Overexpression Of Rice Osgai In Rice And Tobacco Modulates Gibberellic Acid-Dependent Responses

Gibberellin, or gibberellic acid (GA), is a crucial phytohormone for its role in overall plant growth and development, particularly in the regulation of plant height. Among the GA-signaling mutants, the gai (GA insensitive) gene has been well studied in Arabidopsis [Arabidopsis thaliana (L.) Heynh.] system. The wild-type GAI, being a DELLA-family protein, acts as a nuclear-localized GA-signaling repressor that restrains the expression of other genes associated with GA-induced growth processes. Here we document alteration in GA-dependent multiple responses obtained through overexpression and expression of the rice (Oryza sativa L.) wild-type GAI (OsGAI) gene in the endogenous (rice) and heterologous (tobacco [Nicotiana tabacum L.]) plant systems, respectively. In both cases, the transgenic lines were found to have significantly reduced plant height, decreased seed alpha-amylase activity, reduced early seedling growth, a higher level of anthocyanin pigmentation, and reduced stem cell-wall lignifications. Leaf chlorophyll content was found to be increased in transgenic rice but decreased in transgenic tobacco lines. The reduced lignification in transgenic tobacco was observed to be reversible on exogenous GA application and correlated to the hypersensitivity toward oxidative stress. Findings of the present research advance our understanding on the complex interplay between GAI and interacting molecules responsible for several physiological processes in plant systems.