EFFECT OF PRIMING WITH GIBBERELLIN ON GERMINATION AND EXPRESSION OF GA BIOSYNTHESIS GENE OF TOMATO (SOLANUM LYCOPERSICUM L.) SEEDLINGS UNDER SALT STRESS

Seed germination is the initial step of plant development. Seed priming with salt enhances seed germination in tomato (Solanum lycopersicum L.); however, the molecular and physiological mechanisms underlying the enhancement of seed germination by priming remain to be elucidated. Tomato seeds were soaked for 24 hrs at 25 ºC in the dark in different concentrations of NaCl (NaCl-priming) or distilled water (hydro-priming) and different concentrations of gibberellin. In this study, we examined the expression of genes encoding gibberellic acid (GA) biosynthesis enzymes, including GA 20-oxidase (GA20ox), GA 3-oxidase (GA3ox) and GA4 (GA 3beta-hydroxylase). The germination percentage and germination rate of tomato seeds were increased after soaking with GA under NaCl stress. The expression profiles of GA biosynthesis genes were investigated with the semi-quantitative RT-PCR. Additionally, the expression levels of GA biosynthetic gene were higher in the NaCl-primed seeds than in the hydro-primed seeds. These results suggest that the observed effect of NaCl-priming on tomato seed germination is caused by an increase of the GA content via GA biosynthetic gene activation that helps tomato plant to tolerate salt stress. KEYWORDS: Seed Priming, Salt, Gibberellin, GA Biosynthesis Genes & Tomato