Fine mapping of the BnaC04.BIL1 gene controlling plant height in Brassica napus L.

BACKGROUND: Plant height is an important architecture trait which is a fundamental yield-determining trait in crops. Variety with dwarf or semi-dwarf phenotype is a major objective in the breeding because dwarfing architecture can help to increase harvest index, increase planting density, enhance lodging resistance, and thus be suitable for mechanization harvest. Although some germplasm or genes associated with dwarfing plant type have been carried out. The molecular mechanisms underlying dwarfism in oilseed rape (Brassica napus L.) are poorly understood, restricting the progress of breeding dwarf varieties in this species. Here, we report a new dwarf mutant Bndwarf2 from our B. napus germplasm. We studied its inheritance and mapped the dwarf locus BnDWARF2. RESULTS: The inheritance analysis showed that the dwarfism phenotype was controlled by one semi-dominant gene, which was mapped in an interval of 787.88 kb on the C04 chromosome of B. napus by Illumina Brassica 60 K Bead Chip Array. To fine-map BnDWARF2, 318 simple sequence repeat (SSR) primers were designed to uniformly cover the mapping interval. Among them, 15 polymorphic primers that narrowed down the BnDWARF2 locus to 34.62 kb were detected using a F2:3 family population with 889 individuals. Protein sequence analysis showed that only BnaC04.BIL1 (BnaC04g41660D) had two amino acid residues substitutions (Thr187Ser and Gln399His) between ZS11 and Bndwarf2, which encoding a GLYCOGEN SYNTHASE KINASE 3 (GSK3-like). The quantitative real-time PCR (qRT-PCR) analysis showed that the BnaC04.BIL1 gene expressed in all tissues of oilseed rape. Subcellular localization experiment showed that BnaC04.BIL1 was localized in the nucleus in tobacco leaf cells. Genetic transformation experiments confirmed that the BnaC04.BIL1 is responsible for the plant dwarf phenotype in the Bndwarf2 mutants. Overexpression of BnaC04.BIL1 reduced plant height, but also resulted in compact plant architecture. CONCLUSIONS: A dominant dwarfing gene, BnaC04.BIL1, encodes an GSK3-like that negatively regulates plant height, was mapped and isolated. Our identification of a distinct gene locus may help to improve lodging resistance in oilseed rape.

Ectopic expression of NnPER1, a Nelumbo nucifera 1-cysteine peroxiredoxin antioxidant, enhances seed longevity and stress tolerance in Arabidopsis.

Seed longevity, the maintenance of viability during storage, is a major factor for conservation of genetic resources and biodiversity. Seed longevity is an important trait of agriculture crop and is impaired by reactive oxygen species (ROS) during seed desiccation, storage and germination (C. R. Biol., 331, 2008 and 796). Seeds possess a wide range of systems (protection, detoxification, repair) allowing them to survive during storage and to preserve a high germination ability. In many plants, 1-cys peroxiredoxin (1-Cys Prx, also named PER1) is a seed-specific antioxidant which eliminates ROS with cysteine residues. Here we identified and characterized a seed-specific PER1 protein from seeds of sacred lotus (Nelumbo nucifera Gaertn.). Purified NnPER1 protein protects DNA against the cleavage by ROS in the mixed-function oxidation system. The transcription and protein accumulation of NnPER1 increased during seed desiccation and imbibition and under abiotic stress treatment. Ectopic expression of NnPER1 in Arabidopsis enhanced the seed germination ability after controlled deterioration treatment (CDT), indicating that NnPER1 improves seed longevity of transgenic plants. Consistent with the function of NnPER1 on detoxifying ROS, we found that the level of ROS release and lipid peroxidation was strikingly lower in transgenic seeds compared to wild-type with or without CDT. Furthermore, transgenic Arabidopsis seeds ectopic-expressing NnPER1 displayed enhanced tolerance to high temperature and abscisic acid (ABA), indicating that NnPER1 may participate in the thermotolerance and ABA signaling pathway.

Overexpression of Nelumbo nucifera metallothioneins 2a and 3 enhances seed germination vigor in Arabidopsis.

Metallothioneins (MTs) are small, cysteine-rich and metal-binding proteins which are involved in metal homeostasis and scavenging of reactive oxygen species. Although plant MTs have been intensively studied, their roles in seeds remain to be clearly established. Here, we report the isolation and characterization of NnMT2a, NnMT2b and NnMT3 from sacred lotus (Nelumbo nucifera Gaertn.) and their roles in seed germination vigor. The transcripts of NnMT2a, NnMT2b and NnMT3 were highly expressed in developing and germinating sacred lotus seeds, and were dramatically up-regulated in response to high salinity, oxidative stresses and heavy metals. Analysis of transformed Arabidopsis protoplasts showed that NnMT2a-YFP and NnMT3-YFP were localized in cytoplasm and nucleoplasm. Transgenic Arabidopsis seeds overexpressing NnMT2a and NnMT3 displayed improved resistance to accelerated aging (AA) treatment, indicating their significant roles in seed germination vigor. These transgenic seeds also exhibited higher superoxide dismutase activity compared to wild-type seeds after AA treatment. In addition, we showed that NnMT2a and NnMT3 conferred improved germination ability to NaCl and methyl viologen on transgenic Arabidopsis seeds. Taken together, these data demonstrate that overexpression of NnMT2a and NnMT3 in Arabidopsis significantly enhances seed germination vigor after AA treatment and under abiotic stresses.