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Isolation of Genes from Cold Treated Poncirus trifoliata




Meng, Shasha

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Low temperature is one of the most critical environmental factors limiting plant growth and productivity. To survive, plants have developed a complex stress response system for defense against various environmental factors. The purpose of this study was to determine genetic changes in cold treated Poncirus trifoliata. The cDNA amplified fragment-length polymorphism (cDNA-AFLP) patterns of 4°C treated (cold shock), non-treated, and cold acclimated plants were compared based on differences in gene expression. Thirteen genes, isolated in this study, were grouped into five classes based on their expression patterns in cold acclimation and in 4°C treatment. Class I contains six genes confirmed as up-regulated in cold acclimated Poncirus only. They are: S7, homologue of a UDP-glycosyltransferase (UGT) from Arabidopsis thaliana; S47, homologue of a trehalose-6-phosphate synthase (TPS) from Arabidopsis thaliana; S126, homologue of a chalcone-flavanone isomerase family protein from Oryza sativa (japonica cultivar-group); S159, homologue of a cinnamate 4-hydroxylase (C4H) CYP73 from Citrus sinensis; S160B, homologue of a formin-like protein AHF1 from Arabidopsis thaliana; S176, homologue of a putative serine carboxypeptidase (Ser-CP) from Medicago truncatula. Class II contains one gene which was confirmed as down-regulated in cold acclimated plants: S8, homologue of a putative syntaxin of plants 52 (SYP52) from Oryza sativa and a syntaxin of plants 51 (SYP51) from Arabidopsis thaliana. Class III contains four genes confirmed as up-regulated upon 55 h of cold treatment at 4°C: S17, homologue to a MAPK 3 from Chorispora bungeana; S53, homologue to the calcium ion binding site of a mannosyl-oligosaccharide 1, 2-alpha-mannosidase from Arabidopsis thaliana; S145, homologue to a TGA-type basic leucine zipper protein TGA2.1 from Phaseolus vulgaris; S149, homologue to a putative senescence-associated protein from Pyrus communis. Class IV contains one gene confirmed as up-regulated in Poncirus under both cold acclimation and 55 h of cold treatment at 4°C, which is S3, homologue of an auxin and ethylene responsive GH3-like protein from Capsicum chinense and an Nt-gh3 deduced protein from Nicotiana tabacum. Class V containing one gene confirmed as up-regulated in 55 h cold treatment at 4°C but as down-regulated upon cold acclimation, S134, homologue of a phosphoenolpyruvate carboxykinase (PEPC) from Arabidopsis thaliana. Genes isolated in this study and others were divided into five groups based on their function: group I, genes involved in signal transduction and regulation of gene expression; group II, genes involved in protein synthesis; group III, genes involved in osmotic stress response; group IV, genes involved in oxidative stress; group V, genes involved in cell skeleton reorganization, vesicle trafficking and cell senescence.