Isolation and characterization of ribosome-inactivating proteins from Cucurbitaceae.[Pubmed: 17372945]

Due to their RNA-N-glycosidase activity, ribosome-inactivating proteins (RIPs) are attractive candidates as antitumor and antiviral agents in biomedical and agricultural research. We have isolated and characterized two such proteins, foetidissimin II and texanin, from two Cucurbitaceae species. Foetidissimin II, obtained from the roots of Cucurbita foetidissima, was identified as a type-2 RIP, with a molecular weight of 61 kDa, as estimated by gel electrophoresis. It is composed of two chains, a 29-kDa chain A, and a 32-kDa chain B. Texanin, isolated from the fruits of Cucurbita texana, is a type-I RIP, with a single chain of molecular weight 29.7 kDa, as estimated by MALDI-TOF-MS. Both proteins exhibit RNA-N-glycosidase activity, with aniline playing a critical role in rRNA cleavage. The IC50 value of foetidissimin II, determined by cell-free protein-synthesis inhibition, was 0.251 muM. In an in vitro cytotoxicity assay, foetidissimin II exhibited IC50 values of ca. 70 nM to both adenocarcinoma and erythroleukemia cells. Texanin exhibited a weaker anticancer activity against erythroleukemia cells, with an IC50 value of 95 microM, but no activity against adenocarcinoma cells. The N-terminal sequences of both proteins were compared with those of reported RIPs.

Pollen competition in a natural population of Cucurbita foetidissima (Cucurbitaceae).[Pubmed: 10766724]

The pollen competition hypothesis predicts that when the number of pollen grains deposited onto stigmas exceeds the number of ovules, selection can operate in the time frame between deposition and fertilization. Moreover, because of the overlap in gene expression between the two phases of the life cycle, selection on microgametophytes may alter the resulting sporophytic generation. The extent to which pollen competition occurs in nature has been unclear, because tests of the predictions of the pollen competition hypothesis have used cultivars and/or artificial growth conditions and hand-pollination techniques. In this study we used a wild species, Cucurbita foetidissima, in its natural habitat (southern New Mexico) to determine the amount and timing of the arrival of pollen onto stigmas, the relationship between pollen deposition and seed number, and the effects of the intensity of pollen competition on progeny vigor. We found that ∼900 pollen grains are necessary for full seed set and that a single visit by a pollinator results in the deposition of 653.0 ± 101.8 pollen grains. About 29% of the flowers receiving a single pollinator visit had 900 or more pollen grains on its stigma. Moreover, within 2 h of anthesis, >4000 pollen grains were deposited onto a typical stigma, indicating that multiple pollinator visits must have occurred. Fruits produced by multiple visits had greater seed numbers (206 vs. 147) than fruits produced by a single visit. Finally, the progeny produced by multiple pollinator visits were more vigorous than those produced by single visits with respect to five measures of vegetative growth (MANCOVA, Wilks' lambda = 0.96, F(6,370) = 2.54, P < 0.02. These data demonstrate that conditions for pollen competition exist in nature and support the prediction that pollen competition enhances offspring vigor.

A new major triterpene saponin from the roots of Cucurbita foetidissima.[Pubmed: 10650092]

Foetidissimoside B (1), a novel triterpene saponin, was isolated from the roots of Cucurbita foetidissima. Based on spectroscopic data, especially direct and long-range heteronuclear 2D NMR analysis and on chemical transformations, the structure of 1 was elucidated as 3-O-beta-D-glucuronopyranosyl-echinocystic acid 28-O-beta-D-glucopyranosyl-(1-->3)-beta-D-xylopyranosyl(1-->3)-[beta- D-xylopyranosyl (1-->4)]-alpha-L-rhamnopyranosyl-(1-->2)-alpha-L-arabinopyranoside . Compound 1 did not show any ability to potentiate in vitro cisplatin cytotoxicity in a human colon cancer cell line.

SEX RATIO, SEED PRODUCTION, BIOMASS ALLOCATION, AND THE COST OF MALE FUNCTION IN CUCURBITA FOETIDISSIMA HBK (CUCURBITACEAE).[Pubmed: 28564233]

In the gynodioecious plant Cucurbita foetidissima (Cucurbitaceae), females were common in all eight populations examined and made up 32% of adult plants. Females produced 1.5 (SE = 0.2) times as many seeds as did hermaphrodites. The observed difference in seed production alone is not great enough to explain the maintenance of females, especially at their current frequency. Females and hermaphrodites did not differ in number of nodes per stem, stems per plant, internode length, or size of leaves. Females produced more female biomass (fresh or dry weight) than hermaphrodites, but total investment in sexual biomass did not differ. Thus, the biomass of male flowers produced by hermaphrodites was about equal to the extra female biomass produced by females. The results support the existence of a trade-off between male and female reproduction.

Feasibility of enzymatic hydrolysis and alcoholic fermentation of starch contained in buffalo gourd (Cucurbita foetidissima) roots.[Pubmed: 18576470]

The suitability of using annually grown, carrot-sized buffalo gourd (Cucurbita foetidissima) roots as a feedstock for alcoholic fermentation was explored. Roots grown in 1982 and 1983 were slurried, dextrinized and saccharified using Takathermtrade mark and Diazymetrade mark (commercial enzymes manufactured by Miles Laboratories), and fermented by the action of Saccharomyces cerevisiae. These processes were monitored in detail and results were compared with those displayed by controls formulated using potato tubers. The preparation of gourd root slurries with suitable viscosity characteristics for enzymatic digestion required the addition of water (at least 50% by weight) which reduced the proportion of fermentable sugars in the resulting saccharified suspensions. The resulting slurries were well-suited to enzymatic conversion of starch to sugar. Estimates of enzymatic efficiency in gourd root suspensions did not suggest the presence of naturally occurring amylase or glucosidase inhibitors in these plant materials. Saccharified gourd root mashes supported yeast growth well and produced ethanol yields at 82.2-86.5% of the theoretically maximum efficiency.