AUTHOR=Li Chaofeng , Ma Xiaodong , Yu Hong , Fu Yongyao , Luo Keming 

TITLE=Ectopic Expression of PtoMYB74 in Poplar and Arabidopsis Promotes Secondary Cell Wall Formation

JOURNAL=Frontiers in Plant Science

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2018.01262

DOI=10.3389/fpls.2018.01262

ISSN=1664-462X

ABSTRACT=<p>In vascular plants, R2R3-MYB transcription factors are important regulators of secondary cell wall formation. Although 192 annotated R2R3 MYB genes were identified in the poplar genome, only a few members were characterized to participate in the regulation of the secondary cell wall biosynthesis. In this paper, we identify an R2R3-MYB transcription factor, <italic>PtoMYB74</italic>, which is predicted to be an ortholog of <italic>Arabidopsis AtMYB61</italic>, a transcription activator that regulates the secondary cell wall formation, lignin biosynthesis, stomatal aperture, and the mucilage of seed coat. <italic>PtoMYB74</italic> is mainly expressed in the stems, especially in the xylem tissues and organs. <italic>PtoMYB74</italic> as a transcriptional activator is localized to the nucleus. The overexpression of <italic>PtoMYB74</italic> increased the secondary cell wall thickness of vessels in transgenic poplar and changed the secondary cell wall compositions. The expression levels of lignin and cellulose biosynthetic genes were elevated in the transgenic poplar overexpressing <italic>PtoMYB74</italic> compared to the wild type, while there was no change in the xylan biosynthetic genes. Transcriptional activation assays demonstrated that <italic>PtoMYB74</italic> could activate the promoters of structural genes in the lignin and cellulose biosynthetic pathways. Taken together, our data show that <italic>PtoMYB74</italic> positively regulates the secondary cell wall biosynthesis in poplar.</p>