Submitted to: Journal of Plant Physiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/12/2007
Publication Date: 4/18/2008
Citation: Dombrowski, J.E., Baldwin, J.C., Martin, R.C. 2008. Cloning and characterization of a salt stress-inducible small GTPase gene from the model grass species Lolium temulentum. Journal of Plant Physiology.165:651-661. Interpretive Summary: Soil salinity is one of the major abiotic stresses responsible for reduced persistence, yield and biomass accumulation in many crops, including forage. Consequently, it is of great importance to develop a better understanding of salt tolerance in forage species. Forage grass species are generally polymorphic, obligate out-crossers that are self-incompatible. Because of their high genetic diversity the mechanisms of salt tolerance are poorly understood. Our previous analysis identified three genes believed to be involved in salt stress tolerance in the model grass species Lolium temulentum. These genes were analyzed for their response to salinity as well as their responses to seven different forms of abiotic stress in L. temulentum plants. A gene encoding for a small GTPase, a signaling protein and a stress tolerance gene involved in production of osmoprotectants in plants, displayed expression patterns that indicate a role in dehydration stress tolerance. In contrast, a gene encoding for an integral membrane protein, was found to be up-regulated in response to all stresses tested and has utility as a general stress marker in grass plants. The results described in the manuscript provide a valuable first step towards elucidating the role of water-stress tolerance genes in forage and turf grasses.
Technical Abstract: A gene encoding a small GTP binding protein (smGTP) related to the Rab2 gene family of GTPases was identified during the analysis of a salt stress suppression subtractive hybridization (SSH) expression library from the model grass species Lolium temulentum L. (Darnel ryegrass). The smGTP gene was found to have a low level constitutive expression and was strongly induced by salt stress in root, crown and leaf tissues. The expression pattern of the smGTP gene was compared against two additional stress genes identified in the SSH expression library, the well characterized dehydration stress tolerance gene, delta 1-pyrroline-5-carboxylate synthetase (P5CS) encoding for a key enzyme in proline biosynthesis, and the cold response gene COR413. The genes were analyzed for their response to salinity as well as their responses to seven different forms of abiotic stress in L. temulentum plants. The smGTP gene displayed an expression pattern similar to the P5CS gene suggesting a role in dehydration stress. In contrast, the COR413 gene was found to be up-regulated in response to all stresses tested and has utility as a general stress marker in grass plants.