A comparative analysis ofafuzzless-lintless mutant ofGossypium hirsutum L. cv. Xu-142

Afuzzless-lintless (fl) seed mutant ofGossypium hirsutum L. cv. Xu-142 was investigated to study cotton fiber development. Scanning electron microscopy revealed that fiber initials were virtually absent fromfl ovules. RT-PCR analysis showed that the steady-state levels of transcripts of the fiber-specificE6 andExpansin genes were high in wild type (WT) ovules during the fiber initiation and elongation stages, and peaked around 15 days post anthesis (DPA), but only a trace amount of these transcripts was detectable infl ovules of all developmental stages investigated.CotmybA, a member of theMyb family, exhibited a clear expression in developing WT ovules, but the expression was abnormal infl ovules. Application of GA(3), or GA(3) plus IAA, to the culture medium rescuedin vitro fiber initiation and growth offl ovules only partially. In addition, transcription ofE6 andExpansin genes ofin vitro cultured WT andfl ovules responded similarly to exogenous hormones. The hormones had less effect onCotmybA transcription in ovules culturedin vitro, and again the WT andfl ovules showed a similar expression. These results suggest that the abnormal or extremely low level of expression ofE6, Expansin andCotmybA genes in developingfl seeds is related to the absence of seed-hairs, and the mechanism underlying needs further investigation.