A DUF1068 protein acts as a pectin biosynthesis scaffold and maintains Golgi morphology and cell adhesion in Arabidopsis

Abstract

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, that is required for middle lamellae integrity and cell adhesion. NKS1 localises to the Golgi apparatus and loss of the protein 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 identical to those of the HG deficient mutants qua1 and qua2. Notably, NKS1 physically interacts with both QUA1 and QUA2, and genetic interaction analyses reveal that they work in the same pathway. Based on these results we propose that NKS1 works as a scaffold for HG synthesis and that such scaffolding is important to support Golgi function and the organization of the pectin synthesis machinery.

Cell adhesion maintenance and controlled separation in plants

“…In addition to QUA1, QUA2, ESMD1, and FRB1, two new gene families have recently been identified to act in the same pathway. Mutation in the genes coding for Golgi membrane localized protein ELMO1, ELMO2 and ELMO4/NKS1 (Kohorn et al, 2021;Lathe et al, 2021) as well as Golgi-localized putative S-adenosyl methionine transporters (GoSAMT1 and GoSAMT2) (Temple et al, 2022) also lead to a strong defect in cell-cell adhesion which can be rescued by esmd1. ELMO family proteins are suspected to act as scaffold for QUA1 and QUA2 in the Golgi (Lathe et al, 2021;Kohorn et al, 2023) and GoSAMT transporter should be necessary to provide the S-adenosyl methionine for HG methyl esterification by QUA2 in the Golgi.…”

Characterising the mechanics of cell–cell adhesion in plants

“…The importance of these types of cross-linking for cell adhesion has been supported by the characterisation of celladhesion defective mutants. For instance, in Arabidopsis, several mutations in genes involved in HG synthesis (Bouton et al, 2002;Du et al, 2020;Lathe et al, 2021;Mouille et al, 2007;Temple et al, 2021), remodelling (Francis et al, 2006;Lionetti et al, 2015) or degradation (Ogawa et al, 2009;Rhee et al, 2003;Rui et al, 2019) harbour cell-adhesion phenotypes (loss of cell adhesion or incapacity of cell separation). Furthermore, selectively digesting the cell wall with pectin degrading enzymes, such as polygalacturonases, and even chelating the cell wall calcium with chelators, such as EDTA, can also lead to cell separation (Letham, 1960;McCartney & Knox, 2002;Ng et al, 2000;Zhang et al, 2000).…”

Review: Characterising the mechanics of cell–cell adhesion in plants — R0/PR2

“…The importance of these types of cross-linking for cell adhesion has been supported by the characterisation of celladhesion defective mutants. For instance, in Arabidopsis, several mutations in genes involved in HG synthesis (Bouton et al, 2002;Du et al, 2020;Lathe et al, 2021;Mouille et al, 2007;Temple et al, 2021), remodelling (Francis et al, 2006;Lionetti et al, 2015) or degradation (Ogawa et al, 2009;Rhee et al, 2003;Rui et al, 2019) harbour cell-adhesion phenotypes (loss of cell adhesion or incapacity of cell separation). Furthermore, selectively digesting the cell wall with pectin degrading enzymes, such as polygalacturonases, and even chelating the cell wall calcium with chelators, such as EDTA, can also lead to cell separation (Letham, 1960;McCartney & Knox, 2002;Ng et al, 2000;Zhang et al, 2000).…”