Ectopic expression of two AREB/ABF orthologs increases drought tolerance in cotton (Gossypium hirsutum).

Plants have evolved complex molecular, cellular and physiological mechanisms to respond to environmental stressors. Because of the inherent complexity of this response, genetic manipulation to substantially improve water deficit tolerance, particularly in agricultural crops, has been largely unsuccessful, as the improvements are frequently accompanied by slower growth and delayed reproduction. Here, we ectopically express two abiotic stress-responsive bZIP AREB/ABF transcription factor orthologs, Arabidopsis ABF3 and Gossypium hirsutum ABF2D, in G.

Functional analysis of cotton orthologs of GA signal transduction factors GID1 and SLR1.

Gibberellic acid (GA) is both necessary and sufficient to promote fiber elongation in cultured fertilized ovules of the upland cotton variety Coker 312. This is likely due to the temporal and spatial regulation of GA biosynthesis, perception, and subsequent signal transduction that leads to alterations in gene expression and morphology. Our results indicate that the initiation of fiber elongation by the application of GA to cultured ovules corresponds with increased expression of genes that encode xyloglucan endotransglycosylase/hydrolase (XTH) and expansin (EXP) that are involved in promoting cell elongation.

Brassinosteroid regulates fiber development on cultured cotton ovules.

Our current understanding of the role of phytohormones in the development of cotton fibers is derived largely from an amenable culture system in which cotton ovules, collected on the day of anthesis, are floated on liquid media. Under these conditions, supplemental auxin and gibberellin were found to promote fiber initiation and elongation. More recently, addition of low concentrations of the brassinosteroid brassinolide (BL) were also found to promote fiber elongation while a brassinosteroid biosynthesis inhibitor brassinazole2001 (Brz) inhibited fiber development.