Chitinase-like1/pom-pom1 and its homolog CTL2 are glucan-interacting proteins important for cellulose biosynthesis in Arabidopsis.
Plant cells are encased by a cellulose-containing wall that is essential for plant morphogenesis. Cellulose consists of β-1,4-linked glucan chains assembled into paracrystalline microfibrils that are synthesized by plasma membrane-located cellulose synthase (CESA) complexes. Associations with hemicelluloses are important for microfibril spacing and for maintaining cell wall tensile strength. Several components associated with cellulose synthesis have been identified; however, the biological functions for many of them remain elusive. We show that the chitinase-like (CTL) proteins, CTL1/POM1 and CTL2, are functionally equivalent, affect cellulose biosynthesis, and are likely to play a key role in establishing interactions between cellulose microfibrils and hemicelluloses. CTL1/POM1 coincided with CESAs in the endomembrane system and was secreted to the apoplast. The movement of CESAs was compromised in ctl1/pom1 mutant seedlings, and the cellulose content and xyloglucan structures were altered. X-ray analysis revealed reduced crystalline cellulose content in ctl1 ctl2 double mutants, suggesting that the CTLs cooperatively affect assembly of the glucan chains, which may affect interactions between hemicelluloses and cellulose. Consistent with this hypothesis, both CTLs bound glucan-based polymers in vitro. We propose that the apoplastic CTLs regulate cellulose assembly and interaction with hemicelluloses via binding to emerging cellulose microfibrils.
Max-Planck-Institut für Molekulare Pflanzenphysiologie, 14476 Potsdam-Golm, Germany.
Clara
C
Sánchez-Rodríguez
Stefan
S
Bauer
Kian
K
Hématy
Friederike
F
Saxe
Ana Belén
AB
Ibáñez
Vera
V
Vodermaier
Cornelia
C
Konlechner
Arun
A
Sampathkumar
Markus
M
Rüggeberg
Ernst
E
Aichinger
Lutz
L
Neumetzler
Ingo
I
Burgert
Chris
C
Somerville
Marie-Theres
MT
Hauser
Staffan
S
Persson
D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism; D002482:Cellulose / Q000096:biosynthesis*; D002688:Chitinases / Q000235:genetics / Q000378:metabolism*; D005936:Glucans / Q000378:metabolism*; D006026:Glycoside Hydrolases / Q000235:genetics / Q000378:metabolism*; D020894:Microfibrils / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics; D011134:Polysaccharides / Q000378:metabolism
D029681:Arabidopsis Proteins; D005936:Glucans; D011134:Polysaccharides; C007916:hemicellulose; D002482:Cellulose; C455513:CTL1 protein, Arabidopsis; D006026:Glycoside Hydrolases; D002688:Chitinases