Genetic and Morpho-Physiological Differences among Transgenic and No-Transgenic Cotton Cultivars.

Three carbon-chain extension genes associated with fatty acid synthesis in upland cotton (), namely , , and , play important roles in oil accumulation in cotton seeds. In the present study, these three genes were cloned and characterized. The expression patterns of , , and in the high seed oil content cultivars 10H1014 and 10H1041 differed somewhat compared with those of 10H1007 and 2074B with low seed oil content at different stages of seed development. showed all three cultivars showed higher transcript levels than that of 2074B at 10-, 40-, and 45-days post anthesis (DPA). The expression pattern of showed a lower transcript level than that of 2074B at both 10 and 30 DPA but a higher transcript level than that of 2074B at 40 DPA. showed a lower transcript level than that of 2074B at both 15 and 30 DPA. The highest transcript levels of and were detected at 15 DPA in 10H1007, 10H1014, and 10H1041 compared with 2074B. From 5 to 45 DPA cotton seed, the oil content accumulated continuously in the developing seed. Oil accumulation reached a peak between 40 DPA and 45 DPA and slightly decreased in mature seed. In addition, and showed different expression patterns in fiber and ovule development processes, in which they showed high expression levels at 20 DPA during the fiber elongation stage, but their expression level peaked at 15 DPA during ovule development processes. These two genes showed the lowest expression levels at the late seed maturation stage, while showed a peak of 10 DPA in fiber development. Compared to 2074B, the oil contents of and overexpression lines increased 1.05~1.08 folds. These results indicated that , , and were involved in both seed oil synthesis and fiber elongation with dual biological functions in cotton.