Trichostatin and dimethyl sulfoxide enhance somatic embryogenesis from root apices of spinach

Abstract

Epigenetic modifications of chromatin play a pivotal role in regulation of expression of genes involved in somatic embryo (SE) induction. Hence, the compounds which affect DNA-histone interaction may trigger somatic embryogenesis. Trichostatin (TSA) is a potent inhibitor of histone deacetylases, whose activity leads to increased histone acetylation, thereby affecting gene expression. To explore epigenetic control of SE regeneration from root apices (1 cm) of spinach seedlings, the explants were cultivated on media supplemented with 0, 0.1, 0.5, 1 or 5 μM TSA + 0, 1, 10 or 20 μM α naphthaleneacetic acid (NAA) + 0 or 5 μM gibberellic acid (GA3). The explants were exposed to TSA for 1, 7 or 14 days, and subsequently subcultivated on TSA free medium of the same composition. TSA was dissolved in dimethyl sulfoxide (DMSO), whose final concentration in all media, including TSA-free controls, was 0.05%. TSA was not sufficient to induce SEs either alone or in combination with NAA or GA3. SE regeneration was observed only from the explants cultivated on media supplemented with 10 or 20 μM NAA + 5 μM GA3. In both combinations, TSA promoted somatic embryogenesis, but longer TSA treatment was needed with 10 μM NAA than with 20 μMNAA for efficient SE induction. The highest embryogenic response was attained with 0.1-0.5 μM TSA. DMSO also significantly improved SE induction, probably by enhancing NAA and GA3 intake into the plant cells. The results indicate a significant role of epigenetic control in SE induction in spinach.