| The initiation of cotton lint and fuzz determined the yield and quality of fiber, it was emphasized on the mechanism of molecular development of lint, and ignored for the research on that of fuzz for a long time. The research on fuzz can help us understand the interaction mechanism of lint and fuzz and further illuminate the molecular characters of the cotton trichome development systematically, and get more benefits in cotton fiber yield and quality by research on cotton genetic resource. Recent improvement in cDNA microarray enable whole-genome expression analysis, network relationship analysis of genes expression and study of genes metabolic mechanism, which opens a new avenue for discover and select important genes. DPL971 and its lint-fuzzless mutant DPL972 in Gossypium arboreum L were used as materials in this study, and gene expression profiling was employed to select genes related to fuzz initiation, we also have deeply researched on a pair of homologous genes GaMYB23 and GaMYB23m to provide the information to understand the complex mechanism of fuzz fiber differentiation. The main results are as follows:(1) 1779 differentiation genes expressed between the fuzz mutant line DPL972 and its wild line DPL971 were selected in the early developing stage of -3DPA,0DPA,+3DPA,+5DPA,+7DPA by the filter arrays of cDNAs. Compared with the AraCyc database of Arabodopsis thaliana, 8 homologic genes of the leaf trichome in Arabodopsis were got. Five gene cDNA microarray results were vertified by RT-PCR, it revealed that there were some false positives existed in the cDNA microarray, Althought not all of the genes by RT-PCR can fit the cDNA microarray results well, the cDNA microarray results were believable in all.(2) RT-PCR and QRT-PCR was used to further confirm the gene expression patterns of GaMYB23 and its homologic gene GaMYB23m.The results revealed that the gene lower expressed in wild-type DPL971 than that in mutant line in the five stages, especially significant difference expression in +1DPA,+3DPA,+4DPA, and the gene was nearly inhibitted in +3DPA ovule of the wild-type. These results are consistent with the cDNA microarray well. The QRT-PCR result is also similar to cDNA microarray and significant difference expressed in 0DPA and +3DPA in QRT-PCR. These results implied this gene maybe relate to the fuzz differentiation.(3) The technique of RACE and Genome Walker were used to amplify the whole cDNA and DNA sequence, We obtained an open reading frame (ORF) of totally 621bp encoded a protein of 206 amino acid with molecular weight of 50.98 KDa protein. We found two bases were difference between GaMYB23 and GaMYB23m cloned from DPL971 and DPL972, and the nonpolar amino acid Glycine in the wild type was substituted by a polar amino acid Arginine in the mutant at conserved position 28 of GaMYB23. This indicated the conserved MYB domain may result in the change of GaMYB23.(4) From the cluster analysis of some proteins related to trichome development which contains MYB conserved domain, we found the relationship between GaMYB23 and GaMYB23m is the nearest, and the relationship between GaMYB23 and GL1,AtMYB23,AtWER,GaMYB109 is more near than that of GaMYB1~GaMYB6. It was clear that GL1,AtMYB23 and AtWER played a key roles in the development of trichomes in Arabodopsis, So we inferred that the protein GaMYB23 may also play important role in fuzz development.(5)To further understand the MYB conserved domain, we design primers to perform the Southern blot analysis, it revealed that there are no significant difference of GaMYB23 between the genome of DPL971 and DPL972, but many MYB domain copes in their Genome DNA, it can also implied that the conserved MYB domain may makes many roles in cotton development and metabolic process.
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