Abstract
Multiple cellulose synthase (CesA) subunits assemble into plasma membrane complexes responsible for cellulose production. In the Arabidopsis (Arabidopsis thaliana) model system, we identified a novel D604N missense mutation, designated anisotropy1 (any1), in the essential primary cell wall CesA1. Most previously identified CesA1 mutants show severe constitutive or conditional phenotypes such as embryo lethality or arrest of cellulose production but any1 plants are viable and produce seeds, thus permitting the study of CesA1 function. The dwarf mutants have reduced anisotropic growth of roots, aerial organs, and trichomes. Interestingly, cellulose microfibrils were disordered only in the epidermal cells of the any1 inflorescence stem, whereas they were transverse to the growth axis in other tissues of the stem and in all elongated cell types of roots and dark-grown hypocotyls. Overall cellulose content was not altered but both cell wall crystallinity and the velocity of cellulose synthase complexes were reduced in any1. We crossed any1 with the temperature-sensitive radial swelling1-1 (rsw1-1) CesA1 mutant and observed partial complementation of the any1 phenotype in the transheterozygotes at rsw1-1's permissive temperature (21°C) and full complementation by any1 of the conditional rsw1-1 root swelling phenotype at the restrictive temperature (29°C). In rsw1-1 homozygotes at restrictive temperature, a striking dissociation of cellulose synthase complexes from the plasma membrane was accompanied by greatly diminished motility of intracellular cellulose synthase-containing compartments. Neither phenomenon was observed in the any1 rsw1-1 transheterozygotes, suggesting that the proteins encoded by the any1 allele replace those encoded by rsw1-1 at restrictive temperature.
Highlights
Multiple cellulose synthase (CesA) subunits assemble into plasma membrane complexes responsible for cellulose production
Cellulose microfibrils are major tension-bearing components of the cell walls of vascular plants. They consist of multiple b-1,4-linked glucan chains, which are synthesized at the plasma membrane from multiCesA enzyme complexes, known as cellulose synthase complexes (CSCs) or rosettes (Brown et al, 1996; Kimura et al, 1999)
In this study we have shown that the impaired growth anisotropy in the any1 mutant is severe in epidermal cells
Summary
The any mutant was isolated from M2 lines of an ethyl methanesulfonate-treated population. FESEM analyses on the any root and dark-grown hypocotyl epidermal cells demonstrated that any cellulose microfibrils aligned transversely to the cell growth axis as in wild-type plants (Supplemental Fig. S2). We measured the CSC velocities either in seedlings grown at 21°C for 3 d, or at 21°C for 2 d and 29°C for 1 d At both temperatures, we noted that 3-dold dark-grown seedlings expressing YFP-CesA6 in any had shorter hypocotyls compared with the wild type (Supplemental Fig. S3), indicating that mutant dwarf phenotypes are consistent in the hypocotyls at both temperatures. Analysis of hypocotyl length and diameter in dark-grown wild-type, any, rsw, and any1/rsw transheterozygotes expressing YFP-CesA6 confirmed that there is partial allelic complementation in the any rsw transheterozygote similar to that observed in the roots (Supplemental Fig. S3). The CSC catalytic velocity at the plasma membrane in transheterozygotes was 227 6 102 nm min–1 (Fig. 7B), similar to that of any at 29°C
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
