Staffan Persson’s research while affiliated with IT University of Copenhagen and other places

Cell wall remodeling is important for plants to adapt to environmental stress. Under salt stress, cortical microtubules undergo a depolymerization-reassembly process to promote the biosynthesis of stress-adaptive cellulose, but the regulatory mechanisms underlying this process are still largely unknown. In this study, we reveal that FERONIA (FER), a potential cell wall sensor, interacts with COMPANION OF CELLULOSE SYNTHASE1 (CC1) and its closest homolog, CC2, two proteins that are required for cortical microtubule reassembly under salt stress. Biochemical data indicate that FER phosphorylates CC1 on multiple residues in its second and third hydrophobic microtubule-binding regions and that these phosphorylations modulate CC1 trafficking and affect the ability of CC1 to engage with microtubules. Furthermore, CC1 phosphorylation level is altered upon exposure to salt stress, which coincides with the changes of microtubule organization. Together, our study outlines an important intracellular mechanism that maintains microtubule arrays during salt exposure in plant cells.

Starch nanoparticles (sNPs) are considered ideal materials for applications in plant and agricultural sciences aiming at increasing crop yields, and improving resilience due to their non-toxicity, global availability, hydrophilicity, and...

Plant cells experience a variety of mechanical stresses from both internal and external sources, including turgor pressure, mechanical strains arising from heterogeneous growth between neighboring cells, and environmental factors like touch from soil, rain, or wind [1,2]. These stresses serve as signals at the cell-, tissue- and organismal level to coordinate plant growth during development and stress responses [3]. In plants, the physical cell wall-plasma membrane-microtubule continuum is proposed to be integral in transducing mechanical signals from the exterior to intracellular components [4–6]. Cortical microtubules (CMTs) rapidly reorient in response to mechanical stress to align with the maximal tensile stress direction [7,8]. Several studies proposed that CMTs themselves may act as stress sensors; the precise mechanisms involved in the regulation of CMTs and the modes of sensing, however, are still not clearly understood. Here, we show that IQD2 and KLCR1 are enriched at CMTs in proximity to the plasma membrane. IQD2, which is a bona fide microtubule-associated protein, promotes microtubule localization of KLCR1. By combining cross-linking mass spectrometry (XL-MS) and computational modeling with structure-function studies, we present first experimental insights into the composition and structure of IQD2-KLCR1 complexes. Further, we demonstrate that the IQD2-KLCR1 module is a positive regulator of microtubule mechano-responses in pavement cells. Collectively, our work identifies the IQD2-KLCR1 module as novel regulator of mechanostress-mediated CMT reorientation and provides a framework for future mechanistic studies aimed at a functional dissection of mechanotransduction at the plasma membrane-CMT interface during growth and plant morphogenesis. Highlights IQD2 and KLCR1 localize to the plasma membrane-microtubule nexus IQD2 is required for efficient microtubule targeting of KLCR1 in planta IQD2 physically interacts with KLCR1 and microtubules The IQD2-KLCR1 module promotes mechano-stress induced microtubule reorganization

Knowledge about how and where proteins interact provides a pillar for cell biology. Protein proximity-labelling has emerged as an important tool to detect protein interactions. Here, biotin-related proximity labelling approaches are by far the most commonly used, but may have labelling-related drawbacks. Here, we use pupylation-based proximity labelling (PUP-IT) as a tool for protein interaction detection in plants. We show that PUP-IT readily confirmed protein interactions for several known protein complexes across different types of plant hosts and that the approach increased detection of specific interactions as compared to biotin-based proximity labelling systems. To further demonstrate the power of PUP-IT, we used the system to identify protein interactions of the protein complex that underpin cellulose synthesis in plants. Apart from known complex components, we identified the ARF-GEF BEN1 (BFA-VISUALIZED ENDOCYTIC TRAFFICKING DEFECTIVE1). We show that BEN1 contributes to cellulose synthesis by regulating both clathrin-dependent and -independent endocytosis of the cellulose synthesis protein complex from the plasma membrane. Our results highlight PUP-IT as a powerful proximity labelling system to identify protein interactions in plant cells.

Helical growth of the root tip (circumnutation) that permits surface exploration facilitates root penetration into soil. Here, we reveal that rice actin-binding protein RMD aids in root circumnutation, manifested by wavy roots as well as compromised ability to efficiently explore and avoid obstacles in rmd mutants. We demonstrate that root circumnutation defects in rmd depend on brassinosteroid (BR) signaling, which is elevated in mutant roots. Suppressing BR signaling via pharmacological (BR inhibitor) or genetic (knockout of BR biosynthetic or signaling components) manipulation rescues root defects in rmd. We further reveal that mutations in MAPK6 suppress BR signaling and restore normal root circumnutation in rmd, which may be mediated by the interaction between MAPK6, MAPKK4 and BR signaling factor BIM2. Our study thus demonstrates that RMD and MAPK6 control root circumnutation by modulating BR signaling to facilitate early root growth.

Plant cell walls (PCWs) are intricate structures with complex polysaccharides delivered by distinct trafficking routes. Unravelling the intricate trafficking pathways of polysaccharides and proteins involved in PCW biosynthesis is a crucial first step towards understanding the complexities of plant growth and development. This study investigated the feasibility of employing a multi-modal approach that combines transmission electron microscopy (TEM) with molecular-genetic tagging and antibody labelling techniques to differentiate these pathways at the nanoscale. The genetically encoded electron microscopy (EM) tag APEX2 was fused to Arabidopsis thaliana cellulose synthase 6 (AtCESA6) and Nicotiana alata ARABINAN DEFICIENT LIKE 1 (NaARADL1), and these were transiently expressed in Nicotiana benthamiana leaves. APEX2 localization was then combined with immunolabeling using pectin-specific antibodies (JIM5 and JIM7). Our results demonstrate distinct trafficking patterns for AtCESA6 and NaARADL, with AtCESA6 localized primarily to the plasma membrane and vesicles, while NaARADL1 was found in the trans-Golgi network and cytoplasmic vesicles. Pectin epitopes were observed near the plasma membrane, in Golgi-associated vesicles, and in secretory vesicle clusters (SVCs) with both APEX2 constructs. Notably, JIM7 labelling was found in vesicles adjacent to APEX2-AtCESA6 vesicles, suggesting potential co-trafficking. This integrative approach offers a powerful tool for elucidating the dynamic interactions between PCW components at the nanoscale level. The methodology presented here facilitates the precise mapping of protein and polysaccharide trafficking pathways, advancing our understanding of PCW biosynthesis and providing avenues for future research aimed at engineering plant cell walls for various applications.

Isoxaben is a pre‐emergent herbicide used to control broadleaf weeds. While the phytotoxic mechanism is not completely understood, isoxaben interferes with cellulose synthesis. Certain mutations in cellulose synthase complex proteins can confer isoxaben tolerance; however, these mutations can cause compromised cellulose synthesis and perturbed plant growth, rendering them unsuitable as herbicide tolerance traits. We conducted a genetic screen to identify new genes associated with isoxaben tolerance by screening a selection of Arabidopsis thaliana T‐DNA mutants. We found that mutations in a FERREDOXIN‐NADP(+) OXIDOREDUCTASE‐LIKE (FNRL) gene enhanced tolerance to isoxaben, exhibited as a reduction in primary root stunting, reactive oxygen species accumulation and ectopic lignification. The fnrl mutant did not exhibit a reduction in cellulose levels following exposure to isoxaben, indicating that FNRL operates upstream of isoxaben‐induced cellulose inhibition. In line with these results, transcriptomic analysis revealed a highly reduced response to isoxaben treatment in fnrl mutant roots. The fnrl mutants displayed constitutively induced mitochondrial retrograde signalling, and the observed isoxaben tolerance is partially dependent on the transcription factor ANAC017, a key regulator of mitochondrial retrograde signalling. Moreover, FNRL is highly conserved across all plant lineages, implying conservation of its function. Notably, fnrl mutants did not show a growth penalty in shoots, making FNRL a promising target for biotechnological applications in breeding isoxaben tolerance in crops.

Adjacent plant cells are connected by specialized cell wall regions, called middle lamellae, which influence critical agricultural characteristics, including fruit ripening and organ abscission. Middle lamellae are enriched in pectin polysaccharides, specifically homogalacturonan (HG). Here, we identify a plant-specific Arabidopsis DUF1068 protein, called NKS1/ELMO4, that is required for middle lamellae integrity and cell adhesion. NKS1 localizes to the Golgi apparatus and loss of NKS1 results in changes to Golgi structure and function. The nks1 mutants also display HG deficient phenotypes, including reduced seedling growth, changes to cell wall composition, and tissue integrity defects. These phenotypes are comparable to qua1 and qua2 mutants, which are defective in HG biosynthesis. Notably, genetic interactions indicate that NKS1 and the QUAs work in a common pathway. Protein interaction analyses and modeling corroborate that they work together in a stable protein complex with other pectin-related proteins. We propose that NKS1 is an integral part of a large pectin synthesis protein complex and that proper function of this complex is important to support Golgi structure and function.

Precise regulation of cell proliferation and differentiation is vital for organ morphology. Rice palea, serving as sepal, comprises two distinct regions: the marginal region (MRP) and body of palea (BOP), housing heterogeneous cell populations, which makes it an ideal system for studying organ morphogenesis. We report that the transcription factor (TF) REP1 promotes epidermal cell proliferation and differentiation in the BOP, resulting in hard silicified protrusion cells, by regulating the cyclin-dependent kinase gene, OsCDKB1;1. Conversely, TFs OsMADS6 and OsMADS32 are expressed exclusively in the MRP, where they limit cell division rates by inhibiting OsCDKB2;1 expression and promote endoreduplication, yielding elongated epidermal cells. Furthermore, reciprocal inhibition between the OsMADS6-OsMADS32 complex and REP1 fine-tunes the balance between cell division and differentiation during palea morphogenesis. We further show the functional conservation of these organ identity genes in heterogeneous cell growth in Arabidopsis, emphasizing a critical framework for controlling cellular heterogeneity in organ morphogenesis.