Manipulation of the rice L-galactose pathway: evaluation of the effects of transgene overexpression on ascorbate accumulation and abiotic stress tolerance.
Ascorbic acid (AsA) is the most abundant water-soluble antioxidant in plants, and it plays a crucial role in plant growth, development and abiotic stress tolerance. In the present study, six key Arabidopsis or rapeseed genes involved in AsA biosynthesis were constitutively overexpressed in an elite Japonica rice cultivar. These genes encoded the GDP-mannose pyrophosphorylase (GMP), GDP-mannose-3',5'-epimerase (GME), GDP-L-galactose phosphorylase (GGP), L-galactose-1-phosphate phosphatase (GPP), L-galactose dehydrogenase (GDH), and L-galactono-1,4-lactone dehydrogenase (GalLDH). The effects of transgene expression on rice leaf AsA accumulation were carefully evaluated. In homozygous transgenic seedlings, AtGGP transgenic lines had the highest AsA contents (2.55-fold greater than the empty vector transgenic control), followed by the AtGME and AtGDH transgenic lines. Moreover, with the exception of the AtGPP lines, the increased AsA content also provoked an increase in the redox state (AsA/DHA ratio). To evaluate salt tolerance, AtGGP and AtGME transgenic seedlings were exposed to salt stress for one week. The relative plant height, root length and fresh weight growth rates were significantly higher for the transgenic lines compared with the control plants. Altogether, our results suggest that GGP may be a key rate-limiting step in rice AsA biosynthesis, and the plants with elevated AsA contents demonstrated enhanced tolerance for salt stress.
Key Laboratory of Crop Genetics and Physiology of Jiangsu Province, Co-Innovation Center for Modern Production Technology of Grain Crops, Yangzhou University, Yangzhou 225009, Jiangsu, China; Agricultural Science Institute of Coastal Region of Jiangsu, Yancheng 224002, Jiangsu, China.
Gui-Yun
GY
Zhang
Key Laboratory of Crop Genetics and Physiology of Jiangsu Province, Co-Innovation Center for Modern Production Technology of Grain Crops, Yangzhou University, Yangzhou 225009, Jiangsu, China.
Ru-Ru
RR
Liu
Key Laboratory of Crop Genetics and Physiology of Jiangsu Province, Co-Innovation Center for Modern Production Technology of Grain Crops, Yangzhou University, Yangzhou 225009, Jiangsu, China.
Chang-Quan
CQ
Zhang
School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, China.
Ke-Xuan
KX
Tang
Agricultural Science Institute of Coastal Region of Jiangsu, Yancheng 224002, Jiangsu, China.
Ming-Fa
MF
Sun
Agricultural Science Institute of Coastal Region of Jiangsu, Yancheng 224002, Jiangsu, China.
Guo-Hong
GH
Yan
Key Laboratory of Crop Genetics and Physiology of Jiangsu Province, Co-Innovation Center for Modern Production Technology of Grain Crops, Yangzhou University, Yangzhou 225009, Jiangsu, China.
Qiao-Quan
QQ
Liu
D001205:Ascorbic Acid / Q000378:metabolism; D005690:Galactose / Q000378:metabolism*; D015870:Gene Expression; D006720:Homozygote; D053858:Metabolic Networks and Pathways; D012275:Oryza / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D010084:Oxidation-Reduction; D018515:Plant Leaves / Q000378:metabolism; D030821:Plants, Genetically Modified; D055049:Salt Tolerance / Q000235:genetics; D013312:Stress, Physiological; D019076:Transgenes
D001205:Ascorbic Acid; D005690:Galactose