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1. The Mode of Action of Endosidin20 Differs from That of Other Cellulose Biosynthesis Inhibitors

   https://doi.org/10.1093/pcp/pcaa136  

   Huang, Lei; Zhang, Chunhua (October 2020, Plant and Cell Physiology)

   null (Ed.)

   Abstract Endosidin20 (ES20) was recently identified as a cellulose biosynthesis inhibitor (CBI) that targets the catalytic domain of CELLULOSE SYNTHASE 6 (CESA6) and thus inhibits the growth of Arabidopsis thaliana. Here, we characterized the effects of ES20 on the growth of other plant species and found that ES20 is a broad-spectrum plant growth inhibitor. We tested the inhibitory effects of previously characterized CBIs (isoxaben, indaziflam and C17) on the growth of Arabidopsis cesa6 mutants that have reduced sensitivity to ES20. We found that most of these mutants are sensitive to isoxaben, indaziflam and C17, indicating that these tested CBIs have a different mode of action than ES20. ES20 also has a synergistic inhibitory effect on plant growth when jointly applied with other CBIs, further confirming that ES20 has a different mode of action than isoxaben, indaziflam and C17. We demonstrated that plants carrying two missense mutations conferring resistance to ES20 and isoxaben can tolerate the dual inhibitory effects of these CBIs when combined. ES20 inhibits Arabidopsis growth in growth medium and in soil following direct spraying. Therefore, our results pave the way for using ES20 as a broad-spectrum herbicide, and for the use of gene-editing technologies to produce ES20-resistant crop plants. 

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2. Point mutations in the catalytic domain disrupt cellulose synthase (CESA6) vesicle trafficking and protein dynamics

   https://doi.org/10.1093/plcell/koad110  

   Huang, Lei; Zhang, Weiwei; Li, Xiaohui; Staiger, Christopher J; Zhang, Chunhua (April 2023, The Plant Cell)

   Cellulose, the main component of the plant cell wall, is synthesized by the multimeric cellulose synthase (CESA) complex (CSC). In plant cells, CSCs are assembled in the endoplasmic reticulum or Golgi and transported through the endomembrane system to the plasma membrane (PM). However, how CESA catalytic activity or conserved motifs around the catalytic core influence vesicle trafficking or protein dynamics is not well understood. Here, we used yellow fluorescent protein (YFP)-tagged AtCESA6 and created 18 mutants in key motifs of the catalytic domain to analyze how they affected seedling growth, cellulose biosynthesis, complex formation, and CSC dynamics and trafficking in Arabidopsis thaliana. Seedling growth and cellulose content were reduced by nearly all mutations. Moreover, mutations in most conserved motifs slowed CSC movement in the PM as well as delivery of CSCs to the PM. Interestingly, mutations in the DDG and QXXRW motifs affected YFP-CESA6 abundance in the Golgi. These mutations also perturbed post-Golgi trafficking of CSCs. The 18 mutations were divided into 2 groups based on their phenotypes; we propose that Group I mutations cause CSC trafficking defects, whereas Group II mutations, especially in the QXXRW motif, affect protein folding and/or CSC rosette formation. Collectively, our results demonstrate that the CESA6 catalytic domain is essential for cellulose biosynthesis as well as CSC formation, protein folding and dynamics, and vesicle trafficking. 

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3. A fungal natural product that inhibits plant cellulose biosynthesis by disrupting cellulose synthase complexes

   https://doi.org/10.1073/pnas.2602575123  

   Wu, Zhongshou; Liu, Lu; Han, Wenyu; Cai, Xingbo; Xiao, Pixian; Sun, Zuodong; Yan, Chunsheng; Reid, Silvana; Chen, Yun; Ma, Zhonghua; et al (June 2026, Proceedings of the National Academy of Sciences)

   Cellulose, a primary component of plant cell walls, is synthesized by cellulose synthase complexes (CSCs) at the plasma membrane. Targeting this process with cellulose biosynthesis inhibitors (CBIs) has significantly advanced our understanding of plant cell wall formation and provided valuable compounds for herbicide development. Here, we identified a fungal natural product, 8-methyldichlorodiaporthin (MDD), as a broad-spectrum plant CBI. Structure–activity relationship analyses demonstrate that methylation modifications on the isocoumarin ring and chlorination of the side chain are crucial for MDD-induced growth inhibition. A chemical forward genetic screen inArabidopsis thalianarevealed two semidominant CESA1 mutations, causing A903T and H1024Y substitutions, that confer insensitivity to MDD. Both mutations locate to transmembrane domains of CESA1, and we show that MDD depletes CSCs from the plasma membrane and reduces cellulose content. Further genetic analyses indicate that thecesa1^mddi1-1A903Tmutant also confers resistance to CBIs quinoxyphen and C17, but not to CBIs isoxaben, indaziflam, or ES20. Stacking additional point mutations conferring resistance to other CBIs,cesa3^ixr1-1G998D, andcesa6^es20-r3G935Einto thecesa1^mddi1-1A903Tbackground yields multiple-drug-resistant lines that maintain normal growth. These findings establish MDD, as a natural CBI that likely targets CESA1, thereby extending our understanding of CSC regulation and abilities to develop multidrug-resistant crop varieties. These findings offer unique perspectives for weed management and plant biotechnology. 

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4. An alternate route for cellulose microfibril biosynthesis in plants

   https://doi.org/10.1126/sciadv.adr5188  

   Roberts, Eric M; Yuan, Kai; Chaves, Arielle M; Pierce, Ethan T; Cresswell, Rosalie; Dupree, Ray; Yu, Xiaolan; Blanton, Richard L; Wu, Shu-Zon; Bezanilla, Magdalena; et al (December 2024, Science Advances)

   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 mossPhyscomitrium patensto 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 inP. patensprotonemal 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 Ca²⁺, rather than structural differences in the microfibrils they produce. 

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5. Biochemical and Genetic Analysis Identify CSLD3 as a beta-1,4-glucan Synthase that Functions during Plant Cell Wall Synthesis.

   https://doi.org/doi: 10.1105/tpc.19.00637  

   *Yang J., *Bak G. (May 2020, The plant cell)

   In plants, changes in cell size and shape during development fundamentally depend on the ability to synthesize and modify cell wall polysaccharides. The main classes of cell wall polysaccharides produced by terrestrial plants are cellulose, hemicelluloses, and pectins. Members of the cellulose synthase (CESA) and cellulose synthase-like (CSL) families encode glycosyltransferases that synthesize the β-1,4-linked glycan backbones of cellulose and most hemicellulosic polysaccharides that comprise plant cell walls. Cellulose microfibrils are the major load-bearing component in plant cell walls and are assembled from individual β-1,4-glucan polymers synthesized by CESA proteins that are organized into multimeric complexes called CESA complexes, in the plant plasma membrane. During distinct modes of polarized cell wall deposition, such as in the tip growth that occurs during the formation of root hairs and pollen tubes or de novo formation of cell plates during plant cytokinesis, newly synthesized cell wall polysaccharides are deposited in a restricted region of the cell. These processes require the activity of members of the CESA-like D subfamily. However, while these CSLD polysaccharide synthases are essential, the nature of the polysaccharides they synthesize has remained elusive. Here, we use a combination of genetic rescue experiments with CSLD-CESA chimeric proteins, in vitro biochemical reconstitution, and supporting computational modeling and simulation, to demonstrate that Arabidopsis (Arabidopsis thaliana) CSLD3 is a UDP-glucose-dependent β-1,4-glucan synthase that forms protein complexes displaying similar ultrastructural features to those formed by CESA6. 

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