title: PtrBAM1, a β-amylase-coding gene of Poncirus trifoliata, is a CBF regulon member with function in cold tolerance by modulating soluble sugar levels.
abstract: β-Amylase (BAM) catalyses starch breakdown to generate maltose, which can be incorporated into sugar metabolism. However, the role of BAM genes in cold tolerance is less characterized. In this study, we report the isolation and functional characterization of a chloroplast-localizing BAM-encoding gene PtrBAM1 from Poncirus trifoliata. PtrBAM1 was induced by cold, dehydration and salt, but repressed by maltose. Overexpression of PtrBAM1 in tobacco (Nicotiana nudicaulis) increased BAM activity, promoted starch degradation and enhanced the contents of maltose and soluble sugars, whereas opposite changes were observed when PtrBAM1 homolog in lemon (Citrus lemon) was knocked down. The tobacco overexpressing lines exhibited enhanced tolerance to cold at chilling or freezing temperatures. Under cold stress, higher BAM activity and greater accumulation of maltose and soluble sugars were observed in the overexpressing lines when compared with the wild-type or empty vector transformants. Bioinformatics analysis demonstrated that PtrBAM1 promoter contained a CBF-recognizing element. Yeast one-hybrid assay demonstrated that PtrCBF could interact with the promoter fragment containing the element. Taken together, these results demonstrate that PtrBAM1 is a member of CBF regulon and plays an important role in cold tolerance by modulating the levels of soluble sugars acting as osmolytes or antioxidants.
authors.affiliation: Key Laboratory of Horticultural Plant Biology (MOE), College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan, 430070, China; National Navel Orange Engineering Research Center, College of Navel Orange, Gannan Normal University, Ganzhou, 341000, China.
authors.forename: Ting
authors.initials: T
authors.lastname: Peng
authors.forename: Xiaofang
authors.initials: X
authors.lastname: Zhu
authors.forename: Nian
authors.initials: N
authors.lastname: Duan
authors.forename: Ji-Hong
authors.initials: JH
authors.lastname: Liu
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics*; D000595:Amino Acid Sequence; D002241:Carbohydrates / Q000032:analysis*; D003080:Cold Temperature; D004573:Electrolytes / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D008315:Malondialdehyde / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D032104:Poncirus / Q000201:enzymology* / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D034622:RNA Interference; D017382:Reactive Oxygen Species / Q000378:metabolism; D018085:Regulon / Q000235:genetics*; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D012995:Solubility; D013213:Starch / Q000378:metabolism; D013347:Subcellular Fractions / Q000201:enzymology; D014026:Nicotiana / Q000235:genetics; D001614:beta-Amylase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
chemical_list: D002241:Carbohydrates; D004573:Electrolytes; D010940:Plant Proteins; D017382:Reactive Oxygen Species; D008315:Malondialdehyde; D013213:Starch; D001614:beta-Amylase
keywords: antioxidant; cold stress; osmolyte; starch degradation