A comparative analysis of Receptor Like Kinases in Chlorophyta reveals the presence of putative Cell Wall Integrity sensors.

Description

Abstract

Receptor-like kinases (RLKs) perceive extracellular signals from other organisms as well as from the individuum itself, triggering responses essential for growth and adaptation. Among these self-derived signals, a relevant role is sensing cell wall integrity (CWI), whereby changes in cell wall structure or composition activate cellular responses critical for development and defense. While RLKs are well characterized in vascular plants, their diversity and function remain poorly explored in green microalgae (Chlorophyta) photosynthetic organisms important for global oxygen production and carbon cycling. Their varied cell wall structures make them a useful system for studying the evolutionary origins of cell wall integrity sensing. In the present study, we employed advanced bioinformatics tools and AI-driven algorithms to map RLK distribution across 34 Chlorophyta species, characterize their structural and functional properties, and investigate their relationship with known plant counterparts. We identified 736 putative RLKs, significantly expanding the known inventory in microalgae. Structural analyses revealed a diverse array of extracellular domains, many resembling motifs associated with plant CWI sensors. These included domains linked to protein-protein interaction (e.g. LRR, PAN, ARM), cell wall remodeling (e.g. glycosyl hydrolases, lyases and carbohydrate-binding domains) and extracellular matrix mechanosensing (e.g. LPXTG, Fibronectin). This domain diversity indicates that sophisticated mechanisms for extracellular sensing and CWI monitoring may have been established early in evolution. Our findings provide valuable insights into the evolutionary diversification of RLKs and create a novel framework for future studies exploring their functional roles in algae and evolutionary links to conservation in vascular plant signaling pathways.