Metabolic Responses of Transgenic Creeping Bentgrass for a Cytokinin Biosynthesis Gene to Drought Stress.

Drought stress is a widespread abiotic plant disease that causes a decline in plant growth and vigor.  Creeping bentgrass (Agrostis stolonifera L.)  is a turfgrass species that has only moderate drought tolerance and its quality as a functional turf declines rapidly due to drought.  Many physiological changes occur due to a reduction in plant water status including a loss of leaf relative water content, photochemical efficiency (FvFm), chlorophyll content, hormone content, and generation of reactive oxygen species. Relatively little information compared to other drought responsive hormones such as ABA is available about the role of plant cytokinins in drought tolerance of turfgrass species.  This study aimed to analyze the drought tolerance mechanisms influenced by the effects of an isopentyltransferase (ipt) transgene that increases endogenous cytokinin content, controlled by a senescence activated promoter (Sag12), on creeping bentgrass drought tolerance. Transgenic and empty vector control lines were grown in a 1:1 sand soil mix in a growth chamber and were exposed to drought stress until soil moisture reached 5%. Plants were then re-watered for analysis of recuperative potential. Results showed that transgenic creeping bentgrass maintained higher leaf relative water content, osmotic adjustment, chlorophyll content, photosynthetic efficiency, enhanced activity of antioxidant enzymes and lower levels of electrolyte leakage during drought stress.  The effects of the transgene on differential protein and RNA expression during drought stress will also be discussed.