Transgenic Cotton Lines Over-Expressing Delta-12 Fatty Acid Desaturase (FAD2-4) Exhibit Improved Seedling Vigor Under Cool Temperatures

Chilling sensitive species, like cotton, tend to have poor membrane fluidity at low temperatures, resulting in a number of negative physiological consequences. Membrane fluidity and tolerance to cool, early season temperatures could potentially be improved in cotton if fatty acids were less saturated during the seedling stage. Consequently, the objective of the current study was to assess the response of seedling vigor three weeks after planting under cool (20/15C) and optimal (30/20C) day/night temperature conditions for one parental line (Coker 312) and 6 different transgenic cotton lines overexpressing a cotton isoform of the delta-12 fatty acid desaturase. Our findings indicate that multiple FAD2-4 overexpressing lines assessed demonstrated promise for improving seedling vigor under cool conditions, relative to Coker 312. Specifically, L4 demonstrated greater seedling vigor than the parental line in all parameters measured under the 20/15C temperature regime. Importantly, with the exception of L3 for plant fresh weight, all FAD2-4 transgenic lines perform similarly to Coker 312 under optimal temperature conditions, indicating no negative impacts of fatty acid desaturase over expression under optimal conditions. Thus, fatty acid desaturation appears to be a promising approach for improving seedling vigor under cool temperature conditions while not negatively impacting performance under optimal growth temperatures. The genotypes assessed in the controlled environment study are currently being evaluated in the field using planting date to expose all lines to cool early-season temperatures.