Molecular and functional characterization of the durum wheat TdRL1, a member of the conserved Poaceae RSS1-like family that exhibits features of intrinsically disordered proteins and confers stress tolerance in yeast.

Because of their fixed lifestyle, plants must acclimate to environmental changes by orchestrating several responses ranging from protective measures to growth control. Growth arrest is observed upon abiotic stress and can cause penalties to plant production. But, the molecular interface between stress perception and cell cycle control is poorly understood. The rice protein RSS1 is required at G1/S transition ensuring normal dividing activity of proliferative cells during salt stress. The role of RSS1 in meristem maintenance together with its flexible protein structure implies its key function as molecular integrator of stress signaling for cell cycle control. To study further the relevance of RSS1 and its related proteins in cereals, we isolated the durum wheat homolog, TdRL1, from Tunisian durum wheat varieties and extended our analyses to RSS1-like proteins from Poaceae. Our results show that the primary sequences of TdRL1 and the Graminae RSS1-like family members are highly conserved. In silico analyses predict that TdRL1 and other RSS1-like proteins share flexible 3-D structures and have features of intrinsically disordered/unstructured proteins (IDP). The disordered structure of TdRL1 is well illustrated by an electrophoretical mobility shift of the purified protein. Moreover, heterologous expression of TdRL1 in yeast improves its tolerance to salt and heat stresses strongly suggesting its involvement in abiotic stress tolerance mechanisms. Such finding adds new knowledge to our understanding of how IDPs may contribute as central molecular integrators of stress signaling into improving plant tolerance to abiotic stresses.