ALA6, a P4-type ATPase, Is Involved in Heat Stress Responses in Arabidopsis thaliana.

Yue Niu,Dongshi Wan,Baiyun Liu,Jianchao Ma,Xinyu Wang,Yun Xiang,Dong Qian,Wenliang He

doi:10.3389/fpls.2017.01732

Abstract

Maintaining lipid membrane integrity is an essential aspect of plant tolerance to high temperature. P4-type ATPases are responsible for flipping and stabilizing asymmetric phospholipids in membrane systems, though their functions in stress tolerance are not entirely clear. Aminophospholipid ATPase6 (ALA6) is a member of the P4-type ATPase family, which has 12 members in Arabidopsis thaliana. Here, we show that a loss-of-function mutant of ALA6 (ala6) exhibits clear sensitivity to heat stress, including both basal and acquired thermotolerance treatments. Overexpression of ALA6 improves seedling resistance to heat stress, while mutated ALA6 transgenic plants, in which the conserved functional site of the ALA family has a point mutation, are still susceptible to heat stress like ala6 loss-of-function mutant. In addition, ala6 displays higher ion-leakage during heat treatment, suggesting that the lipid flippase activity of ALA6 plays a vital role in heat stress responses. Transcriptome analysis reveals differences in gene expression between ala6 and wild-type plants with or without heat stress. The differentially expressed genes are involved primarily in the physiological processes of stress response, cellular compartment maintenance, macromolecule stability and energy production. Our results suggest that ALA6 is crucial for the stability of membrane when plants suffer from high temperature stress.

Highlights

The phospholipid bilayer of cell membranes is asymmetrical, as the abundance of various lipid species on one side differs from that on the other
The T-DNA insertion mutant used in this experiment was ala6 (SALK_150173), obtained from the Arabidopsis Biological Resource Center (Ohio State University1) with homozygous progeny determined via Polymerase chain reaction (PCR) screening (Alonso et al, 2003)
Gene expressed in different tissues via semi RT-PCR analysis showed that Aminophospholipid ATPase6 (ALA6) was expressed in reproductive organs more than that in vegetative tissues (Figure 1B)

Summary

Introduction

The phospholipid bilayer of cell membranes is asymmetrical, as the abundance of various lipid species on one side differs from that on the other. The positions of the phospholipids are not fixed. Phospholipids perform multiple intramolecular motions, including rotation and lateral diffusion, and can flip-flop between the two leaflets (Pomorski and Menon, 2016). The ambient temperature has a direct effect on the rate and frequency of these movements, eventually altering membrane fluidity. ALA6 Participates in Heat-Stress Responses membrane is vital for cell function, especially during abrupt temperature changes (Murata and Los, 1997; Vigh et al, 1998, 2007; Horváth et al, 2012) Maintenance of the thermodynamic balance of the Abbreviations: AGP, Arabinogalactan protein; AOC, Allene oxide cyclase; BBX, B-box domain protein; Chl, Chlorophyll; DEG, Differentially expressed gene; EL, Electrolyte leakage; ERF, Ethylene response factor; FPKM, Fragments per kilobase of transcript per million fragments mapped; GUS, β-Glucuronidase; HSP, Heat shock protein; JA, Jasmonic acid; MGDG, Monogalactosyldiacylglycerol; PC, Phosphatidylcholine; PCR, Polymerase chain reaction; PE, Phosphatidylethanolamine; PS, Phosphatidylserine; PSII, Photosystem II; SLAH, Slow anion channel-associated homolog; UBQ, Ubiquitin; WRKY, Transcription factor with conserved amino acid sequence WRKYGQK.

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Conclusion