ИСТИНА

Plant growth and development, as well as stress tolerance, is controlled by phytohormones and protein regulators under diverse environmental conditions. Universal stress proteins (USPs) were first discovered in bacteria to play an important role in survival under various stresses. In plants, proteins containing USP domain with the specific structure of nucleotide-binding Rossmann-like fold were found, but not all of USPs able to bind nucleotides. Several USP plant homologues are expressed in response to phytohormones and abiotic stresses. However, biological function of plant USPs still remains unknown. We characterized the transgenic plants with low expression of At3g58450 gene encoding a homologue of the USP family. This protein shared identity to Arabidopsis thaliana USP-proteins however does not extend through all the known secondary structure elements of USP domain. The transgenic plants demonstrated prolonged vegetative phase and delayed flowering partially reversed by gibberellins (GA) treatment. Consistent with this, mutants showed reduced content of bioactive GAs (GA1 and GA3) and altered expression of GA metabolic pathway genes (GA-dioxygenases). These results show the involvement of AT3G58450 protein in regulation of gibberellins-mediated growth responses. On the other hand, gene expression analysis demonstrated At3g58450 gene to be induced in response to abscisic acid (ABA) treatment and to be suppressed indirectly by GA. These results may indicate the involvement of AT3G58450 protein not only in abiotic stress responses as universal stress protein, but in regulation of GA-dependent processes of growth and development in normal conditions. We suggest this protein to play possible role in regulation of growth and development by involvement in crosstalk between GA and other plant hormones.