Fibers can be induced by the addition of auxin and gibberellic acid (Beasley and Ting 1974; Gialvalis and Seagull 2001; Kim and Triplett 2001), and the brassinosteroid brassinolide (BL) promotes fiber cell intiation as well as fiber cell elongation (Sun et al. 2005). Ethylene also promotes cell elongation by upregulating genes encoding sucrose
synthase, tubulin and expansin (Shi et al. 2006). In contrast, relatively little is known about the role of JA in fiber development. In this study, an expressed sequence tag (EST; GenBank accession no. ES792958) exhibiting significant expression differences during fiber initiation stages in lintless-fuzzless XinWX and linted-fuzzless XinFLM isogenic lines was screened using 28K cotton genome array hybridization. By using the EST to search the Gossypium EST database (http://www.ncbi.nlm.nih.gov/), we cloned and characterized a cotton AOC gene. In addition, qRT-PCR and association analysis showed that the AOC played an important role in cotton fiber development, especially in econdary cell wall thickening. JA therefore appears to function in the signaling pathways regulating fiber development in cotton.