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p ‐Coumaroyl‐ C o A :monolignol transferase ( PMT ) acts specifically in the lignin biosynthetic pathway in B rachypodium distachyon
Author(s) -
Petrik Deborah L.,
Karlen Steven D.,
Cass Cynthia L.,
Padmakshan Dharshana,
Lu Fachuang,
Liu Sarah,
Bris Philippe,
Antelme Sébastien,
Santoro Nicholas,
Wilkerson Curtis G.,
Sibout Richard,
Lapierre Catherine,
Ralph John,
Sedbrook John C.
Publication year - 2014
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.12420
Subject(s) - monolignol , brachypodium distachyon , lignin , chemistry , biochemistry , phenylpropanoid , mutant , cell wall , acyltransferases , enzyme , biosynthesis , gene , organic chemistry , genome
Summary Grass lignins contain substantial amounts of p ‐coumarate ( p CA ) that acylate the side‐chains of the phenylpropanoid polymer backbone. An acyltransferase, named p ‐coumaroyl‐CoA:monolignol transferase ( O s PMT ), that could acylate monolignols with p CA in vitro was recently identified from rice. In planta , such monolignol‐ p CA conjugates become incorporated into lignin via oxidative radical coupling, thereby generating the observed p CA appendages; however p ‐coumarates also acylate arabinoxylans in grasses. To test the authenticity of PMT as a lignin biosynthetic pathway enzyme, we examined B rachypodium distachyon plants with altered BdPMT gene function. Using newly developed cell wall analytical methods, we determined that the transferase was involved specifically in monolignol acylation. A sodium azide‐generated Bdpmt‐1 missense mutant had no (<0.5%) residual p CA on lignin, and BdPMT RNA i plants had levels as low as 10% of wild‐type, whereas the amounts of p CA acylating arabinosyl units on arabinoxylans in these PMT mutant plants remained unchanged. p CA acylation of lignin from BdPMT ‐overexpressing plants was found to be more than three‐fold higher than that of wild‐type, but again the level on arabinosyl units remained unchanged. Taken together, these data are consistent with a defined role for grass PMT genes in encoding BAHD (BEAT, AHCT, HCBT, and DAT) acyltransferases that specifically acylate monolignols with p CA and produce monolignol p ‐coumarate conjugates that are used for lignification in planta .