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

Abstract

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.

Keywords: RNA metabolism; RNA-binding proteins; post-transcriptional gene regulation; stress granules (SGs); stress response.

FIGURE 1

Model depicting the regulatory functions of the typical RNA-binding proteins in plant adaptation to abiotic stress. Environmental stress caused by salt, drought, cold, heat, hypoxia, flooding or oxidative conditions may induce or repress the expression of relevant RBPs. During the response, RBPs may act in a ABA-dependent or independent pathway to regulate gene expression and play various roles in RNA metabolism including RNA processing and alternative splicing in the nucleus, nuclear export of mRNAs, mRNA degradation via processing bodies, mRNA storage in stress granules, and translational control in the cytoplasm. Some RBPs may also function as RNA chaperones to assist RNA folding and structure remodeling. Nuclear-encoded RBPs may also be targeted to chloroplasts or mitochondria and participate in intron splicing, rRNAs processing and/or translation of plastid mRNAs, processes critical for organellar biogenesis and function during plant adaptation to stress. Examples of RBPs that are involved in each cellular process are shown in the model. More detailed information can be found in Table 1 and in the main text.