GSTU43 gene involved in ALA-regulated redox homeostasis, to maintain coordinated chlorophyll synthesis of tomato at low temperature

Tao Liu,Xiaohui Hu,Jianyu Yang,Jianming Li,Qingjie Du,Suzhi Li,Xiaojing Li,Jiaojiao Xu,Pengxiang Chen

doi:10.1186/s12870-019-1929-1

Abstract

BackgroundExogenous 5-aminolevulinic acid (ALA) positively regulates plants chlorophyll synthesis and protects them against environmental stresses, although the protection mechanism is not fully clear. Here, we explored the effects of ALA on chlorophyll synthesis in tomato plants, which are sensitive to low temperature. We also examined the roles of the glutathione S-transferase (GSTU43) gene, which is involved in ALA-induced tolerance to oxidation stress and regulation of chlorophyll synthesis under low temperature.ResultsExogenous ALA alleviated low temperature caused chlorophyll synthesis obstacle of uroporphyrinogen III (UROIII) conversion to protoporphyrin IX (Proto IX), and enhanced the production of chlorophyll and its precursors, including endogenous ALA, Proto IX, Mg-protoporphyrin IX (Mg-proto IX), and protochlorophyll (Pchl), under low temperature in tomato leaves. However, ALA did not regulate chlorophyll synthesis at the level of transcription. Notably, ALA up-regulated the GSTU43 gene and protein expression and increased GST activity. Silencing of GSTU43 with virus-induced gene silencing reduced the activities of GST, superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase, and increased the membrane lipid peroxidation; while fed with ALA significant increased all these antioxidase activities and antioxidant contents, and alleviated the membrane damage.ConclusionsALA triggered GST activity encoded by GSTU43, and increased tomato tolerance to low temperature-induced oxidative stress, perhaps with the assistance of ascorbate- and/or a glutathione-regenerating cycles, and actively regulated the plant redox homeostasis. This latter effect reduced the degree of membrane lipid peroxidation, which was essential for the coordinated synthesis of chlorophyll.

Highlights

Exogenous 5-aminolevulinic acid (ALA) positively regulates plants chlorophyll synthesis and protects them against environmental stresses, the protection mechanism is not fully clear
Our preliminary studies showed that ALA induced early Hydrogen peroxide (H2O2) signaling under normal conditions, which interacted with JA, induced the downstream NO, regulated the redox state, resulting in elevated antioxidant capacity and photosynthesis in tomato plants under low temperature [12, 34]
We further explored whether GSTU43 involved in ALA-mediated redox status and alleviation of membrane lipid peroxidation, which was crucial for the coordinated chlorophyll synthesis

Summary

Introduction

Exogenous 5-aminolevulinic acid (ALA) positively regulates plants chlorophyll synthesis and protects them against environmental stresses, the protection mechanism is not fully clear. Plants exposed to low temperature exhibit a short-term stress response involved modification of gene expression and levels of plant hormones, increased cross-talk signaling, and accumulation of osmolytes and antioxidants, It is well-known that exogenous application of 5-aminolevulinic acid (ALA) improves plant tolerance to environmental stress [3,4,5,6,7,8,9]. This compound is the precursor to porphyrins, which are, in turn, the precursors to plant pigments, including heme and chlorophyll; as such, application of ALA increased the chlorophyll content of plants [8, 10, 11]. GSTs have catalytic functions and non-catalytic functions (such as binding and transport of secondary metabolites and hormones), which related to their structural dynamics [19]

Methods

Results

Discussion

Conclusion