Studies On Biological Function Of The Cotton MYB Transcription Factor GhMS3

Cotton is the most important crop for natural fiber production. Cotton fibre, which develop from single epidermal cells of outer integument, is a good model for the cell differentiation research. With the development of textile industry, the new textile technology puts increasing demand on high-quality of cotton fibre. Therefore, cloning the genes involved in cotton fibre development and characterizing their functions not only have the potential practical value, but also provide theoretical basis for epidermal cell differentiation studies in plants.Arabidopsis epidermal cells are widely used as the model for cell differentiation. It is well known that TTG1/GL3/GL1 protein complex activates the expression of downstream gene GL2, ultimately leading such epidermal cells to differentiating into trichomes. If GL1 is replaced by negative regulatory factors, such as TCL1, the protein complex cannot activate GL2 expression and this leads to a failure of such epidermal cells to differentiate into trichomes. During root epidermal cell differentiation, the cells in which the WER/GL3/TTG1 protein complex activates the expression of GL2 differentiate into hairless cells; whereas the cells in which GL2 is not expressed due to the formation of CPC/TTG1/GL3 protein complex develop into root hair cells.Cotton fibre is also known as seed trichomes. The initiation and development of cotton fiber has a mechanism similar to the differentiation and development of trichomes and root hairs. Therefore, the understanding of Arabidopsis trichome and root hair differentiation has shed light on cotton fiber development mechanisms. Not surprisingly, the studies on cotton fiber development are far behind that on epidermal cell differentiation in Arabidopsis. So far, only a few genes involved in fiber development have been isolated, but their functions remain largely unknown. Some MYB genes such as GhMYB1-6, GhMYB7, GhMYB9, GhMYB25, GhMYB109 and GaMYB2 have been isolated from wild cotton. Owing to the relative difficulty in cotton genetic transformation, the functional analysis of the isolate MYB genes has mainly been carried out in yeast, Arabidopsis, or tobacco. GhMYB1 (CotMYBA ) overexpression in tobacco led to a significant increace in trichomes of cotyledons and other organs; Constitutive overexpression of GhMYB25 in transgenic tobacco resulted in an increase in branched longstalked leaf trichomes.GhMS3 that was expressed specifically in -3DPA(day post anthesis)ovule of fuzzless cotton mutant was isolated from GZnn, by differential display, RACE(rapid amplification of the cDNA ends)and genome walking. Bioinformatics methods were used to analyze the DNA and the encoded amino acid sequence. And the results showed that GhMS3 was a R2R3 MYB transcription factor gene. Yeast one-hybrid assay showed that the C terminus of GhMS3 had strong activation ability compared to the full length of polypeptide. GUS histochemiscal staining revealed a strong expression in trichomes, root hairs, and actively dividing cells in PGhMS3:GUS transgenic tobacco plants. GhMS3 protein could not be detected, albeit the highly aboundant transcripts of GhMS3 were detected in P35S:GhMS3 transgenic tobacco plants. Such R2R3-type MYB transcription factor GhMS3 isolated from fuzzless cotton mutant has not been reported yet. In this study, we just investigated the function of GhMS3 in yeast and tobacco, but a further function analysis in cotton is carried on..