An alternate route for cellulose microfibril biosynthesis in plants.

Roberts, Eric M; Yuan, Kai; Chaves, Arielle M; Pierce, Ethan T; Cresswell, Rosalie; Dupree, Ray; Yu, Xiaolan; Blanton, Richard L et al. · Sci Adv · 2024

basic_science · Level V

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Abstract

Similar to cellulose synthases (CESAs), cellulose synthase-like D (CSLD) proteins synthesize β-1,4-glucan in plants. CSLDs are important for tip growth and cytokinesis, but it was unknown whether they form membrane complexes in vivo or produce microfibrillar cellulose. We produced viable CESA-deficient mutants of the moss <i>Physcomitrium patens</i> to investigate CSLD function without interfering CESA activity. Microscopy and spectroscopy showed that CESA-deficient mutants synthesize cellulose microfibrils that are indistinguishable from those in vascular plants. Correspondingly, freeze-fracture electron microscopy revealed rosette-shaped particle assemblies in the plasma membrane that are indistinguishable from CESA-containing rosette cellulose synthesis complexes (CSCs). Our data show that proteins other than CESAs, most likely CSLDs, produce cellulose microfibrils in <i>P. patens</i> protonemal filaments. The data suggest that the specialized roles of CSLDs in cytokinesis and tip growth are based on differential expression and different interactions with microtubules and possibly Ca<sup>2+</sup>, rather than structural differences in the microfibrils they produce.

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