Ectopic expression of R3 MYB transcription factor gene OsTCL1 in Arabidopsis, but not rice, affects trichome and root hair formation.

Xutong Wang,Shucai Wang,Qingnan Hu,Li Yang,Bao Liu,Hainan Tian,Hongyan Guo,Kaijie Zheng,Ling Cai

doi:10.1038/srep19254

Abstract

In Arabidopsis, a MYB-bHLH-WD40 (MBW) transcriptional activator complex activates the homeodomain protein gene GLABRA2 (GL2), leading to the promotion of trichome formation and inhibition of root hair formation. The same MBW complex also activates single-repeat R3 MYB genes. R3 MYBs in turn, play a negative feedback role by competing with R2R3 MYB proteins for binding bHLH proteins, thus blocking the formation of the MBW complex. By BLASTing the rice (Oryza sativa) protein database using the entire amino acid sequence of Arabidopsis R3 MYB transcription factor TRICHOMELESS1 (TCL1), we found that there are two genes in rice genome encoding R3 MYB transcription factors, namely Oryza sativa TRICHOMELESS1 (OsTCL1) and OsTCL2. Expressing OsTCL1 in Arabidopsis inhibited trichome formation and promoted root hair formation, and OsTCL1 interacted with GL3 when tested in Arabidopsis protoplasts. Consistent with these observations, expression levels of GL2, R2R3 MYB transcription factor gene GLABRA1 (GL1) and several R3 MYB genes were greatly reduced, indicating that OsTCL1 is functional R3 MYB. However, trichome and root hair formation in transgenic rice plants overexpressing OsTCL1 remained largely unchanged, and elevated expression of OsGL2 was observed in the transgenic rice plants, indicating that rice may use different mechanisms to regulate trichome formation.

Highlights

GL1 or WER, GL3 or EGL3 and TTG1 form a MBW (MYB-bHLH-WD40) transcriptional activator complex to induce the expression of GL2, leading to the promotion of trichome formation and the inhibition of root hair formation[6,18,19]
We found that Oryza sativa TRICHOMELESS1 (OsTCL1) inhibited trichome formation and promoted root hair formation when expressed in Arabidopsis, trichome and root hair formation were largely unaffected in transgenic rice plant overexpressing OsTCL1, indicating that rice may use different mechanisms to regulate trichome and root hair formation
We found that expression of GFP-OsTCL1 in Arabidopsis inhibited trichome formation and promoted root hair formation (Fig. 2A,B), similar to that observed in the transgenic plants expressing OsTCL1(Fig. 2A,B), indicating that the GFP-OsTCL1 fusion protein is likely functional, the transgenic plant can be used to examine the subcellular localization of OsTCL1

Summary

Introduction

GL1 or WER, GL3 or EGL3 and TTG1 form a MBW (MYB-bHLH-WD40) transcriptional activator complex to induce the expression of GL2, leading to the promotion of trichome formation and the inhibition of root hair formation[6,18,19]. Some of the R3 MYBs including TCL1 and TCL2 can directly suppress the expression of GL17,8 These results suggest that R3 MYBs may use different mechanisms to regulate trichome and root hair formation in Arabidopsis. Single mutants of Arabidopsis R3 MYB genes have different phenotypes, over-expression of any of the R3 MYB genes from dicot plants inhibited trichome formation, and in some case, promoted root hair formation in Arabidopsis[7,10,11,21,34,35,36]. We found that OsTCL1 inhibited trichome formation and promoted root hair formation when expressed in Arabidopsis, trichome and root hair formation were largely unaffected in transgenic rice plant overexpressing OsTCL1, indicating that rice may use different mechanisms to regulate trichome and root hair formation

Methods

Results

Conclusion