Research Of Brassinosteroid’s Roles In Peanut Pod Development

Brassinolide (BR) is a plant hormone, which widely presents in pollen, seed, stem and leaf and other organs of plant. It plays a significant role in the promotion of crop growth and yield. Peanuts are major oil crops in China and more than 50% of the peanut are used for oil production. Peanut seeds are rich in nutrition, and are important raw material in food industry. For a long time, how to improve the quality and yield of peanuts are major concerns for peanut breeders. In this study, we investigated the roles of BR in peanut pod development, and we hope that the results could help to elucidate the mechanisms underlying the geocarpic development of peanut pod, to provide informations for quality improvement and yield increasement in peanuts.To study exogenous BR and its inhibitor on pod development, the current study compared the growth and development of pods that are treated with different concentration of BR and BR inhibitor using gynophores of field-planted LH14. Specifically, gynophores were treated with three concentrations of brassinolide (0.01 mg/L,0.1 mg/L,1.0 mg/L) and brassinosteroid hormone inhibitor, respectively. The results showed that BR had a negative effect on ovary enlargement. While, a positive effect on ovary enlargment was observed for BR inhibitor.Moreover, the endogenous BR content of different tissues and organs of peanut were examined to understand the changing pattern of this hormone during peanut growth and development. It turned out that the BR content in peg decreased after the pegs were burried into soil to compare with the aerial grown ones. When the ovary starts to expand, the BR level keeps unchanged. Besides, we examined the BR content in bleeding sap of different organizations, it turned out that BR content in bleeding sap of stem tip and peanut pods which didn’t penetrated soil were much more than that in peanut pods which were 3-6 days after soil penetration.In order to study the role of BR signaling pathway on pod development, we cloned three genes of the BR signaling pathway:BRI1, BKI1 and BZR1. The expression of these genes in several tissues and different developmental stages of ovary was analyzed by quantitative real time PCR (qRT-PCR). Moreover, over-expression vector of BKI1 and BZR1 were constructed and successfully transformed the Arabidopsis (Columbia) in order to study the function of these genes on the plant growth and development. The transgenic Arabidopsis overexpressing the brassinosteroid receptor inhibitor kinase (BKI1) gene showed abnormal growth and development, e.g. dwarf, leaf curl, dark green color and short pod. These results indicated that brassinosteroid receptor inhibitor kinase may inhibit the plants growing; the transgenic Arabidopsis overexpressing the Brassinazole resistant 1 (BZR1) gene showed roots development better, plants grow more strong, stems’longer and embranchment more.