MSc Exit Seminar – Malaika Gomes (Nambara Lab)

Abstract

After-ripening (AR) is a process promoting seed germination, which occurs in the dry seed when storage time is extended. AR increases the seed’s response to environmental signals such as nitrate, which then regulates expression of AR-regulated genes upon imbibition. However, this mechanism is unknown. In this study, the role of reactive oxygen species (ROS) in expression of AR-regulated genes was investigated. Using the promoter:β-glucuronidase reporter system, AR was shown to alter spatial expression patterns of CHOTTO1 (CHO1), an AR repressor, enhancing its expression in the vasculature. Interestingly, AR seeds of the cho1 mutant enhanced superoxide accumulation in the vasculature. Pharmacological experiments suggest H₂O₂ decreases expression of CHO1, while increases expression of CYP707A2, another AR-regulated gene. Furthermore, H₂O₂ application increases nitric oxide release, but nitrate inhibits it, through NIN-Like Protein8, involved in nitrate signalling. These findings suggest ROS form a regulatory loop to regulate expression of AR-regulated genes, CHO1 and CYP707A2.