Liquid-liquid phase separation of RBGD2/4 is required for heat stress resistance in Arabidopsis

As sessile organisms, plants are highly sensitive to environmental stresses. In response to stresses, globally repressed translation initiation leads to stress granule (SG) formation. Protein liquid-liquid phase separation (LLPS) contributes to SG formation, but a direct link between protein LLPS and stress resistance has not yet been found in plants. Here, we report that two RNA-binding proteins, RBGD2 and RBGD4, function redundantly to improve heat resistance in Arabidopsis. RBGD2 and RBGD4 undergo LLPS in vitro and condense into heat-induced SGs in vivo via tyrosine residue array (TRA). Importantly, disrupting LLPS by mutating TRA abolishes RBGD2/4 condensation in SGs and impairs their protective function against heat stress (HS). Further study found that upon HS, the RBGD2/4 interaction network expands with additional SG proteins and heat-responsive mRNA. Our work shows a mechanistic basis that underlies protein LLPS in HS response in plants and suggests manipulation of protein LLPS as a general strategy to improve plant stress resistance. [Display omitted] •Two RNA binding proteins, RBGD2 and RBGD4, are required for heat stress in Arabidopsis•Heat induces liquid-liquid phase separation (LLPS) of RBGD2/4 in vitro and in vivo•Tyrosine residue arrays of RBGD2/4 are necessary for LLPS and plant heat resistance•RBGD2/4 organize specific proteins and transcripts into stress granules Zhu and Gu et al. discover two RNA binding proteins, RBGD2 and RBGD4, that phase separate in response to heat stress in plant cells and interact with specific heat-responsive transcripts. Their phase separation capacities, mediated by tyrosine residue arrays, are essential for their function in protecting plants from heat stress.