AS-ABA · Alternative splicing and SR proteins in ABA-mediated plant stress responses

Alternative splicing and SR proteins in ABA-mediated plant stress responses

Abiotic stresses such as drought, high salinity, and extreme temperatures represent the most pervasive causes of loss of crop productivity worldwide. Therefore, a major goal in plant science is to understand how plants respond and withstand environmental stresses successfully. An adequate response to osmotic stress in plants involves endogenous accumulation of the hormone abscisic acid (ABA), which induces the activation of downstream effectors such as transcription factors and ion channels, resulting in the implementation of adaptive responses to withstand reduced water availability. While important research efforts have efficiently identified the transcriptional and posttranslational changes associated with plant responses to ABA, the posttranscriptional regulation of this hormonal pathway remains poorly explored. This project aims at understanding the role of alternative splicing, a process by which the same gene can generate multiple transcripts, during plant stress responses. This question is being addressed through the study of established important upstream modulators of this process, serine/arginine-rich (SR) proteins. SR proteins constitute a highly conserved family of RNA-binding proteins and are established important regulators of splicing. They affect splice sites in a concentration and phosphorylation-dependent manner and are conserved in all genomes known to undergo alternative splicing, being therefore widely recognized as major modulators of this process. Thus, the central hypothesis of the AS-ABA proposal is that posttranscriptional networks, SR protein nodes in particular, act as central coordinators of plant abiotic stress responses, namely by targeting ABA pathway components. Overview of the action: In view of the evidence linking AS to plant environmental responses and the recent findings by the Duque group implicating Arabidopsis SR proteins in stress responses regulated the ABA phytohormone, the overall objectives of this project are to uncover novel SR protein players in ABA-mediated plant stress tolerance and identify the splicing targets underlying their mode of action. Conclusions of the action: In this project, we identified the SR34a splicing factor as an important negative regulator of ABA-mediated stress responses during early seedling development. Indeed, using reverse genetic approaches, we showed that SR34a might regulate stress responses by decreasing sensitivity to ABA during seed germination and the post-germination transition from heterotrophic to autotrophic growth. In an attempt to address the molecular mode of action of SR34a, we first showed that this nuclear protein can bind RNA in vivo. Current ongoing work is being done in order to identify RNA targets and elucidate the exact molecular mechanisms by which SR34a controls those ABA-mediated stress responses. This project could have important socio-economic implications. Indeed, ABA-related stresses such as drought and high-salinity are severe environmental stresses that constitute the primary causes of crop losses worldwide and reduce average yields of most major crops by more than 50%. Thus, understanding how plants withstand environmental stresses successfully is a major objective in plant science. The control of plant stress responses by alternative splicing modulation is a relatively recent field of research holding much promise in providing new potential solutions for agricultural losses.

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