Ethylene Synthesis and Relative Gene Expression In Cotton Under Drought Stress.

Literature has diverging opinions on water deficit effects over ethylene synthesis. Experiments reporting ethylene synthesis increase due to water deficit stress used detached plant parts subjected to quick drying. On contrary, ethylene emission studies which evaluated whole plants exposed to a gradual drying out period did not show increase in ethylene levels. The objectives were to determine if ethylene synthesis rate and related genes expression would be modified by water deficit stress in plants; and if 1-MCP (ethylene antagonist) would have any effect on ethylene production and gene expression. Greenhouse study was conducted during two years as 2x2 factorial design a in split-block arrangement with five replications. Treatments were two 1-MCP rates (0 and 1,000 ppb) during 14 hours overnight and then were subject to two water regimes (control and stressed). At 1, 5, 7, 9, 11, and 13 DAT, ethylene production of stressed plants never exceeded those of Control plants. As the ψ_w became more negative the ethylene production rate was reduced among stressed plants independent of 1-MCP treatments, with a truly linear relationship between ψ_w and ethylene evident after 7 DAT. ACS6 and ACO2 expression, which respectively encode for enzymes that convert SAM to ACC and ACC to ethylene, most of times showed identical trend that gave support to ethylene synthesis data. GDSL-motif lipase gene, encodes for multifunctional properties enzymes, showed its potential as drought-responsive gene. Results indicated that water deficit stress caused a decrease in ethylene synthesis, which was validated in part by gene expression.