Enhanced root growth in phosphate‐starved Arabidopsis by stimulating de novo phospholipid biosynthesis through the overexpression of LYSOPHOSPHATIDIC ACID ACYLTRANSFERASE 2 (LPAT2)

Abstract

Upon phosphate starvation, plants retard shoot growth but promote root development presumably to enhance phosphate assimilation from the ground. Membrane lipid remodelling is a metabolic adaptation that replaces membrane phospholipids by non-phosphorous galactolipids, thereby allowing plants to obtain scarce phosphate yet maintain the membrane structure. However, stoichiometry of this phospholipid-to-galactolipid conversion may not account for the massive demand of membrane lipids that enables active growth of roots under phosphate starvation, thereby suggesting the involvement of de novo phospholipid biosynthesis, which is not represented in the current model. We overexpressed an endoplasmic reticulum-localized lysophosphatidic acid acyltransferase, LPAT2, a key enzyme that catalyses the last step of de novo phospholipid biosynthesis. Two independent LPAT2 overexpression lines showed no visible phenotype under normal conditions but showed increased root length under phosphate starvation, with no effect on phosphate starvation response including marker gene expression, root hair development and anthocyanin accumulation. Accompanying membrane glycerolipid profiling of LPAT2-overexpressing plants revealed an increased content of major phospholipid classes and distinct responses to phosphate starvation between shoot and root. The findings propose a revised model of membrane lipid remodelling, in which de novo phospholipid biosynthesis mediated by LPAT2 contributes significantly to root development under phosphate starvation.

LYSOPHOSPHATIDIC ACID ACYLTRANSFERASES 4 and 5 are involved in glycerolipid metabolism and nitrogen starvation response in Arabidopsis

“…To investigate a possible role of LPAT3, LPAT4, and LPAT5 in the plant response to N starvation, T‐DNA‐knockout mutants were isolated for respective LPAT isoforms. The lpat3‐1 knockout mutant was reported previously (Angkawijaya et al ., ), so only the mutants for LPAT4 ( lpat4‐1 ) and LPAT5 ( lpat5‐1 ) were isolated. The T‐DNA insertion positions were confirmed to be within the first exon ( lpat4‐1 ) or second intron ( lpat5‐1 ) of the respective genes by DNA sequencing (Fig.…”

“…LPAT1 and LPAT2 have a vital role because their individual knockout causes embryonic and female gametophytic lethality, respectively (Kim & Huang, ; Yu et al ., ; Kim et al ., ). Our recent report showed an involvement of LPAT2 in stimulating de novo glycerolipid biosynthesis in Arabidopsis root to cope with phosphate starvation (Angkawijaya et al ., ). This evidence suggests that LPAT1 and LPAT2 are the primary and essential LPAT isoforms in plastid‐ and ER‐localized de novo glycerolipid biosynthesis pathways, respectively.…”

Non‐specific phospholipases C, NPC2 and NPC6, are required for root growth in Arabidopsis

“…Total lipid was extracted from leaves of 4-week-old plants as described (Nakamura et al, 2014;Angkawijaya et al, 2017). Briefly, each glycerolipid class was separated on a silica-gel thinlayer chromatography (TLC) plate with the solvent system of chloroform:methanol:aqueous ammonia = 120:80:8 (by volume) for the first dimension and chloroform:methanol:acetic acid:water = 170:20:15:3 (by volume) for the second dimension.…”

A novel glycerophosphodiester phosphodiesterase improves phosphate deficiency tolerance in rice

“…These differences became more prominent under –P conditions, which suggest an important function of OsGDPD2 in de novo glycerolipid biosynthesis. In a recent report, low Pi responsive LPAT2, an acyltransferase downstream of GDPD, has also been shown to mediate de novo lipid biosynthesis in Arabidopsis (Angkawijaya, Nguyen, & Nakamura, ). However, in our analysis, we did not find any significant change in expression of OsLPAT2 (rice homolog of Arabidopsis LPAT2 ).…”