Functional Characterization Of R3 MYB Transcription Factor In Soybean

Trichome is a kind of structure belongs to the land plants.It can reduce the disoperation from stinging insects and other insect pests.In addition,trichome can also reduce the water loss and provide UV protection for plants.Therefore,it is necessary for researchers to do some research related to the trichome.The R3 MYB transcription factors in Arabidopsis are negative regulators of trichome formation.R3 MYB proteins inhibit trichome formation in Arabidopsis by competing with the R2R3 MYB transcription factor GLABRA1(GL1)for binding the bHLH transcription factor GLABRA3(GL3)or ENHANCER OF GL3(EGL3),thus blocking the formation of the MYB-bHLH-WD40(MBW)transcriptional activator complex formed by GL1,GL3/EGL3 and the WD40-repeat transcription factor TRANSPARENT TESTA GLABRA1(TTG1).The MBW complex can activate the expression of the homedomain transcription factor gene GLABRA2(GL2),whereas GL2 is required for trichome formation.However,it remains unclear where R3 MYB transcription factors in soybean may involve in the regulation of trichome formation.At first,we found the amino acid sequence of the Arabidopsis R3 MYB transcription factor TRICHOMELESS1(TCL1).Then,in the soybean(Glycine max)protein database,we used the technique of BLAST to search for R3 MYB transcription factors belong to soybean.we found that there are six R3 MYBs in soybean.We call them GmTCL1 to GmTCL6.Sequence alignment analysis indicates that GmTCLs are typical R3 MYB transcription factors.By generating transgenic plants,we found that trichome formation in soybean plants overexpressing each of the GmTCLs remained largely unchanged,and the expression of putative GL1 and GL2 genes in the transgenic soybean plants was unaffected.On the other hand,expressing each of the GmTCLs under the control of the 35 S promoter in Arabidopsis inhibited trichome formation,and the expression levels of GL1 and GL2 were greatly reduced in the Arabidopsis transgenic plants.In addition,all the GmTCLs interacted with GLABRA3(GL3)in transfected Arabidopsis protoplasts.Moreover,expressing GmTCL1 under the control of the Arabidopsis TCL1 promoter completely restored the tcl1 mutant phenotypes,indicating that GmTCL1 is functionally equivalent to TCL1.Taken together,these results suggest that GmTCLs are able to regulate trichome formation in arabidopsis,however,they may not play a role in regulating trichome formation in soybean.