Silencing of -A GSK3/SHAGGY-Like Kinase-Enhances Barley ( L.) Growth in Normal and in Salt Stress Conditions.

Glycogen synthase kinase 3 (GSK3) is a highly conserved kinase present in all eukaryotes and functions as a key regulator of a wide range of physiological and developmental processes. The kinase, known in land plants as GSK3/SHAGGY-like kinase (GSK), is a key player in the brassinosteroid (BR) signaling pathway. The genes, through the BRs, affect diverse developmental processes and modulate responses to environmental factors. In this work, we describe functional analysis of , which is one of the -like orthologs in barley. The RNAi-mediated silencing of the target gene was associated with modified expression of its paralogs , , , and in plants grown in normal and in salt stress conditions. Low nucleotide similarity between the silencing fragment and barley genes and the presence of BR-dependent transcription factors' binding sites in promoter regions of barley and rice genes imply an innate mechanism responsible for co-regulation of the genes. The results of the leaf inclination assay indicated that silencing of and the changes of paralogs enhanced the BR-dependent signaling in the plants. The strongest phenotype of transgenic lines with downregulated and paralogs had greater biomass of the seedlings grown in normal conditions and salt stress as well as elevated kernel weight of plants grown in normal conditions. Both traits showed a strong negative correlation with the transcript level of the target gene and the paralogs. The characteristics of barley lines with silenced expression of are compatible with the expected phenotypes of plants with enhanced BR signaling. The results show that manipulation of the GSK-encoding genes provides data to explore their biological functions and confirm it as a feasible strategy to generate plants with improved agricultural traits.