title: Overexpression of SlGMEs leads to ascorbate accumulation with enhanced oxidative stress, cold, and salt tolerance in tomato.
abstract: GDP-Mannose 3',5'-epimerase (GME; EC 5.1.3.18) catalyses the conversion of GDP-D-mannose to GDP-L-galactose, an important step in the ascorbic acid (AsA) biosynthesis pathway in higher plants. In this study, two members of the GME gene family were isolated from tomato (Solanum lycopersicum). Both SlGME genes encode 376 amino acids and share a 92% similarity with each other. Semi-quantitative RT-PCR indicated that SlGME1 was constantly expressed in various tissues, whereas SlGME2 was differentially expressed in different tissues. Transient expression of fused SlGME1-GFP (green fluorescent protein) and SlGME2-GFP in onion cells revealed the cytoplasmic localisation of the two proteins. Transgenic plants over-expressing SlGME1 and SlGME2 exhibited a significant increase in total ascorbic acid in leaves and red fruits compared with wild-type plants. They also showed enhanced stress tolerance based on less chlorophyll content loss and membrane-lipid peroxidation under methyl viologen (paraquat) stress, higher survival rate under cold stress, and significantly higher seed germination rate, fresh weight, and root length under salt stress. The present study demonstrates that the overexpression of two members of the GME gene family resulted in increased ascorbate accumulation in tomato and improved tolerance to abiotic stresses.
authors.affiliation: The National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Chanjuan
authors.initials: C
authors.lastname: Zhang
authors.forename: Junxia
authors.initials: J
authors.lastname: Liu
authors.forename: Yuyang
authors.initials: Y
authors.lastname: Zhang
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Cai
authors.forename: Pengjuan
authors.initials: P
authors.lastname: Gong
authors.forename: Junhong
authors.initials: J
authors.lastname: Zhang
authors.forename: Taotao
authors.initials: T
authors.lastname: Wang
authors.forename: Hanxia
authors.initials: H
authors.lastname: Li
authors.forename: Zhibiao
authors.initials: Z
authors.lastname: Ye
mesh_terms: D000595:Amino Acid Sequence; D001205:Ascorbic Acid / Q000096:biosynthesis*; D002238:Carbohydrate Epimerases / Q000235:genetics / Q000378:metabolism*; D002734:Chlorophyll / Q000032:analysis; D003080:Cold Temperature; D005638:Fruit / Q000378:metabolism; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D018525:Germination; D015227:Lipid Peroxidation; D018551:Solanum lycopersicum / Q000201:enzymology / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008969:Molecular Sequence Data; D018384:Oxidative Stress / Q000235:genetics*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D055051:Salt-Tolerant Plants / Q000235:genetics* / Q000502:physiology; D012965:Sodium Chloride / Q000494:pharmacology
chemical_list: D010940:Plant Proteins; D002734:Chlorophyll; D012965:Sodium Chloride; D002238:Carbohydrate Epimerases; C019192:GDPmannose 3,5-epimerase; D001205:Ascorbic Acid