methampicillin and gibberellic-acid

Fruit ripening is a unique plant developmental process with direct implications for our food supply, nutrition, and health. In contrast to climacteric fruit, where ethylene is pivotal, the hormonal control of ripening in nonclimacteric fruit, such as grape (Vitis vinifera), is poorly understood. Brassinosteroids (BRs) are steroidal hormones, essential for normal plant growth and development but not previously implicated in the ripening of nonclimacteric fruit. Here we show that increases in endogenous BR levels, but not indole-3-acetic acid (IAA) or GA levels, are associated with ripening in grapes. Putative grape homologs of genes encoding BR biosynthesis enzymes (BRASSINOSTEROID-6-OXIDASE and DWARF1) and the BR receptor (BRASSINOSTEROID INSENSITIVE 1) were isolated, and the function of the grape BRASSINOSTEROID-6-OXIDASE gene was confirmed by transgenic complementation of the tomato (Lycopersicon esculentum) extreme dwarf (dx/dx) mutant. Expression analysis of these genes during berry development revealed transcript accumulation patterns that were consistent with a dramatic increase in endogenous BR levels observed at the onset of fruit ripening. Furthermore, we show that application of BRs to grape berries significantly promoted ripening, while brassinazole, an inhibitor of BR biosynthesis, significantly delayed fruit ripening. These results provide evidence that changes in endogenous BR levels influence this key developmental process. This may provide a significant insight into the mechanism controlling ripening in grapes, which has direct implications for the logistics of grape production and down-stream processing.

Topics: Cloning, Molecular; Gene Expression Regulation, Plant; Gibberellins; Indoleacetic Acids; Molecular Sequence Data; Phylogeny; Plant Growth Regulators; Plant Proteins; Plants, Genetically Modified; Signal Transduction; Solanum lycopersicum; Steroids; Triazoles; Vitis

Solenogyne mikadoi is a subtropical rheophyte endemic to the Ryukyu Archipelago that develops rosette leaves 2-3 cm in diameter. In contrast, the other three species of this genus all occur in temperate grasslands of Australia and develop rosette leaves about 10 cm in diameter. To examine the involvement of the plant hormones gibberellin and brassinosteroid in the adaptive dwarfism of S. mikadoi, we compared the effects of GA(3) and brassinolide, and their biosynthesis inhibitors on the morphology of the first leaves of S. mikadoi and its temperate relative S. bellioides. In S. mikadoi, one-directional (lengthwise) leaf elongation was strongly facilitated by the application of GA(3) and suppressed by a gibberellin-biosynthetic inhibitor, uniconazole-P, while leaf width (transverse) expansion was insensitive to and was never facilitated by any of the compounds used. Conversely, in S. bellioides, brassinolide facilitated both the elongation and expansion of leaves, while a brassinosteroid-specific biosynthesis inhibitor, brassinazole220, suppressed both. One-directional leaf elongation caused by the reduced sensitivity to brassinolide in S. mikadoi and brassinolide-dependent two-dimensional leaf expansion in S. bellioides both appear to be adaptations to their respective habitats: S. mikadoi has narrow leaves resistant to flowing water, whereas S. bellioides has broad leaves capable of harnessing sufficient light and water in temperate grasslands.

Topics: Asteraceae; Ecosystem; Gibberellins; Plant Growth Regulators; Plant Leaves; Steroids; Time Factors; Triazoles

Brassinazole is the only known specific brassinosteroid (BR)-biosynthesis inhibitor, and it has been shown to be useful for elucidating the function of BRs. In the course of a structure-activity relationship study of brassinazole, we found a more specific BR-biosynthesis inhibitor, Brz2001. This new inhibitor induced similar morphological changes to those seen in brassinazole-treated plants, including Arabidopsis thaliana (L.) Heynh., Nicotiana tabacum L., and Lepidium sativum L. These changes included dwarfism with altered leaf morphology, including downward curling and dark-green color, and the changes were reversed by brassinolide. Although the structure of Brz2001 is similar to that of uniconazole, a gibberellin-biosynthesis inhibitor, Brz2001-treated plants showed almost no recovery with the addition of gibberellic acid (GA3). Comparison of the responses of both brassinazole- and Brz2001-treated cress to brassinolide and GA3 suggested that Brz2001 is a more specific BR-biosynthesis inhibitor than brassinazole. Unlike the results just described, Brz2001-treated rice did not show any morphological changes. This suggests that the roles of BRs in rice may be different from those in the dicotyledonous plants examined in this study. Brz2001 can be used to clarify the function of BRs in dicots as a complement to BR-deficient mutants, and to elucidate the different roles of BRs in monocots and dicots.

Topics: Arabidopsis; Brassinosteroids; Cholestanols; Cotyledon; Gibberellins; Hypocotyl; Nicotiana; Oryza; Phytosterols; Plant Development; Plant Growth Regulators; Plants; Steroids, Heterocyclic; Structure-Activity Relationship; Triazoles