Expression of ripening-related genes in prickly pear (Opuntia sp.) fruits.

To throw light on the expression of ripening-related genes in prickly pear (Opuntia sp.) fruits and on the possible role of the gaseous hormone ethylene in nonclimacteric fruit ripening, cDNA fragments that showed high homologies with 1-aminocyclopropane-1-carboxylate (ACC) synthase and ACC oxidase cDNAs from other plants were cloned and partially characterized. Thus, the corresponding genes were accordingly named opaccs-1 and opacco-1, after Opuntia ACC synthase-1 and Opuntia ACC oxidase-1, respectively. Southern analysis suggests the presence of at least one copy of both genes, as well as other related homologous sequences in the Opuntia genome. Northern analysis of the opaccs-1 gene shows an enhanced expression in ripening fruit tissues, whereas opacco-1 expression is highly induced in ripe tissues with respect to the green fruits and mature cladodes. These results are in agreement with an active metabolic role of ethylene during nonclimacteric prickly pear fruit ripening. This is the first report on the analysis at the molecular level of ripening-related genes of the Opuntia genus.

Detection of genetic variation in Ustilago maydis strains by probes derived from telomeric sequences.

Genetic variation using probes derived from telomeric sequences was analysed among several Ustilago maydis strains in an attempt to identify discriminative fingerprint patterns. Three groups of wild isolates from different geographical areas and one group of standard laboratory strains were examined. Analysis of the endmost restriction fragments (EFs) and of the endmost-associated restriction fragments (EAFs) of the chromosomes revealed group differences. Most of the EFs in two groups of strains showed a similar length whereas in the other two groups they were distributed in classes of different lengths. Furthermore, analysis of the EAFs permitted possible fingerprint patterns to be predicted for each group of strains based on the occurrence of amplified bands as well as the presence or absence of distinct bands which were shown to be present in terminal as well as in interstitial sites of the chromosome. The approach evaluated in this work yielded highly polymorphic fingerprint patterns and could be used to distinguish groups of fungal isolates; this approach may also be effective for other fungal systems.

Huitlacoche (Ustilago maydis) as a food source--biology, composition, and production.

Huitlacoche is the ethnic name applied to the young fruiting bodies (galls) of the fungus Ustilago maydis, which causes common smut of maize (Zea mays L). Biologists and agronomists have historically used U. maydis as a model to study a wide array of genetic, physiological, ecological, and phytopathological phenomena. In Mexico and other Latin American countries, huitlacoche has been used traditionally as human food, being highly regarded as an interesting dish or condiment. The food potential of huitlacoche is described here in terms of its chemical composition, which includes carbohydrates, proteins, fats, vitamins, and minerals. In addition, essential amino acids (especially lysine) and fatty acids (linoleate) are present in huitlacoche in considerable levels, adding to its nutritional attributes. The feasibility of growing U. maydis in submerged agitated culture has yielded a variety of fermentation products, including essential amino acids, proteins, vitamins, and flavorings, among others. Recent interest in developing huitlacoche as a cash crop has come from increasing acceptance by the North American public, who prize it as a new delicacy. However, research efforts are still needed to determine the biological factors involved in the establishment of U. maydis as a pathogen on the maize plant. This review deals with the role of huitlacoche as a food source, implicating the biological components that will determine the development of technologies for large scale production.