Target of Rapamycin is involved in root hair development in Phaseolus vulgaris.

Abstract

Root hairs are essential for nutrient acquisition and rhizosphere interactions in vascular plants. While the Target of Rapamycin (TOR) kinase is a well established regulator of growth and metabolism, its role in root hair development in Phaseolus vulgaris remains underexplored. In this study, we investigated the role of TOR in root hair morphogenesis using RNA interference (RNAi)-mediated downregulation of PvTOR and transcriptomic profiling. Microscopic examination of PvTOR-RNAi roots confirmed significant reductions in root hair length and density. Transcriptomic analysis revealed differential expression of 148 P. vulgaris homologs of Arabidopsis thaliana root hair-related genes, with 63 genes downregulated and 85 upregulated. Gene Ontology enrichment analysis indicated that these differentially expressed genes (DEGs) were primarily involved in cellular development, cell differentiation, and redox regulation. Upregulation of phosphoinositide metabolism genes, ROS generators, and cell wall-related extensins suggests compensatory tip growth responses under TOR suppression. On the otherhand, repression of key auxin signaling genes and cell wall-loosening proteins such as EXPA1 and ENDOGLUCANASE5 indicates a shift away from elongation processes. Protein - protein interaction network analysis highlighted phosphoinositide and ROP GTPase signaling hubs as major pathways affected by TOR inhibition, suggesting that TOR indirectly modulates cell polarity and membrane dynamics essential for root hair development. These findings provide further evidence of TOR as a central integrator of hormonal, metabolic, and structural cues during root hair formation.