Expression And Function Analysis Of SHB1 Gene During Arabidopsis Seed Development

Seeds are the most important resources of human food, and some seeds are significant industrial materials, which has a close relationship with human life and production. Therefore, improving the seed yield by various genetic and molecular methods has an important role. Seed size is one of the main factors to affect seed yield. Using Arabidopsis as the model plant, study on the molecular mechanism and finding new genes to control seed size have important theoretical values and can be used to practice, which plays a crucial role in the improvement of seed yield. Seeds of a gain-of-function mutant shb1-D, are larger than that of Wassilewskija (Ws) wild type. While seeds of a loss-of-function mutant shb1-L, are slightly smaller than Colombia (Col) wild type. Through the study of the two kinds of mutants in the control of seed size, following results and conclusions were obtained:1. Both embryo cell size and cell number are increased in shb1-D mutantAnalysis of cell size and cell number in mature embryos indicated that both cell size and cell number were increased in shb1-D mutant embryos compared with Ws wild type, and both of them were slightly reduced in shb1-L mutant embryos.2. Seed development stages are delayed in shb1-D mutantComparative analysis between shb1-D mutant and Ws wild type seeds at the same time after pollination showed that the embryo development stage in shb1-D mutant is later than that of Ws wild type; while the progress of embryo development is similar between shb1-L mutant and Col wild type.3. Expression of SHB1 in different organs To understand the expression pattern of SHB1 gene, we examined the expression of beta-glucuronidase (GUS) gene driven by the SHB1 promoter. The GUS signal was detected in flowers, mature pollen grains, pollen tubes, seedlings and pre-pollinated ovules. This data indicates that SHB1 is expressed in different organs. In-situ hybridization experiment revealed that SHB1 was expressed in embryos and endosperm at different development stages. These results suggest that SHB1 is involved in the control of seed development.4. Delayed endosperm cellularization of shb1-D mutantCytological analysis showed that endosperm of Ws wild type has been cellularized, while endosperm of shb1-D mutant has not been cellularized at 5 days after pollination, and at the early-heart embryo stage. This result reveals that delayed endosperm cellularization may cause producing larger seeds.The results demonstrate that SHB1 gene is involved in the control of Arabidopsis seed size. SHB1gene is overexpressed in shb1-D mutant and results in larger seeds. Our data provided important information to further study the mechanism of seed size determination.