Advances in cotton biotechnology and gene discovery are making the selection and manipulation of fiber genes for the improvement of yield and fiber quality a reachable goal . To test the potential for altering fiber properties, the expression of expansin, a cell wall enzyme involved in fiber elongation, was altered in transgenic cotton plants. Four different gene constructs were assembled, in which the expansin gene was cloned in the sense or antisense (RNAi) orientation under the control of two different promoters - a cotton promoter or the CaMV 35S constitutive promoter. The genes were introduced into G. hirsutum L. cv. Coker-312 by Agrobacterium-mediated transformation. Variations in the number and density of leaf and stem hairs (trichomes), flower morphology (anthers and stigma), leaf size and shape, and fiber quality were observed relative to control plants, depending on the gene construct. Transgenic cotton plants containing the 35S::expansin gene construct exhibited increased fiber strength, fiber tenacity and fiber weight/seed (yield).
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