Lysophosphatidylcholine homeostasis via the Lands cycle regulates root growth in Arabidopsis

Lysophosphatidylcholine acyltransferase (LPCAT) is a key enzyme of the Lands cycle that remodels phosphatidylcholine (PC). Proper balance between lysophosphatidylcholine (LPC) and PC is essential for phospholipid turnover and membrane homeostasis. Here, we show that the Arabidopsis lpcat double mutant exhibits an altered LPC/PC ratio in root tissues, reflecting a compromised Lands cycle. Using a chemical phenocopying strategy, we found that root growth of the lpcat mutant was more sensitive than that of wild type to lysoPAF, a structural analog of LPC. This defect was largely rescued when lysoPAF treatment was combined with ONO-RS-082, a phospholipase A2 (PLA2) inhibitor. Subcellular localization experiments with GFP fusions demonstrated that both LPCAT1 and LPCAT2 are targeted to the endoplasmic reticulum (ER) membrane. Furthermore, RNA-seq analysis of root tissues revealed transcriptional changes indicative of ER stress and altered endomembrane trafficking. Together, our results demonstrate that ER-localized LPCAT plays a pivotal role in maintaining root growth integrity when plants encounter conditions that require adjustments in lipid homeostasis. The likely role of ER localized LPCAT in modulating ER stress and root growth will be discussed.