Identification of dehydrin protein complexes in vivo reveals functional interactions of LEA5 with OSCA3, PIP2B and PLDα1 in plant water-deficit stress

Climate change and especially the concomitant increasing frequency of drought and salinity induced water-deficit stresses, is a major limiting factor of plant growth and crop productivity worldwide. Understanding the adaptive responses of plants to water-deficit stress has therefore become a central challenge in plant biotechnology. Considerable evidence indicates that late embryogenesis abundant (LEA) proteins contribute to water-deficit stress tolerance and the stabilization of metabolic enzymes, yet the molecular basis of these responses remains unknown. To date, limited direct evidence for specific in vivo interactions between LEA proteins and their molecular targets has been reported. Here, we identify for the first time the native in vivo interactome of three Arabidopsis dehydrin LEA proteins - LEA4 (COR47), LEA5 (ERD10), and LEA10 (ERD14) - expressed under their own promoters and in response to salt stress. Our results show that LEA4, LEA5, and LEA10 dehydrins interact with each other, and share six common candidate protein interactors, suggesting that they form a core protein complex in salt stress conditions. We confirmed the direct protein-protein interaction between LEA5 with LEA4, LEA10, OSCA3, PLD1, PIP2B and OST1/AHA1 at the biochemical level. Phenotypic analyses of loss-of-function genetic mutants revealed that the interactions of LEA5 with OSCA3 and PIP2B promote seed germination under salt stress. LEA5 interaction with PLD1 promotes root growth under salt stress, while its interaction with PIP2B enhances root growth under osmotic stress, indicating distinct stress-specific functional roles for each interaction. In conclusion, this study identifies the native in vivo interactions of three dehydrin proteins, while uncovering the functional relevance of these interactions under salt and osmotic stress conditions, thus providing novel mechanistic insights into the role of LEA proteins in water-deficit stress adaptation.