Takahashi J, Rudsander UJ, Hedenström M, Banasiak A, Harholt J, Amelot N, Immerzeel P, Ryden P, Endo S, Ibatullin FM, Brumer H, del Campillo E, Master ER, Vibe Scheller H, Sundberg B, Teeri TT, Mellerowicz EJ
KORRIGAN1 and its aspen homologue PttCel9A1 decrease cellulose crystallinity in Arabidopsis stems
Plant and Cell Physiology: 2009 50:1099-1115

Abstract
KORRIGAN1 (KOR1) is a membrane-bound cellulase implicated incellulose biosynthesis. PttCel9A1 from hybrid aspen (Populustremula L. x tremuloides Michx.) has high sequence similarityto KOR1 and we demonstrate here that it complements kor1-1 mutants,indicating that it is a KOR1 ortholog. We investigated thefunction of PttCel9A1/KOR1 in Arabidopsis secondary growth usingtransgenic lines expressing 35S::PttCel9A1 and the KOR1 mutantline irx2-2. The presence of elevated levels of PttCel9A1/KOR1in secondary walls of 35S::PttCel9A1 lines was confirmed byin muro visualization of cellulase activity. Compared to WT,35S::PttCel9A1 lines had higher trifluoroacetic acid (TFA)-hydrolyzableglucan contents, similar Updegraff cellulose contents and lowercellulose crystallinity indices, as determined by 13C solidstate NMR spectroscopy. Irx2-2 mutants had wild type TFA-hydrolyzableglucan contents, but reduced Updegraff cellulose contents andhigher than wild type cellulose crystallinity indices. Thedata support the hypothesis that PttCel9A1/KOR1 activity ispresent in cell walls, where it facilitates cellulose biosynthesisin a way that increases the amount of non-crystalline cellulose.

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