The enhancement of tolerance to salt and cold stresses by modifying the redox state and salicylic acid content via the cytosolic malate dehydrogenase gene in transgenic apple plants

Abstract

SummaryIn this study, we characterized the role of an apple cytosolic malate dehydrogenase gene (MdcyMDH) in the tolerance to salt and cold stresses and investigated its regulation mechanism in stress tolerance. The MdcyMDH transcript was induced by mild cold and salt treatments, and MdcyMDH‐overexpressing apple plants possessed improved cold and salt tolerance compared to wild‐type (WT) plants. A digital gene expression tag profiling analysis revealed that MdcyMDH overexpression largely altered some biological processes, including hormone signal transduction, photosynthesis, citrate cycle and oxidation–reduction. Further experiments verified that MdcyMDH overexpression modified the mitochondrial and chloroplast metabolisms and elevated the level of reducing power, primarily caused by increased ascorbate and glutathione, as well as the increased ratios of ascorbate/dehydroascorbate and glutathione/glutathione disulphide, under normal and especially stress conditions. Concurrently, the transgenic plants produced a high H2O2 content, but a low O2·− production rate was observed compared to the WT plants. On the other hand, the transgenic plants accumulated more free and total salicylic acid (SA) than the WT plants under normal and stress conditions. Taken together, MdcyMDH conferred the transgenic apple plants a higher stress tolerance by producing more reductive redox states and increasing the SA level; MdcyMDH could serve as a target gene to genetically engineer salt‐ and cold‐tolerant trees.

Improvement of drought tolerance by overexpressing MdATG18a is mediated by modified antioxidant system and activated autophagy in transgenic apple

“…Strong maintenance of a reduced AsA state might be due to the high expression levels of MDHAR and DHAR , which are involved in AsA recycling (Conklin and Barth, ). This drought tolerance improvement by MdATG18a overexpression is in accordance with a recent report about transgenic apple plants overexpressing MdcyMDH , which show greater tolerance to salt and cold stresses because the redox state is modified by increases in AsA and GSH levels as well as a reduction in their oxidized ratios (Wang et al ., ). Drought‐related damage is presumably modulated in MdATG18a transgenic plants because of improvements in their antioxidant systems.…”

“…Autophagy, a conserved cellular process in eukaryotes, plays an important role in recycling nutrients and cytoplasmic components, as well as in conferring tolerance to biotic and abiotic stresses (Han et al, 2015;Hav e et al, 2016;Mizushima and Komatsu, 2011;Ryabovol and Minibayeva, 2016;Wang et al, 2016Wang et al, , 2015bXiong et al, 2005). In the cells of plants that undergo starvation or other stresses, production of doublemembrane structures, the autophagosomes, is induced.…”

Excess Copper-Induced Alterations of Protein Profiles and Related Physiological Parameters in Citrus Leaves

“…cyMDH plays a key role in the transport of chloroplast or mitochondria NADPH to other cell compartments. Transgenic apple plants overexpressing an apple cyMDH gene displayed a higher stress-tolerance accompanied by increased reducing power, as indicated by increased concentrations of ASC and reduced glutathione (GSH) and ratios of ASC/dehydroascorbate (DHA), GSH/GSSG and NAD(P)H/NAD(P) + [44]. Thus, the Cu-toxicity-induced increases of cyMDH abundances in C. grandis leaves might be an adaptive strategy.…”

The mitochondrial alternative oxidase from Chlamydomonas reinhardtii enables survival in high light

“…Once in the cytosol, triose-P could be converted to acetyl-CoA, which is a substrate of the TCA cycle. Hence, the shuttles appear to facilitate trafficking of metabolites and electrons among the different organelles, which may be reflected by an increase in ETR and reducing power observed when cytosolic MDH was overexpressed in apple cells (91). In addition to the shuttling of reducing equivalents, chloroplast ATP antiporters and mitochondria ATP carriers have been characterized in vascular plants (92,93) and identified in C. reinhardtii (21).…”