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SECONDARY WALL ASSOCIATED MYB 1 is a positive regulator of secondary cell wall thickening in Brachypodium distachyon and is not found in the Brassicaceae
Author(s) -
Handakumbura Pubudu P.,
Brow Kathryn,
Whitney Ian P.,
Zhao Kangmei,
Sanguinet Karen A.,
Lee Scott J.,
Olins Jennifer,
RomeroGamboa Sandra P.,
Harrington Michael J.,
Bascom Carlisle J.,
MacKin Kirk JM.,
Veling Michael T.,
Liu Lifeng,
Lee Ji E.,
Vogel John P.,
O'Malley Ronan C.,
Bezanilla Magdalena,
Bartley Laura E.,
Hazen Samuel P.
Publication year - 2018
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.14047
Subject(s) - brachypodium distachyon , secondary cell wall , brachypodium , cell wall , lignin , biology , xylem , myb , botany , promoter , gene , brassicaceae , microbiology and biotechnology , transcription factor , gene expression , genetics , genome
Summary Grass biomass is comprised chiefly of secondary walls that surround fiber and xylem cells. A regulatory network of interacting transcription factors in part regulates cell wall thickening. We identified Brachypodium distachyon SECONDARY WALL ASSOCIATED MYB 1 ( SWAM 1 ) as a potential regulator of secondary cell wall biosynthesis based on gene expression, phylogeny, and transgenic plant phenotypes. SWAM 1 interacts with cellulose and lignin gene promoters with preferential binding to AC ‐rich sequence motifs commonly found in the promoters of cell wall‐related genes. SWAM 1 overexpression ( SWAM ‐ OE ) lines had greater above‐ground biomass with only a slight change in flowering time while SWAM 1 dominant repressor ( SWAM 1‐ DR ) plants were severely dwarfed with a striking reduction in lignin of sclerenchyma fibers and stem epidermal cell length. Cellulose, hemicellulose, and lignin genes were significantly down‐regulated in SWAM 1‐ DR plants and up‐regulated in SWAM 1‐ OE plants. There was no reduction in bioconversion yield in SWAM 1‐ OE lines; however, it was significantly increased for SWAM 1‐ DR samples. Phylogenetic and syntenic analyses strongly suggest that the SWAM 1 clade was present in the last common ancestor between eudicots and grasses, but is not in the Brassicaceae. Collectively, these data suggest that SWAM 1 is a transcriptional activator of secondary cell wall thickening and biomass accumulation in B. distachyon .