Identification Of An ABA-insensitive Thellungiella Mutant And Cloning Of The Corresponding Gene

The plant hormone ABA (Abscisic acid) plays a central role in many aspects of stress responses as well as seed dormancy, germination, later root development and flowering. ABA can be synthesized and accumulated quickly when plants are facing salt and drought stress, which consequently induces the expression of the stress responsive genes. Thellungiella halophila (salt cress) is an annual crucifer with high sequence identity (average 92%) compared to Arabidopsis. However, Thellungiella can survive even higher salinity (500mM NaCl) and lower temperature (-15℃). Interestingly, the seed germination of Thellungiella is more sensitive to salinity and ABA compared to that of Arabidopsis. To understand the mechanism of Thellungiella adaptation to the abiotic stress, we screened the T-DNA insertion mutant pools of Thellungiella by germinating the seeds on media containing 2μM ABA. A mutant that showed insensitivity to ABA during germination was isolated and the mutated gene was identified by TAIL-PCR. The mutated gene was a member of the short-chain dehydrogenase/reductase gene (SDR) family and was named BRT. The Thellungiella BRT gene was then cloned, and its sequence was compared with its ortholog in Arabidopsis. The function of BRT gene in Thellungiella germination and the possibly involved pathway were also discussed.