Phospholipase D‐derived phosphatidic acid promotes root hair development under phosphorus deficiency by suppressing vacuolar degradation of PIN‐FORMED2

De‐Li Lin,Wen‐Ming Zheng,Hong‐Wei Xue,Zhi‐Hong Xu,Jin‐Fang Tan,Li‐Hua Jia,Hong‐Yan Yao

doi:10.1111/nph.16330

Abstract

Summary Root hair development is crucial for phosphate absorption, but how phosphorus deficiency affects root hair initiation and elongation remains unclear.We demonstrated the roles of auxin efflux carrier PIN‐FORMED2 (PIN2) and phospholipase D (PLD)‐derived phosphatidic acid (PA), a key signaling molecule, in promoting root hair development in Arabidopsis thaliana under a low phosphate (LP) condition.Root hair elongation under LP conditions was greatly suppressed in pin2 mutant or under treatment with a PLDζ2‐specific inhibitor, revealing that PIN2 and polar auxin transport and PLDζ2‐PA are crucial in LP responses. PIN2 was accumulated and degraded in the vacuole under a normal phosphate (NP) condition, whereas its vacuolar accumulation was suppressed under the LP or NP plus PA conditions. Vacuolar accumulation of PIN2 was increased in pldζ2 mutants under LP conditions. Increased or decreased PIN2 vacuolar accumulation is not observed in sorting nexin1 (snx1) mutant, indicating that vacuolar accumulation of PIN2 is mediated by SNX1 and the relevant trafficking process. PA binds to SNX1 and promotes its accumulation at the plasma membrane, especially under LP conditions, and hence promotes root hair development by suppressing the vacuolar degradation of PIN2.We uncovered a link between PLD‐derived PA and SNX1‐dependent vacuolar degradation of PIN2 in regulating root hair development under phosphorus deficiency.

Highlights

Pi is an essential macronutrient that plays a crucial role in multiple physiological processes and metabolic pathways in plants
Since the auxin efflux carrier PIN2 plays crucial roles in root hair development, we investigated whether polar auxin transport is involved in altered root hair growth under low phosphate (LP) conditions, as well as the underlying regulatory mechanism
By using a specific nutrient system, studies revealed that root hair length and numbers are significantly increased in the wild-type (WT) under LP conditions (Fig. 1a,b), whereas these responses were almost completely disrupted in the Arabidopsis pin2 mutant; in particular, the root hair length was greatly reduced (Fig. 1a)

Summary

Introduction

Pi is an essential macronutrient that plays a crucial role in multiple physiological processes and metabolic pathways in plants. Pi availability is a major factor limiting crop production. In Arabidopsis thaliana, Pi deficiency inhibits root apical meristem activity through reduced cell division and the loss of a quiescent center, while inducing lateral root formation and growth (Sanchez-Calderon et al, 2005). PLDf2 and NPC4 play distinct roles in root hair growth and development in response to Pi deprivation: PLDf2 negatively modulates root hair density and length, whereas NPC4 promotes root hair elongation (Su et al, 2018). PLDf2 and its product, phosphatidic acid (PA), function in root growth and auxin responses by regulating the cycling of the auxin efflux carrier

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