Аннотация:Interaction of dimeric 14-3-3 proteins with numerous phosphotargets regulates various physiological processes in plants, from flowering to transpiration and salt tolerance. Several genes express distinct 14-3-3 ‘isoforms’, particularly numerous in plants, but comparative studies of all 14-3-3 isoforms for a given organism have not been undertaken. Here we systematically investigated twelve 14-3-3 isoforms from the model plant Arabidopsis thaliana, uniformly capable of homodimerization at high protein concentration. We unexpectedly discovered that, at physiological protein concentrations, four isoforms representing a seemingly more ancestral, epsilon phylogenetic group (iota, mu, omicron, epsilon) demonstrate an outstanding monomerization propensity and enhanced surface hydrophobicity, which is uncharacteristic for eight non-epsilon isoforms (omega, phi, chi, psi, upsilon, nu, kappa, lambda). Further analysis revealed that dramatically lowered thermodynamic stabilities entail aggregation of the epsilon-group isoforms at near-physiological temperatures and provoke their proteolytic degradation. Structure-inspired single mutations in 14-3-3 iota could rescue non-epsilon behavior, thereby pinpointing key positions responsible for the phylogenetic demarcation. Combining two major demarcating positions (namely, 27th and 51st in omega) and multi-dimensional differences in biochemical properties identified here, we developed a predictor strongly supporting categorization of abundant 14-3-3 isoforms widely across plant groups, from Eudicots to Monocots, Gymnosperms and Lycophytes. In particular, our approach fully recapitulates the phylogenetic epsilon/non-epsilon demarcation in Eudicots and supports the presence of isoforms of both types in more primitive plant groups such as Selaginella, thereby refining solely sequence-based analysis in evolutionarily distant species and providing novel insights into the evolutionary history of the epsilon phylogenetic group.
