Biology subjects

McFarlane, H. E.

Publications and source records attributed to McFarlane, H. E..

4 recordsLinked to original sources

bioRxiv2021

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

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.

plant biology↗

bioRxiv2020

A G protein-coupled receptor-like module regulates Cellulose Synthase secretion from the endomembrane system in Arabidopsis

Cellulose synthesis is essential for plant morphology, water transport and defense, and provides raw material for biomaterials and fuels. Cellulose is produced at the plasma membrane by Cellulose Synthase (CESA) protein complexes (CSCs). CSCs are assembled in the endomembrane system and then trafficked from the Golgi apparatus and trans-Golgi Network (TGN) to the plasma membrane. Since CESA enzymes are only active in the plasma membrane, control of CSC secretion is a critical step in the regulation of cellulose synthesis. However, the regulatory framework for CSC secretion is not clarified. In this study, we identify members of a family of seven transmembrane domain-containing proteins (7TMs) as important for cellulose production during cell wall integrity stress. 7TM proteins are often associated with guanine nucleotide-binding protein (G) protein signalling and mutants in several of the canonical G protein complex components phenocopied the 7tm mutant plants. Unexpectedly, the 7TM proteins localized to the Golgi apparatus/TGN where they interacted with the G protein complex. Here, the 7TMs and G proteins regulated CESA trafficking, but did not affect general protein secretion. Furthermore, during cell wall stress, 7TMs localization was biased towards small CESA-containing vesicles, specifically associated with CSC trafficking. Our results thus outline how a G protein-coupled module regulates CESA trafficking and reveal that defects in this process lead to exacerbated responses upon exposure to cell wall integrity stress.

plant biology↗

bioRxiv2020

Endomembrane Cation Chloride Cotransporters (CCC1s) modulate endo- and exocytosis

Plant cells maintain a low luminal pH in the Trans-Golgi-Network/Early Endosome (TGN/EE), the organelle in which the secretory and endocytic pathways intersect. Impaired TGN/EE pH regulation translates into severe plant growth defects. The identity of the proton pump and proton/ion antiporters that regulate TGN/EE pH have been determined, but an essential component required to complete the TGN/EE membrane transport circuit remains unidentified - a pathway for cation and anion efflux. Here, we have used complementation, genetically encoded fluorescent sensors, and pharmacological treatments to demonstrate that the TGN/EE localised Arabidopsis Cation Chloride Cotransporter (CCC1) is this missing component necessary for regulating TGN/EE pH and function. Loss of CCC1 function leads to alterations in TGN/EE-mediated processes including endo- and exocytosis, and trafficking to the vacuole, and response to abiotic stress, consistent with the multitude of phenotypes observed in ccc1 knockout plants. This discovery places CCC1 as a central component of plant cellular function.

plant biology↗

bioRxiv2018

A molecular mechanism for salt stress-induced microtubule array formation in Arabidopsis

Microtubules are filamentous structures necessary for cell division, motility and morphology, with dynamics critically regulated by microtubule-associated proteins (MAPs). We outline the molecular mechanism by which the MAP, COMPANION OF CELLULOSE SYNTHASE1 (CC1), controls microtubule bundling and dynamics to sustain plant growth under salt stress. CC1 contains an intrinsically disordered N-terminus that links microtubules at evenly distributed distances through four conserved hydrophobic regions. NMR analyses revealed that two neighboring residues in the first hydrophobic binding motif are crucial for the microtubule interaction, which we confirmed through live cell analyses. The microtubule-binding mechanism of CC1 is remarkably similar to that of the prominent neuropathology-related protein Tau, indicating evolutionary convergence of MAP functions across animal and plant cells.

cell biology↗