Study On The Role Of A Cotton(Gossypium Hirsutum) MYB Transcription Factor In Fiber Secondary Cell Wall Thickening

Cotton is an important cash crop in the world.Cotton fiber can not only be used as textile material in textile industry,but also play an important role in agriculture and food industry.Cotton fiber quality is very important for textile industry and related industries.Previous studies have shown that secondary wall development of cotton fiber cells mainly determines the strength of cotton fiber.Secondary walls of cotton fiber cells are mainly composed of cellulose,which is mainly regulated by NAC and MYB transcription factors and their downstream transcription factors.In the previous study,an R2R3-MYB transcription factor GhMYBL1 was isolated and identified in this laboratory.Overexpression of GhMYBLl in arabidopsis thaliana revealed ectopic deposition of secondary wall components in transgenic plants,and the expression of secondary wall related genes such as CesA4/7/8 was activated.This paper mainly studied the function of GhMYBL1 in cotton.After obtaining the transgenic cotton material of GhMYBL1,the phenotype of transgenic cotton was analyzed,and the molecular mechanism of GhMYBL1 regulating the secondary wall development of fiber cells was discussed.The research results obtained in this paper are as follows:1.GhMYBLl gene is involved in regulating secondary wall development of cotton fiber cellsIn order to study the function of GhMYBLl gene in cotton fiber development,we conducted phenotypic analysis on T1 generation of GhMYBL1 RNAi transgenic cotton materials.RT-PCR analysis showed that the expression of GhMYBL1 in transgenic cotton fiber decreased significantly.The mature fibers of different RNAi transgenic cotton strains were measured,and it was found that the fiber length and the length of short fleece did not change significantly.However,the secondary wall thickness of the fibrous cells decreased significantly.These results suggest that GhMYBL1 may play a positive regulatory role in secondary wall development of cotton fiber cells.2.GhMYBL1 can bind and activate the promoter of cellulase gene CesA 8-3-2To explore how GhMYBL1 regulates secondary wall development of fibers,we first conducted transcriptional activation experiments of GhMYBL1 and the promoter of cellulase gene.The results show that GhMYBL1 can bind to CesA8-3-2 promoter.Moreover,the prokaryotic expression and purification of GhMYBL1 protein were carried out,and the binding ability of GhMYBL1 to CesA8-3-2 promoter was verified in vitro through EMSA experiment.The above results indicate that GhMYBL1 transcription factor can activate the expression of the cellulase gene by binding to the CesA8-3-2 promoter,thus promoting the cellulose synthesis and deposition of secondary walls of cotton fiber cells.3.Screening and identification of GhARFs transcription factors that may regulate GhMYBLlIn order to explore the upstream gene of GhMYBL1 in the regulatory pathway,the promoter sequence of GhMYBL1 was analyzed,and it was found that there were multiple cis-acting sites of ARF transcription factors in the promoter sequence,and ARF is an important auxin signal response factor.Through evolutionary tree analysis and expression pattern analysis of GhARFs,we screened 14 GhARFs that may regulate GhMYBLl expression.There are 10 activated ARF transcription factors and 4 inhibitory ARF transcription factors.Then through the relevant experiments to verify.4.GhARFs transcription factor can activate the active expression of GhMYBLl promoterIn order to explore the transcriptional regulation of GhARFs on GhMYBLl gene,some GhARFs expression vectors were constructed and transcriptional activation experiments were conducted.The results showed that GhMYBL1 promoter activity was significantly enhanced by Gh_D07G0132 and Gh_D0160951 transcription factors.Furthermore,in vitro embryo experiments of cotton,it was found that secondary wall development of cotton fiber cells was significantly inhibited when IAA concentration decreased.The above experimental results indicate that some GhARFs may indeed be able to regulate GhMYBL1 gene expression and thus regulate secondary wall development of cotton fiber cells.