Phospholipase Dε interacts with autophagy‐related protein 8 and promotes autophagy in Arabidopsis response to nitrogen deficiency

Abstract

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.

Effects of Phospholipase Dε Overexpression on Soybean Response to Nitrogen and Nodulation

“…Among 12 PLDs in Arabidopsis, only PLDε was found to be involved in N deficiency response (Hong et al, 2009), and its expression increased in response to N deficiency (Yao et al, 2022). In this study, the expression of soybean PLDε1 and PLDε2 was induced by nitrogen starvation.…”

“…Particularly, overexpression (OE) of PLDε enhanced growth under N deficiency in Arabidopsis (Hong et al, 2009) and canola (Lu et al, 2016). Our recent results indicate that one mechanism by which PLDε enhances Arabidopsis growth is via its interaction with and promotion of autophagy to promote N recycling (Yao et al, 2022). Thus, PLDε could be one target for enhancing plant growth under limited N conditions.…”

Phosphatidic Acid in Plant Hormonal Signaling: From Target Proteins to Membrane Conformations

“…For example, under nutrient limitation, cells induce autophagy that delivers cellular cargoes for degradation as a part of the nutrient recycling mechanism. The role of PA in plant autophagy could be inferred from data on plant [ 145 ] and animal [ 146 ] systems. In Arabidopsis , At PLDε has been found to promote autophagy in plant response to nitrogen deficiency.…”

“…Physiological analysis indicates that At PLDε acts to delay senescence in response to nitrogen deficiency. The transcript level of At PLDε was increased in these stress conditions, while analysis of At PLDε-GFP cellular distribution indicated that nitrate starvation increased protein levels of At PLDε [ 145 ] and promoted its association with intracellular membranes. Co-immunoprecipitation and bimolecular fluorescence complementation analysis indicate that At PLDε interacts with At ATG8, an autophagy-related protein that is essential for the biogenesis, cargo recruitment and maturation of autophagosomes.…”

“…Genetic analysis of GFP-AtATG8-labeled At PLDε-mutated plants demonstrated that At PLDε promotes autophagosome formation in response to nitrogen deprivation. Monitoring of the levels of At ATG1a and At NBR1 (NEIGHBOR OF BRCA1) proteins that are known to be degraded by autophagy under stress suggested that At PLDε increases their autophagic degradation under nitrogen deficiency [ 145 ]. Therefore, PLD and PA could play a multifaced role in plant autophagy.…”