suppression mediated by Tomato aspermy virus 2b protein. Deletion mutagenesis showed that both the N- and C-terminal regions of NtRBP45 were necessary for enhancing PTGS. The data overall indicated a novel RNA silencing factor that might participate in antiviral defense.

The Arabidopsis KH-domain protein FLOWERING LOCUS Y delays flowering by upregulating FLOWERING LOCUS C family members

We identified FLY as a previously uncharacterized RNA-binding-family protein that controls flowering time by positively regulating the expression of FLC clade members. The ability of flowering plants to adjust the timing of the floral transition based on endogenous and environmental signals contributes to their adaptive success. In Arabidopsis thaliana, the MADS-domain protein FLOWERING LOCUS C (FLC) and the FLC clade members FLOWERING LOCUS M/MADS AFFECTING FLOWERING1 (FLM/MAF1), MAF2, MAF3, MAF4, and MAF5 form nuclear complexes that repress flowering under noninductive conditions. However, how FLM/MAF genes are regulated requires further study. Using a genetic strategy, we showed that the previously uncharacterized K-homology (KH) domain protein FLOWERING LOCUS Y (FLY) modulates flowering time. The fly-1 knockout mutant and FLY artificial microRNA knockdown line flowered earlier than the wild type under long- and short-day conditions. The knockout fly-1 allele, a SALK T-DNA insertion mutant, contains an ~ 110-kb genomic deletion induced by T-DNA integration. FLC clade members were downregulated in the fly-1 mutants and FLY artificial microRNA knockdown line, whereas the level of the FLC antisense transcript COOLAIR was similar to that of the wild type. Our results identify FLY as a regulator that affects flowering time through upregulation of FLC clade members.

Natural variation in glycine-rich region of Brassica oleracea cold shock domain protein 5 (BoCSDP5) is associated with low temperature tolerance

BACKGROUND

Low temperature (LT) or cold stress is a major environmental stress that seriously affects plant growth and development, limiting crop productivity. Cold shock domain proteins (CSDPs), which are present in most living organism, are involved in RNA metabolisms influencing abiotic stress tolerance.

OBJECTIVE

The aims of this study are to identify target gene for LT-tolerance, like CSDPs, characterize genetics, and develop molecular marker distinguishing LT-tolerance in cabbage (Brassica oleracea var. capitata).

METHODS

Semi-quantitative RT-PCR or qRT-PCR was used in gene expression study. LT-tolerance was determined by electrolyte leakage and PCR with allelic specific primers.

RESULTS

Allelic variation was found in BoCSDP5 coding sequence (CDs) between LT-tolerant (BN106 and BN553) and -susceptible inbred lines (BN107 and BN554). LT-tolerant inbred lines contained variant type of BoCSDP5 (named as BoCSDP5v) which encodes extra CCHC zinc finger domain at C-terminus. Association of LT-tolerance with BoCSDP5v was confirmed by electrolyte leakage and segregation using genetic population derived from BN553 and BN554 cross. Allelic variation in BoCSDP5 gene does not influence the rate of gene expression, but produces different proteins with different number of CCHC zinc finger domains. LT-tolerance marker designed on the basis of polymorphism between BoCSDP5 and BoCSDP5v was confirmed with samples used in previous B. oleracea CIRCADIAN CLOCK ASSOCIATED 1 (BoCCA1) marker validation.

CONCLUSIONS

LT-tolerant allele (BoCSDP5v) is dominant and independent of CBF pathway, and sufficient to generate molecular markers to identify LT-tolerant cabbage when it is used in combination with another marker, like BoCCA1-derived one. Production and analysis of overexpressing plants of BoCSDP1, BoCSDP3, BoCSDP5 and BoCSDP5v will be required for elucidating the function of CCHC zinc finger domains in LT-tolerance.

Emerging Roles of RNA-Binding Proteins in Seed Development and Performance

Seed development, dormancy, and germination are key physiological events that are not only important for seed generation, survival, and dispersal, but also contribute to agricultural production. RNA-binding proteins (RBPs) directly interact with target mRNAs and fine-tune mRNA metabolism by governing post-transcriptional regulation, including RNA processing, intron splicing, nuclear export, trafficking, stability/decay, and translational control. Recent studies have functionally characterized increasing numbers of diverse RBPs and shown that they participate in seed development and performance, providing significant insight into the role of RBP-mRNA interactions in seed processes. In this review, we discuss recent research progress on newly defined RBPs that have crucial roles in RNA metabolism and affect seed development, dormancy, and germination.

Protein-ensemble-RNA docking by efficient consideration of protein flexibility through homology models

MOTIVATION

Given the importance of protein-ribonucleic acid (RNA) interactions in many biological processes, a variety of docking algorithms have been developed to predict the complex structure from individual protein and RNA partners in the past decade. However, due to the impact of molecular flexibility, the performance of current methods has hit a bottleneck in realistic unbound docking. Pushing the limit, we have proposed a protein-ensemble-RNA docking strategy to explicitly consider the protein flexibility in protein-RNA docking through an ensemble of multiple protein structures, which is referred to as MPRDock. Instead of taking conformations from MD simulations or experimental structures, we obtained the multiple structures of a protein by building models from its homologous templates in the Protein Data Bank (PDB).

RESULTS

Our approach can not only avoid the reliability issue of structures from MD simulations but also circumvent the limited number of experimental structures for a target protein in the PDB. Tested on 68 unbound-bound and 18 unbound-unbound protein-RNA complexes, our MPRDock/DITScorePR considerably improved the docking performance and achieved a significantly higher success rate than single-protein rigid docking whether pseudo-unbound templates are included or not. Similar improvements were also observed when combining our ensemble docking strategy with other scoring functions. The present homology model-based ensemble docking approach will have a general application in molecular docking for other interactions.

AVAILABILITY AND IMPLEMENTATION

http://huanglab.phys.hust.edu.cn/mprdock/.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

Identification of genetic loci associated with forage quality in response to water deficit in autotetraploid alfalfa (Medicago sativa L.)

BACKGROUND

Alfalfa has been cultivated in many regions around the world as an important forage crop due to its nutritive value to livestock and ability to adapt to various environments. However, the genetic basis by which plasticity of quality-relevant traits influence alfalfa adaption to different water conditions remain largely unknown.

RESULTS

In the present study, 198 accessions of alfalfa of the core collection for drought tolerance were evaluated for 26 forage quality traits in a field trial under an imposed deficit irrigation gradient. Regression analysis between quality traits and water stress revealed that values of fiber-related traits were negatively correlated with values of energy-related traits as water deficit increased. More than one hundred significant markers associated with forage quality under different water treatments were identified using genome-wide association studies with genotyping by sequencing. Among them, 131 markers associated with multiple traits in all the water deficit treatments. Most of the associated markers were dependent to the levels of water deficit, suggesting genetic controls for forage quality traits were dependent to the stress treatment. Twenty-four loci associated with forage quality were annotated to functional genes that may play roles in cell development or in response to water stress.

CONCLUSIONS

This study addressed the genetic base of phenotypic variation of forage quality traits under water deficit. The SNP markers identified in this study will be useful in marker-assisted selection for the genetic improvement of alfalfa with enhanced drought tolerance while maintaining forage quality.

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.

RALF1-FERONIA complex affects splicing dynamics to modulate stress responses and growth in plants

The environmentally responsive signaling pathways that link global transcriptomic changes through alternative splicing (AS) to plant fitness remain unclear. Here, we found that the interaction of the extracellular rapid alkalinization FACTOR 1 (RALF1) peptide with its receptor FERONIA (FER) triggered a rapid and massive RNA AS response by interacting with and phosphorylating glycine-rich RNA binding protein7 (GRP7) to elevate GRP7 nuclear accumulation in Arabidopsis thaliana. FER-dependent GRP7 phosphorylation enhanced its mRNA binding ability and its association with the spliceosome component U1-70K to enable splice site selection, modulating dynamic AS. Genetic reversal of a RALF1-FER-dependent splicing target partly rescued mutants deficient in GRP7. AS of GRP7 itself induced nonsense-mediated decay feedback to the RALF1-FER-GRP7 module, fine-tuning stress responses, and cell growth. The RALF1-FER-GRP7 module provides a paradigm for regulatory mechanisms of RNA splicing in response to external stimuli.

OsRRM, an RNA-Binding Protein, Modulates Sugar Transport in Rice (Oryza sativa L.)

Sugar allocation between vegetative and reproductive tissues is vital to plant development, and sugar transporters play fundamental roles in this process. Although several transcription factors have been identified that control their transcription levels, the way in which the expression of sugar transporter genes is controlled at the posttranscriptional level is unknown. In this study, we showed that OsRRM, an RNA-binding protein, modulates sugar allocation in tissues on the source-to-sink route. The OsRRM expression pattern partly resembles that of several sugar transporter and transcription factor genes that specifically affect sugar transporter gene expression. The messenger RNA levels of almost all of the sugar transporter genes are severely reduced in the osrrm mutant, and this alters sugar metabolism and sugar signaling, which further affects plant height, flowering time, seed size, and starch synthesis. We further showed that OsRRM binds directly to messenger RNAs encoded by sugar transporter genes and thus may stabilize their transcripts. Therefore, we have uncovered the physiological function of OsRRM, which sheds new light on sugar metabolism and sugar signaling.