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1. 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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2. The TRAPPIII subunit, Trs85, has a dual role in the trafficking of cellulose synthase complexes in Arabidopsis

   https://doi.org/10.1111/tpj.16688  

   Allen, Holly; Zhu, Xiaoyu; Li, Shundai; Gu, Ying (June 2024, The Plant Journal)

   SUMMARY Plant cell walls are essential for defining plant growth and development, providing structural support to the main body and responding to abiotic and biotic cues. Cellulose, the main structural polymer of plant cell walls, is synthesized at the plasma membrane by cellulose synthase complexes (CSCs). The construction and transport of CSCs to and from the plasma membrane is poorly understood but is known to rely on the coordinated activity of cellulose synthase‐interactive protein 1 (CSI1), a key regulator of CSC trafficking. In this study, we found that Trs85, a TRAPPIII complex subunit, interacted with CSI1in vitro. Using functional genetics and live‐cell imaging, we have shown thattrs85‐1mutants have reduced cellulose content, stimulated CSC delivery, an increased population of static CSCs and deficient clathrin‐mediated endocytosis in the primary cell wall. Overall, our findings suggest that Trs85 has a dual role in the trafficking of CSCs, by negatively regulating the exocytosis and clathrin‐mediated endocytosis of CSCs. 

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3. B4 Raf‐like MAPKKK RAF24 regulates Arabidopsis thaliana flowering time through HISTONE MONO ‐ UBIQUITINATION 2

   https://doi.org/10.1111/nph.70192  

   Li, Qiaomu; Wang, Le; Grubb, Lauren E; Talasila, Mohana; Rodriguez_Gallo, Maria Camila; Mehta, Devang; Scandola, Sabine; Uhrig, Richard Glen (July 2025, New Phytologist)

   Summary The timing of flowering is a critical agronomic trait governed by an extensive and sophisticated regulatory network. To date, limited understanding of how posttranslational modifications regulate flowering time exists. Here, using Arabidopsis, we resolve a role for the B4 Raf‐like MAPKKK protein kinase RAF24 in regulating flowering time.Loss of RAPIDLY ACCELERATED FIBROSARCOMA24 (RAF24) led to premature flowering time through altered expression ofFLCandFT. Comparative phosphoproteomic analysis ofraf24and wild‐type plants revealed a list of known flowering‐related phosphoproteins from distinct flowering pathways displaying downregulated phosphorylation. Of these, the RING‐type ubiquitin ligase HISTONE MONO‐UBIQUITINATION 2 (HUB2) lacked phosphorylation in the absence of RAF24.Absence of RAF24 induced H2Bub1 overaccumulation, with protein–protein interactome analysis of HUB2 in the presence and absence of RAF24 influencing HUB2 protein interaction partners, such as H2B. HUB2 was also found to physically interact with SUCROSE NONFERMENTING KINASE 2.4 (SnRK2.4) and SnRK2.6, known substrates of RAF24. Using phospho‐mimetic and phospho‐ablative plant lines, we then validated the importance of HUB2 phosphorylation at serine 314 (S314) in maintaining appropriate flowering time.Our findings uncovered a novel biological role of RAF24, as a higher‐order flowering regulator, while further implicating HUB2 as a centerpiece of flowering time regulation. 

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4. 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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5. mRNA ADENOSINE METHYLASE promotes drought tolerance through N⁶ ‐methyladenosine‐dependent and independent impacts on mRNA regulation in Arabidopsis

   https://doi.org/10.1111/nph.20227  

   Ganguly, Diep R; Li, Yongfang; Bhat, Susheel Sagar; Tiwari, Shalini; Ng, Pei Jia; Gregory, Brian D; Sunkar, Ramanjulu (October 2024, New Phytologist)

   Summary Among many mRNA modifications, adenine methylation at the N⁶position (N⁶‐methyladenosine, m⁶A) is known to affect mRNA biology extensively. The influence of m⁶A has yet to be assessed under drought, one of the most impactful abiotic stresses.We show thatArabidopsis thaliana(L.) Heynh. (Arabidopsis) plants lacking mRNA ADENOSINE METHYLASE (MTA) are drought‐sensitive. Subsequently, we comprehensively assess the impacts of MTA‐dependent m⁶A changes during drought on mRNA abundance, stability, and translation in Arabidopsis.During drought, there is a global trend toward hypermethylation of many protein‐coding transcripts that does not occur inmta. We also observe complex regulation of m⁶A at a transcript‐specific level, possibly reflecting compensation by other m⁶A components. Importantly, a subset of transcripts that are hypermethylated in an MTA‐dependent manner exhibited reduced turnover and translation inmta, compared with wild‐type (WT) plants, during drought. Additionally, MTA impacts transcript stability and translation independently of m⁶A. We also correlate drought‐associated deposition of m⁶A with increased translation of modulators of drought response, such asRD29A,COR47,COR413,ALDH2B,ERD7, andABF4in WT, which is impaired inmta.m⁶A is dynamic during drought and, alongside MTA, promotes tolerance by regulating drought‐responsive changes in transcript turnover and translation. 

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