Regulation of Abiotic Stress Responses in Plants through RNA-binding Protein-mediated Alternative Splicing

Qian Li^*
*Correspondence: Qian Li, Department of Biochemistry and Molecular Biology, Hebrew University, Israel, Email:

Introduction

Abiotic stresses such as drought, salinity, extreme temperatures, and nutrient deficiencies significantly impact plant growth and productivity, posing a challenge to global food security. Plants, as sessile organisms, have evolved intricate molecular mechanisms to perceive and respond to these environmental stresses. Among these mechanisms, Alternative Splicing (AS) of pre-mRNA plays a critical role in regulating gene expression and producing proteomic diversity, allowing plants to adapt to adverse conditions. Rna- Binding Proteins (RBPs) are pivotal in mediating alternative splicing, enabling plants to fine-tune their stress responses. RNA-binding proteins interact with pre-mRNA molecules to regulate various aspects of RNA metabolism, including splicing, stability, transport, and translation. By recognizing specific sequence motifs or structural elements in pre-mRNA, RBPs can modulate spliceosome assembly and influence the inclusion or exclusion of particular exons. This dynamic process generates multiple transcript variants from a single gene, thereby expanding the functional capacity of the plant genome. In the context of abiotic stress, RBPs act as key modulators, integrating environmental signals to orchestrate splicing decisions that impact stressresponsive pathways.

Description

Recent studies have highlighted the importance of specific RBPs in plant abiotic stress responses. For instance, SR (serine/arginine-rich) proteins and hnRNPs (heterogeneous nuclear ribonucleoproteins) are two major families of RBPs involved in splicing regulation. SR proteins are known to promote splice site recognition and exon inclusion, while hnRNPs often antagonize SR proteins to mediate exon skipping. Under stress conditions, the expression levels, subcellular localization, and activity of these RBPs are often altered, leading to stress-specific splicing patterns. For example, in Arabidopsis thaliana, the SR protein RS40 and the hnRNP-like protein RBP45 modulate alternative splicing events in genes related to osmotic stress tolerance. Such splicing changes often result in the production of stress-adaptive isoforms that enhance plant resilience. One prominent example of RBP-mediated alternative splicing involves the regulation of DREB2 (Dehydration-Responsive Element Binding Protein transcription factors. DREB2 proteins are crucial for drought and heat stress responses, but their activity is tightly regulated through alternative splicing. In rice, the RBP OsSKIP, a splicing factor homologous to human SKIP, modulates the splicing of DREB2B pre-mRNA. Under normal conditions, OsSKIP facilitates the production of a non-functional DREB2B isoform, while under drought stress, it promotes the splicing of a functional isoform, thereby activating downstream stress-responsive genes [1].

Another critical aspect of RBP-mediated alternative splicing in abiotic stress involves the regulation of ion transporters and channels. For example, alternative splicing of the SOS3 (Salt Overly Sensitive 3) gene, which encodes a calcium-binding protein involved in salinity tolerance, is modulated by RBPs. In Arabidopsis, the splicing factor STA1 has been implicated in the proper splicing of SOS3 pre-mRNA, ensuring the production of functional protein isoforms essential for ion homeostasis under salt stress. Such RBPmediated splicing events underscore the importance of post-transcriptional regulation in maintaining cellular homeostasis during abiotic stress. Emerging evidence also suggests that RBPs themselves are regulated at multiple levels in response to abiotic stress. Transcriptional induction, alternative splicing, post-translational modifications, and interactions with other proteins or RNAs can influence RBP activity and specificity. For instance, phosphorylation of SR proteins has been shown to modulate their splicing activity and subcellular localization in response to environmental cues. Additionally, RBPs may form complexes with non-coding RNAs, such as long non-coding RNAs (lncRNAs) or microRNAs (miRNAs), which can fine-tune their splicing functions under stress conditions [2].

The functional significance of RBP-mediated alternative splicing in abiotic stress responses is evident from the phenotypic consequences of RBP perturbations. Loss-of-function mutants or overexpression lines for specific RBPs often exhibit altered stress sensitivity. For example, Arabidopsis plants lacking the splicing factor AtGRP7 show impaired cold tolerance due to defective splicing of cold-responsive genes. Similarly, overexpression of OsHYP, an RBP involved in splicing regulation in rice, enhances drought and salinity tolerance by promoting the generation of stress-adaptive isoforms. The integration of high-throughput transcriptomic and proteomic approaches has provided valuable insights into the global impact of RBP-mediated alternative splicing on plant stress responses. RNA sequencing (RNA-seq) analyses have revealed widespread changes in splicing patterns under abiotic stress, with a significant proportion of stress-responsive genes undergoing alternative splicing. These studies have also identified novel RBPs and splicing factors associated with stress-specific splicing events. Proteomic analyses have further elucidated the functional consequences of alternative splicing by characterizing stress-induced protein isoforms and their roles in adaptive processes [3].

Despite these advances, many questions remain regarding the precise mechanisms by which RBPs regulate alternative splicing under abiotic stress. How do RBPs recognize and bind specific pre-mRNA targets in a stressdependent manner? What are the upstream signaling pathways that modulate RBP activity during stress? How do RBPs coordinate with other regulatory layers, such as transcription factors, epigenetic modifications, and RNA decay, to achieve a coherent stress response? Addressing these questions will require an interdisciplinary approach combining molecular genetics, biochemistry, bioinformatics, and systems biology. The potential applications of RBP-mediated alternative splicing in crop improvement are immense. By manipulating the expression or activity of specific RBPs, it may be possible to enhance stress tolerance in crops without compromising growth or yield. For instance, the targeted modulation of RBPs like OsSKIP or OsHYP could be employed to optimize splicing patterns in stress-responsive genes, conferring resilience to drought or salinity. Additionally, genome editing technologies such as CRISPR/Cas9 offer powerful tools to engineer precise changes in splicing regulatory elements or RBP-binding sites, enabling the generation of stress-tolerant crop varieties with tailored splicing profiles [4,5].

Conclusion

RNA-binding proteins and their role in alternative splicing represent a vital component of the plant’s response to abiotic stress. Through their ability to modulate gene expression and protein function at the post-transcriptional level, RBPs provide plants with the flexibility to adapt to dynamic environmental challenges. Continued research in this field holds great promise for unraveling the molecular intricacies of plant stress biology and translating these findings into innovative strategies for sustainable agriculture.

Acknowledgement

None.

Conflict of Interest

None.

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