The transcription factor gamma MYB2 acts as a negative regulator of secondary cell wall thickening in anther and stem

Abstract

Secondary cell wall (SCW) thickening provides the mechanical force for anther dehiscence and plays an important role in the formation of xylem structure. We have previously reported that gamma MYB2, a MYB coiled-coil protein, directly binds to the P1BS cis-element of the PLA(2)-gamma promoter and acts as a co-activator of gamma MYB1 in controlling the expression of PLA(2)-gamma. In this study, we analyzed morphological phenotypes of the constitutive overexpression (gamma MYB2-OE) and knock-down (gamma MYB2-KD) lines of gamma MYB2. We found that gamma MYB2 over-expression caused the collapse of the endothecium layer, thereby suppressing anther dehiscence and forming short infertile siliques. The gamma MYB2-OE also showed less cellulose deposition in the xylem and had a longer primary stem than the wild-type, while gamma MYB2-KD had greater cellulose accumulation and a shorter primary stem than the wild-type. We demonstrated that the male sterility and the longer primary stem in gamma MYB2-OE were caused by reduced expression of SCW thickening-related genes. Our results suggest that gamma MYB2 acts as a negative regulator in controlling the SCW thickening in Arabidopsis.