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

Abstract

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) 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 (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, 7TM 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.

The α subunit of the heterotrimeric G protein regulates mesophyll CO2 conductance and drought tolerance in rice

“…Reduced cell wall thickness in the d1 mutant is supported by the latest finding that RGA1 modulates genes involved in cell wall composition in rice (Pathak et al ., 2021). Moreover, in Arabidopsis, G proteins have been shown to interact with proteins involved in cell wall modification (Klopffleisch et al ., 2011) and to regulate trafficking of cellulose synthase to the plasma membrane (McFarlane et al ., 2021). Indeed, differences in cell wall composition of G protein mutants have been identified by Fourier transform infrared spectroscopy (Delgado‐Cerezo et al ., 2012).…”

Plant endosomes as protein sorting hubs

“…There is robust evidence supporting multiple exocytic pathways operating at the plant TGN. For example, 7TM (seven transmembrane domain-containing) proteins act at the Golgi and TGN to regulate exocytosis of cellulose synthases but do not control general exocytosis of both soluble and plasma membrane proteins [70]. In addition, the TGN-localized protein ECHIDNA mediates the secretion of cell wall matrix polysaccharides (e.g., pectins, xyloglucans) [66,71,72] and the plasma membrane localization of the auxin influx carrier AUX1 [73].…”

Global Disease Burden of Respiratory Syncytial Virus in Preterm Children in 2019: A Systematic Review and Individual Participant Data Meta-Analysis Protocol

“…By contrast, a module formed by seven transmembrane domain-containing proteins (7TM) and components of guanine nucleotide-binding (G) protein signaling function together at the Golgi and TGN to regulate the exocytosis of cellulose synthases, but not the endocytosis or general exocytosis of soluble or PM cargoes (McFarlane et al, 2021).…”