Functional analysis of GbML1 during cotton fiber iniation

Functional Genomics

oral

zuo, kaijing ; zhang, Fei ; Tang, kexuan

zuo, kaijing

The regulatory mechanism of cotton fiber development is always the key part of cotton research. However, this process is not fully understtod. In this research, we chose the high-quality fiber bearing cultivar, Gossypium barbadense, as the main material to uncover the mechanism during fiber development at early stage. By combination of the effects in gene cloning, evolution study, expression analysis, protein-DNA binding, protein-protein interaction and functional study by transgenic plants, we achieaved the results as follows; A new HD-Zip IV family member, designated as GbML1, was cloned from early tage ovules by RACE technique. GbML1 could form homodimers by its ZLZ domain and this dimmer formation is critical for its binding to DNA. GbML1 could pecifically bind to L1 box by its HD domain. The expression of GbML1 and GbMYB25 was similar during cotton ovule development and both protein could be ocalized into nucleus. Moreover, GbML1 could interact with the C terminal part of GbMYB25 by its START-SAD domain and the three dimentional structure of START domain was important for the binding. Though GbML1 itself was a weak ctivator, but the C2 domain of GbMYB25 had strong activation activity. Thus the complex formed by GbML1 and GbMYB25 both had the DNA specific binding activity and transcriptional activation activity. This complex could bind to the promoters of fiber specific genes and then activated their expression. Overexpression of GbML1 in Arabidopsis not only increased the trichome number in the leaf and stem epidermis, but also activated seed fiber formation in Arabidopsis, which supported that GbML1 was a key regulator in cotton fiber differentiation and development.