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1.
New Phytol ; 224(3): 1133-1141, 2019 11.
Article in English | MEDLINE | ID: mdl-31032938

ABSTRACT

Water-mediated fertilization is ubiquitous in early land plants. This ancestral mode of fertilization has, however, generally been considered to have been lost during the evolutionary history of terrestrial flowering plants. We investigated reproductive mechanisms in the subtropical ginger Cautleya gracilis (Zingiberaceae), which has two pollen conditions - granular and filiform masses - depending on external conditions. We tested whether rain transformed granular pollen into filiform masses and whether this then promoted pollen-tube growth and fertilization of ovules. Using experimental manipulations in the field we investigated the contribution of water-mediated fertilization to seed production. Rain caused granular pollen to form filiform masses of germinating pollen tubes, which transported sperm to ovules, resulting in fertilization and seed set. Flowers exposed to rain produced significantly more seeds than those protected from the rain, which retained granular pollen. Insect pollination made only a limited contribution to seed set because rainy conditions limited pollinator service. Our results reveal a previously undescribed fertilization mechanism in flowering plants involving water-mediated fertilization stimulated by rain. Water-mediated fertilization is likely to be adaptive in the subtropical monsoon environments in which C. gracilis occurs by ensuring reproductive assurance when persistent rain prevents insect-mediated pollination.


Subject(s)
Fertilization/physiology , Water , Zingiberaceae/physiology , Animals , Bees/physiology , Flowers/physiology , Germination/physiology , Linear Models , Pollination , Rain , Seeds/physiology , Self-Fertilization
2.
Sci Rep ; 8(1): 3634, 2018 02 26.
Article in English | MEDLINE | ID: mdl-29483537

ABSTRACT

About 20% of angiosperms employ self-fertilization as their main mating strategy. In this study, we aimed to examine how the selfing timing correlated with floral traits in three Gentianopsis species in which autonomous selfing is achieved through filament elongation. Although the three Gentianopsis species exhibit no significant variation in their capacity for autonomous selfing, flowers of G. grandis last longer, are larger and have a higher corolla biomass, P/O ratios and male biomass allocation than those of G. paludosa, and especially those of G. contorta. Autonomous selfing occurs in the early floral life of G. paludosa and G. contorta and in the later floral life of G. grandis. Seed production mainly results from autonomous selfing in G. paludosa and G. contorta; however, G. grandis could be more described as having a mixed mating system. We suggest that autonomous selfing in later floral life increases the chance of cross-pollination prior to this, while autonomous selfing in early floral life offers a selective advantage to plants by reducing the resource investment in traits that may increase pollinator attraction and visitation.


Subject(s)
Flowers/physiology , Gentianaceae/physiology , Pollination/physiology , Reproduction/physiology , Seeds/physiology , Self-Fertilization/physiology
3.
Antioxid Redox Signal ; 5(5): 677-88, 2003 Oct.
Article in English | MEDLINE | ID: mdl-14580325

ABSTRACT

Manganese superoxide dismutase (MnSOD) is an antioxidant enzyme with tumor suppressor activity; however, the molecular mechanisms of MnSOD antitumor effects remain unclear. We hypothesized that MnSOD activity in cancer cells might cause downstream changes in the expression of other tumor suppressor genes. To determine whether maspin, a tumor suppressor gene that inhibits breast cancer cell invasion and metastasis, might be a target of MnSOD, we forced MnSOD expression in several human breast and prostate cancer cell lines by adenovirus-mediated gene transfer and measured maspin mRNA expression. Forced expression of MnSOD caused maspin mRNA to accumulate in a dose-dependent manner in both human breast and prostate cancer cells. Normal p53 was not necessary to mediate the effect of MnSOD because MnSOD up-regulated maspin in cells that harbor wild-type p53 and in cells that harbor mutant p53. Moreover, the effects of MnSOD on maspin were not due to demethylation of the maspin promoter. Analyses of maspin promoter activity, transcriptional run-on, and mRNA stability showed that maspin mRNA stability was the major mechanism for maspin up-regulation by MnSOD. Our findings identify a mechanism underlying MnSOD antitumor effects and provide evidence to support MnSOD as a genetic therapy in the treatment of human breast and prostate cancers.


Subject(s)
Gene Expression Regulation, Neoplastic , Proteins/genetics , Serpins/genetics , Superoxide Dismutase/physiology , Adenoviridae/genetics , Base Sequence , Blotting, Northern , Blotting, Western , Breast Neoplasms/genetics , Breast Neoplasms/pathology , Cell Line , Cell Line, Tumor , DNA Methylation , Dactinomycin/pharmacology , Female , Genes, Tumor Suppressor , Genetic Vectors/genetics , Humans , Kinetics , Male , Molecular Sequence Data , Mutation/genetics , Promoter Regions, Genetic/genetics , Prostatic Neoplasms/genetics , Prostatic Neoplasms/pathology , Proteins/metabolism , RNA Stability/drug effects , RNA, Messenger/drug effects , RNA, Messenger/genetics , RNA, Messenger/metabolism , Serpins/metabolism , Superoxide Dismutase/genetics , Superoxide Dismutase/metabolism , Transcription, Genetic/genetics , Transfection , Tumor Suppressor Protein p53/genetics , Tumor Suppressor Protein p53/metabolism , Up-Regulation
4.
Mol Carcinog ; 33(4): 206-18, 2002 Apr.
Article in English | MEDLINE | ID: mdl-11933074

ABSTRACT

The ras proto-oncogene is frequently mutated in human tumors and functions to constitutively stimulate signal transduction cascades, resulting in unchecked proliferation and malignant transformation. In certain cells, superoxide functions as a signal-transduction messenger, mediating the downstream effects of ras and rac. We demonstrated previously that v-Ha-ras-transfected rat kidney epithelial cells (RECs) overproduced superoxide anion and that this superoxide production was mediated by ras. In the present study, we further demonstrated that v-Ha-ras overexpression transformed immortal nonmalignant RECs into malignant cancer cells; v-Ha-ras-transfected cells formed clones in soft agar, had high plating efficiency, and formed tumors in nude mice. Our data suggest that superoxide radical plays a role in ras-induced transformation; modulation of intracellular superoxide level by overexpression of manganese-containing superoxide dismutase or copper- and zinc-containing superoxide dismutase inhibited ras-induced transformation, as evidenced by in vitro studies of plating efficiency and by in vivo studies of tumor formation in nude mice. Overexpression of catalase (CAT) alone was found to have little effect on tumor cell growth, but overexpression of glutathione peroxidase 1 (GPx1) completely suppressed tumor cell growth in nude mice. This finding suggests that peroxides removed by GPx1, but not by CAT, are also involved in ras-induced transformation.


Subject(s)
Genes, ras , Mitogens/physiology , Reactive Oxygen Species/metabolism , Signal Transduction/physiology , Superoxides/metabolism , Animals , Catalase/genetics , Catalase/metabolism , Cell Division , Cell Line , Colony-Forming Units Assay , Glutathione Transferase/genetics , Glutathione Transferase/metabolism , Kidney , NF-kappa B/metabolism , Oncogene Protein p21(ras)/genetics , Oncogene Protein p21(ras)/metabolism , Proto-Oncogene Mas , Rats , Recombinant Proteins/metabolism , Superoxide Dismutase/genetics , Superoxide Dismutase/metabolism , Transcription Factor AP-1/metabolism , Transfection , Urothelium
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