Antisense Suppression Of A β-Fructosidase Gene (MAI1) In Muskmelon Affects Plant Growth And Fruit Development

The anti-MAI1 expression vector with CaMV35S promoter and Nos terminator was translated into melon inbreed line M01-3 fruits by ovary injection. PCR, Southern blot and PCR-Southern blot were performed to identify the transformation plants, the result showed that the anti-MAI1 had been transformed into the melon genomic DNA and inherited stably. The expression charactristics of AI gene were studied by Northern blot in both wide type and T₁ transgenic plants. The activities of invertase , the contents of sucrose,glucose and fructose, the vigor of growth et al were also been studied in both CK and T₁ transgenic plants. The aim of this research is to explore the AI gene expression charactristics and molecular functions in melon fruit development and sucrose metablism, and to provide the basis for the studies on AI gene and quality breeding of melon. The main results were as follows:1,The anti-MAI1 was translated into melon fruits by ovary injection. Two transgenic plants were obtained from 330 melon plants, the transformation frequency was about 0.6%, and each transgenic plant all had two anti-MAI1 copies. PCR-Southern Blot showed that the anti-MAI1 was inherited stably in T₁ generation transgenic plants.2,Total RNA was isolated form root, stem , leaf, flower and different stage fruit during fruit development in both wide type and T₁ generation transgenic plants. Northern blot was performed with DIG labeled RNA probe. The result showed that the expression of AI gene was significantly different among melon tissues and different stage of fruit development, and the mRNA expression level of AI gene decreased to great extent in transgenic plants.3,Sucrose, glucose, fructose, acid invertase and neutral invertase were extracted from different development stage fruit , and their contents and activities were studied. The result showed that the T₁ generation transgenic plants fruit had more sucrose accumulation, less glucose, fructose and lower acid invertase activity, but comparring with wide type fruit, the neutral invertase didn't have obviously change. These changes suggest that acid invertase controls sugar composition in melon fruit and the decrease of acid invertase activity is the main and indispensable prerequisite to sucrose accumulation.4,Studies on the growth curve of T₁ generation transgenic plants and fruits showed that the transgenic plants had weaker growth ability than wide type plants, and the fruit had less weight than wide type fruit. These results suggest that AI gene contributes to alterations in fruit size and plants growth ability.