Beside as precursors of BRs biosynthesis, more and more evidences supported that phytosterols play an important role in plant growth and development. To investigate the effects of phytosterols on the fiber development of upland cotton (Gossypium hirsutum L.) and the molecular base of sterol regulating cotton fiber growth, a homologue of HYDRA1 was cloned from upland cotton (cv. Xuzhou 142) by screening cotton fiber EST database and contigging the candidate ESTs. The GhHYDRA1 encoded a polypeptide of 218 amino acid residues and the deduced amino acid sequences had high homology with the members of HYDRA1 in Populus trichocarpa, Solanum tuberosum, and Arabidopsis thaliana. Moreover, GhHYDRA1 had comparable transmembrane regions to AtHYDRA1 in sequence, length, order, and spacing, except for a C-terminal polylysine cluster. Quantitative real-time RT-PCR analysis revealed that the higher expression levels of GhHYDRA1 gene were detected in 6 to 12 DPA (days post anthesis) fibers, while the lower levels were observed in 0 DPA ovule (with fibers) and 16 to 18 DPA fibers. These results indicated that GhHYDRA1 is the homologue of HYDRA1 gene and plays a crucial role in fiber elongation. Furthermore, auxin and BL up-regulated the expression level of GhHYDRA1 while ABA and KT down-regulated the expression level of GhHYDRA1 in cotton ovule and fiber growth. The result suggested that phytosterols play a role in the interaction of plant hormones.
ZANG Zhen-le HU Ming-yu LI Xian-bi CHEN Kui-jun LIAO Peng XIAO Yue-hua HOU Lei PEI Yanand LUO Ming
