SummaryPhospholipase D (PLD), which hydrolyses phospholipids to produce phosphatidic acid, has been implicated in plant response to macronutrient availability in Arabidopsis. This study investigated the effect of increased PLDe expression on nitrogen utilization in Brassica napus to explore the application of PLDe manipulation to crop improvement. In addition, changes in membrane lipid species in response to nitrogen availability were determined in the oil seed crop. Multiple PLDe over expression (PLDe-OE) lines displayed enhanced biomass accumulation under nitrogendeficient and nitrogen-replete conditions. PLDe-OE plants in the field produced more seeds than wild-type plants but have no impact on seed oil content. Compared with wild-type plants, PLDe-OE plants were enhanced in nitrate transporter expression, uptake and reduction, whereas the activity of nitrite reductase was higher under nitrogen-depleted, but not at nitrogen-replete conditions. The level of nitrogen altered membrane glycerolipid metabolism, with greater impacts on young than mature leaves. The data indicate increased expression of PLDe has the potential to improve crop plant growth and production under nitrogen-depleted and nitrogenreplete conditions.

SUMMARY Autophagy delivers cellular cargoes for degradation and plays an important role in nutrient recycling under nutrient limitation. A critical component in autophagy is the lipidation of phosphatidylethanolamine (PE) to autophagy‐related protein 8 (ATG8) to form ATG8‐PE. Here we show that phospholipase Dε (PLDε) in Arabidopsis cells interacts with ATG8 and hydrolyzes ATG8‐PE conjugates. In response to nitrogen deficiency, the transcript and protein levels of PLDε increase and additionally, an increasing amount of PLDε became associated with intracellular membranes compared with its primary plasma membrane association under sufficient nitrogen in Arabidopsis seedlings. PLDε‐knockout (KO) plants have a lower number, whereas PLDε‐overexpressing (OE) plants have a higher number of autophagosomes than that in wild‐type plants during nitrogen starvation. The level of ATG8‐PE is lower in PLDε‐KO, but higher in PLDε‐OE plants than in wild‐type plants. PLDε‐KO and PLDε‐OE Arabidopsis seedlings display accelerated and delayed leaf senescence, respectively, during nitrogen limitation. The results suggest that PLDε promotes autophagy in the plant response to nitrogen deficiency. The multifaceted effects of PLDε activity and interaction with ATG8 on autophagic processes are discussed.

Patatin-related phospholipases (pPLAs) are acyl-hydrolyzing enzymes implicated in various processes, including lipid metabolism, signal transduction, plant growth and stress responses, but the function for many specific pPLAs in plants remains unknown. Here we determine the effect of patatin-related phospholipase A pPLAIIIγ on Arabidopsis response to abiotic stress. Knockout of pPLAIIIγ rendered plants more sensitive whereas overexpression of pPLAIIIγ enhanced plant tolerance to NaCl and drought in seed germination and seedling growth. The pPLAIIIγ-knockout and overexpressing seedlings displayed a lower and higher level of lysolipids and free fatty acids than that of wild-type plants in response to NaCl stress, respectively. These results indicate that pPLAIIIγ acts a positive regulator of salt and osmatic stress tolerance in Arabidopsis.

Molybdenum (Mo), which is an essential microelement for plant growth, plays important roles in multiple metabolic and physiological processes, including responses to drought and cold stress in wheat. Lipids also have crucial roles in plant adaptions to abiotic stresses. The aim of this study was to use glycerolipidomic and transcriptomic analyses to determine the changes in lipids induced by Mo that are associated with Mo-enhanced drought tolerance in wheat. Mo treatments increased the transcript levels of genes involved in fatty acid and glycerolipid biosynthesis and desaturation, but suppressed the expression of genes involved in oxylipin production. Wheat plants supplemented with Mo displayed higher contents of monogalactosyldiacyglycerol (MGDG), digalactosyldoacylglycerol (DGDG), phosphatidylglycerol (PG), phosphatidylethanolamine (PE), and phosphatidylcholine (PC) with increased levels of unsaturation. The levels of MGDG, DGDG, PG, and PC increased under PEG-simulated drought (PSD), and the magnitude of the responses varied in the presence and absence of Mo. Mo increased the accumulation of the most abundant glycerolipid species of C36:6, C34:4, and C34:3 by increasing the expression of genes related to desaturation under PSD, and this contributed to maintaining the fluidity of membranes. In addition, Mo attenuated the decreases in the ratios of DGDG/MGDG and PC/PE that were observed under PSD. These changes in lipids in Mo-treated wheat would contribute to maintaining the integrity of membranes and to protecting the photosynthetic apparatus, thus acting together to enhance drought tolerance.