Study on enhancement of wide-range stress tolerance by rhizosphere control on moleculartolerance by rhizosphere control on molecular base.

点击翻译按钮获取中文摘要

Acid and alkaline soils occupy over half of arable land in the world. Plant growth is inhibited in these soils because of the insolubilization of nutrients and toxicity of inorganic compounds such as A1 and heavy metals. Recently, it is indicated that the plant roots have some strategy to improve the rhizosphere environment (about several μm from root surface). We have studied to increase the capacity of function for rhizosphere regulation. The results of this study are summarized as follows;1) A cDNA for LASAP2 encoding acid phosphatase secreted from white lupin roots was transformed into tobacco plants. Genomic DNA containing promoter region was transformed into rice plants. These plants were able to secrete the acid phosphatase which had mostly same properties with native mature protein of white lupin roots.2) To introduce the PEPC (phosphoenolpyruvate carboxylase) gene into rice plants, some gene constructs for transformation using Agrobacterium were designed. For the efficient expression of PEPC, a transgenic rice line containing PEPC gene under regulation of actin promoter was selected. Novel gene for PEPC was isolated from rice plant, and the function was analyzed. The novel PEPC was C3 type and specifically induced in leaves. The identity was about 80% with root type PEPC. The A1 and low P tolerances were improved in PEPC transgenic rice line because overexpression of mRNA and protein for PEPC causes the increase of oxalate secretion from roots.3) Effect of root exudates of P-deficient onion on hyphal growth of arbuscular mycorrhizal fungi were studied. A1 fraction (Rf:0.47) was isolated by TLC from ethyl acetate fraction of onion root exudates. Spores of Gigaspora margarita were incubated in this fraction and deionized water (control) for 7 days. Length of external hyphae and number of 2nd or higher order branches were higher in A1 fraction than in control.