A plastidial lipoyl synthase LIP1p plays a crucial role in phosphate homeostasis in Arabidopsis

Phosphate (Pi) homeostasis is important for plant growth and adaptation to dynamic environment, which requires the precise regulation of phosphate transporter (PHT) trafficking from endoplasmic reticulum to plasma membrane. LIPOYL SYNTHASE 1p (LIP1p) is known as a key enzyme in plastids to catalyze lipoylation of pyruvate dehydrogenase complex for de novo fatty acid synthesis. It is unknown whether this process is involved in regulating Pi homeostasis. Here, we demonstrate a new role of LIP1p in controlling Pi homeostasis by regulating PHT1 trafficking. We recovered a weak mutant allele of LIP1p in Arabidopsis that accumulates much less Pi and has enhanced expression of phosphate starvation induced genes. Lipidomics analysis revealed that LIP1p mutation alters lipid profile and compromises vesicle trafficking of PHT1 to the plasma membrane to impair Pi uptake. Beside phosphorus, the homeostasis of a series of mineral nutrients was also perturbed in lip1p mutant. Our findings provide powerful genetic evidences to support the linkage between lipoylation and ion homeostasis in plant. Total RNAs were extracted from 8-day-old seedlings under HP or LP conditions using a RNeasy Plant Mini Kit (Qiagen, R415102) according to the instruction manual. Three biological replicates were performed for each genotype. The genes that were up-regulated or down-regulated with a twofold or higher change with an adjusted P value of ≤0.05 were regarded as DEGs. Venn diagrams were created using Venny (2.1.0). GO enrichment analysis was performed using clusterProfiler (v.4.0.5)(Yu et al., 2012).