Differential expression profile of DREB2 subfamily transcription factor genes in the dynamics of salt stress and post-stress recovery in tomato plants

In response to stress, epigenetic modifications occur in the plant genome, which together form a stress memory that can be inherited and increases the efficiency of the plant's defense response to repeated stress events. Genes whose expression becomes the target of epigenetic modifications serve as biomarkers of stress memory. Their characteristic features are considered to be an expression profile that differs between responses to primary and repeated stress events, as well as long-term retention of changes after the stress is canceled. Tomato (Solanum lycopersicum L.) is an important vegetable crop whose yield decreases with soil salinity. Genes induced by salt stress include genes encoding transcription factors of the DREB2 (DEHYDRATION-RESPONSIVE ELEMENT-BINDING PROTEIN 2) subfamily. In this work, we evaluated the SlDREB2 genes of tomato as possible marker genes of salt stress memory. The expression of the genes SlDREB16, 20, 22, 24, 43, 44 and 46 was determined in the leaves of two plant varieties (Gnom, Otradnyi) with different degrees of salt tolerance in response to 24 h of NaCl exposure and in the dynamics of a long-term (14 days) post-stress recovery period. Significant genotype-specific fluctuations in the levels of gene transcripts were revealed both in the control and in the stressed plants. It was shown that during the long-term memory phase, gene expression returns to the control values either temporarily (SlDREB24, 44 and 46 in the moderately resistant Gnom variety after 7 days; after 14 days, the expression changed again) or slowly (SlDREB16 and 43 in the highly resistant Otradnyi variety after 14 days of recovery). Only two genes (SlDREB22 and 46) showed a similar between varieties pattern of expression fluctuations in the dynamics of stress and recovery, and the SlDREB20 gene was not expressed in either the control or the experiment. The data obtained suggest that the SlDREB2 subfamily genes (except SlDREB20) are involved in the response of S. lycopersicum to salt stress in a genotype-specific manner and can serve as markers of stress memory linked to the epigenetic regulation of tomato adaptation to salt stress. The SlDREB16, 28, 43 and 44 genes may contribute to the determination of differences in the mechanism of regulation of plant response to salt stress between salt-tolerant genotypes of S. lycopersicum. The obtained results can form the basis for further studies of the role of SlDREB2 genes in the epigenetic regulation of tomato plant adaptation to salt stress, which can be used in breeding salt-tolerant varieties.

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