Leucine-Rich Repeat Extensin Proteins and Their Role in Cell Wall Sensing

Abstract

Plant cells are surrounded by a cell wall that provides shape and physically limits cell expansion. To sense the environment and status of cell wall structures, plants have evolved cell wall integrity-sensing mechanisms that involve a number of receptors at the plasma membrane. These receptors can bind cell wall components and/or hormones to coordinate processes in the cell wall and the cytoplasm. This review focuses on the role of leucine-rich repeat extensins (LRXs) during cell wall development. LRXs are chimeric proteins that insolubilize in the cell wall and form protein-protein interaction platforms. LRXs bind RALF peptide hormones that modify cell wall expansion and also directly interact with the transmembrane receptor FERONIA, which is involved in cell growth regulation. LRX proteins, therefore, also represent a link between the cell wall and plasma membrane, perceiving extracellular signals and indirectly relaying this information to the cytoplasm.

The Genome-Wide Analysis of RALF-Like Genes in Strawberry (Wild and Cultivated) and Five Other Plant Species (Rosaceae)

“…The GO terms give a clear function cluster of RALF-like genes, which involved in the pollen tube development, root development, negative regulation of growth, cell wall growth, hormone activaty, brassinosteroid-mediated signaling pathway, and so on. According to the classification, we found they are very consistent with previous researches about the functions of RALF genes [1,[14][15][16][17][18]64]. Fungal infection response and pollen tube development are important for Rosaceae species, and the RALF-like gene expression in seed and fruit among Rosaceae species specially.…”

“…As reported, RALF genes are not only involved in several biotic and abiotic stresses but also influence the growth and development of plants. Here, we found that the expression profiles are mostly similar with the researchers reported, such as the drought response [13], root growth [64], hormone response [18], fungi response [18][19][20], cell wall development [15,17], and the flower development (especially the development of pollen tube) [14,16]. In the present study, we combined the results of RNA-seq, EST data, cis-regulatory elements analysis, and RT-qPCR to identify several genes which have identical expression profiles in two or more analyses, which may give some instructions of the research of RALF-like genes among Rosaceae species.…”

“…ScRALF23 was reported as able to affect the pollen mitosis by functioning among the process from sporophyte to gametophyte signaling [16]. Leucine-rich repeat extension proteins can combine with RALF to modify cell wall expansion and bind to the transmembrane receptor FERONIA and regulate the cell growth [17]. Haruta et al [18] reported that PtdRALF1 and PtdRALF2 were continuously and stably expressed in several organs, whereas PtdRALF2 showed low expression in the leaves of mature poplar trees, and PtdRALF1 was hardly affected by phytohormones, nutrient concentration pathogen elicitors, and decreasing pH caused by HCl, but the expression of PtdRALF2 could be inhibited strongly by MeJA after 5 h. Gupta et al [19] reported that the expression of RALF in resistant chickpeas was induced by Fusarium oxysporum f. sp.…”

“…RALF23 can induce the FER to stabilize MYC2 and promote the JA-dependent response [21]. LRX1, the main LRX protein of root hairs, can interact with FER and RALF1 to coordinate growth processes [17]. RALF genes function extensively, but the researches in Rosaceae species are little, some evidences have been provided that RALF will influence the development of pollen tube and can respond to the fungal infection.…”

Pattern recognition receptors confer plant salt tolerance via WRKY18/WRKY40 transcription factors

“…DAMPs represent a common signature of biotic and abiotic stress conditions in animals and plants (Gust et al, 2017;De Lorenzo et al, 2018). In plants, abiotic modulation of cell walls and phospholipid membranes generates a battery of DAMPs (Chen et al, 2020;Rui & Dinneny, 2020;Herger et al, 2019;Jiang et al, 2019).…”