ABSTRACT
KEY MESSAGE: Overexpressing TaUb2 promoted stem growth and resulted in early flowering in transgenic tobacco plants. Ubiquitin are involved in the production, metabolism and proper function of gibberellin. The ubiquitin-26S proteasome system (UPS), in which ubiquitin (Ub) functions as a marker, is a post-translational regulatory system that plays a prominent role in various biological processes. To investigate the impact of different Ub levels on plant growth and development, transgenic tobacco (Nicotiana tabacum L.) plants were engineered to express an Ub gene (TaUb2) from wheat (Triticum aestivum L.) under the control of cauliflower mosaic virus 35S promoter. Transgenic tobacco plants overexpressing TaUb2 demonstrated an accelerated growth rate at early stage and an early flowering phenotype in development. The preceding expression of MADS-box genes also corresponded to the accelerated developmental phenotypes of the transgenic tobacco plants compared to that of wild-type (WT). Total gibberellin (GA) and active GA contents in transgenic tobacco plants were higher than those in WT at the corresponding developmental stages, and some GA metabolism genes were upregulated. Treatment with GA(3) conferred a similarly accelerated grown rate in WT plants to that of transgenic tobacco plants, while growth was inhibited when transgenic tobacco plants were treated with a GA biosynthesis inhibitor. Thus, the results suggest that Ub are involved in the production, metabolism and proper function of GA, which is important in the regulation of plant growth and development.
Subject(s)
Gibberellins/metabolism , Nicotiana/metabolism , Triticum/genetics , Ubiquitin/metabolism , Caulimovirus/genetics , Flowers/drug effects , Flowers/genetics , Flowers/growth & development , Flowers/metabolism , Gene Expression Regulation, Plant , Genes, Plant , Phenotype , Plant Leaves/drug effects , Plant Leaves/genetics , Plant Leaves/growth & development , Plant Leaves/metabolism , Plant Proteins/genetics , Plant Proteins/metabolism , Plant Stems/drug effects , Plant Stems/genetics , Plant Stems/growth & development , Plant Stems/metabolism , Plants, Genetically Modified/drug effects , Plants, Genetically Modified/genetics , Plants, Genetically Modified/growth & development , Plants, Genetically Modified/metabolism , Promoter Regions, Genetic , Time Factors , Nicotiana/drug effects , Nicotiana/genetics , Nicotiana/growth & development , Triazoles/pharmacology , Ubiquitin/geneticsABSTRACT
As the key regulators of cell wall extension during plant growth, expansins play an important role in regulating the development and response of plants to adverse environment. The characteristics of expansins in wheat coleoptiles and their responses to water stress were studied. Expansin proteins were extracted from wheat coleoptiles by the methods of Hepes or SDS. The activities of expansins were measured with an improved extensometer and the amount of expansins was measured by immunoblot analysis with the expansin antibody. The results showed that in coleoptiles, the extension of native cell walls depended on acidic pH, and the expansins were found to be located at cell walls by location analysis. Expansins from wheat coleoptiles could induce cell wall extension both of cucumber hypocotyls and coleoptiles, and vice versa, albeit with differences noted in extension activity. The changes in activity and abundance of expansins in wheat coleoptiles in response to water stress suggest that expansins may play a significant role in the tolerance of wheat plants to water stress.
