|Rajasekaran, Kanniah - Rajah|
Submitted to: Plant Biotechnology Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/12/2011
Publication Date: 4/2/2012
Citation: Baisakh, N., RamanaRao, M.V., Rajasekaran, K., Subudhi, P., Janda, J., Galbraith, D., Vernier, C., Pereira, A. 2012. Enhanced salt stress tolerance of rice plants expressing a vacuolar H+-ATPase subunit c1 (SaVHAc1) gene from the halophyte grass Spartina alterniflora Löisel. Plant Biotechnology Journal. 10:453-464. Interpretive Summary: Aflatoxin contamination of food and feed crops is often exacerbated when plants undergo physiological stress due to environmental factors. One of the environmental factors that induce physiological stress is salinity. Several salt tolerant grass species (called halophytes) regulate salt transport across membranes in their cells and organelles by using a key enzyme called vacuolar ATPase. We isolated a v-ATPase gene (SaVHAc1) from Spartina alterniflora or smooth cordgrass, a plant native to Louisiana coastal salt marshes and expressed it in transgenic tobacco and rice. The transgenic plants showed salt tolerance, and other physiological adaptations such as reduced stomatal density and closure of stomata to overcome stress. This study demonstrated that halophytes are not only useful to understand gene regulation mechanism for their natural adaptation to salinity, but also could be effectively used as donors for improving tolerance to salinity in several cultivated crops and also environmental stress factors. This research finding will be useful to other crop breeders and biotechnologists in developing new germplasm and crop varieties resistant to environmental stress due to salinity and drought.
Technical Abstract: The physiological role of a vacuolar ATPase subunit c1 (SaVHAc1) from a halophyte grass Spartina alterniflora was studied through its expression in rice. The SaVHAc1– expressing plants showed enhanced tolerance to salt stress than the wild-type plants, mainly through adjustments in early stage and preparatory physiological responses. In addition to the increased accumulation of its own transcript, SaVHAc1 expression led to increased accumulation of messages of other native genes in rice, especially those involved in cation transport and ABA signaling. The SaVHAc1–expressing plants maintained higher relative water content under salt stress through early stage closure of the leaf stoma and reduced stomata density. The increased K+/Na+ ratio and other cations established an ion homeostasis in SaVHAc1-expressing plants to protect the cytosol from toxic Na+ and thereby maintained higher chlorophyll retention than the WT plants under salt stress. Besides, the role of SaVHAc1 in cell wall expansion and maintenance of net photosynthesis was implicated by comparatively higher root and leaf growth, and yield of rice expressing SaVHAc1 over WT under salt stress. The study indicated that the genes contributing toward natural variation in grass halophytes could be effectively manipulated for improving salt tolerance of field crops within related taxa.