Physiological and molecular strategies for salt tolerance in Thellungiella halophila, a close relative of Arabidopsis thaliana
Salt stress is one of the most threatening environmental stresses reducing the global food production. Understanding mechanisms of salt tolerance in halophytic plants is a requirement for developing crop species with increased salt tolerance. This study focused on investigating ion transplant features in a halophytic relative of Arabidopsis, both at physiological and transcriptional level. A comparative approach was adopted in this study using the glycophytic model plant Arabidopsis thaliana, and its halophytic close relative, Thellungiella halophila. Net ion uptake and unidirectional Na fluxes during salt stress were analyzed in the two species. Furthermore, transcriptional profiles of ion transporters under control and high-salt conditions were compared between the two species. The considerable amount of data produced in this study provide important information for future physiological and molecular studies of both Arabidopsis and Thellungiella. The main results can be summarized thus: 1. After salt stress Thellungiella accumulates less Na in the shoots than Arabidopsis. Net uptake of Na into both roots and shoots was slower in Thellungiella than in Arabidopsis. 2. Lower unidirectional Na influx into root cells is the main reason for the lower Na accumulation in Thellungiella than in Arabidopsis. 3. Voltage-independent cation channels (VICs) are likely to be the Na uptake pathway in both Thellungiella and Arabidopsis. 4. Microarray analysis showed that after salt stress both species showed a tendency to reduce Na uptake by decreasing the expression of possible pathways for Na influx. However, transcriptional control of putative Na transporters occurred in Arabidopsis in the shoots, whereas it occurred in Thellungiella in the roots. 5. CNGC8 is a likely candidate for a Na uptake pathway in both Arabidopsis and Thellungiella. Transcript levels of CNGC8 decreased during salt stress in Thellungiella roots and Arabidopsis shoots.