Introduction of the PPF1 gene into rice (Oryza sativa L.) results in delayed leaf senescence

PPF1, a post-floral-specific gene expressed in short-day-grown G ₂ pea, has been introduced into japonica rice variety Zhonghua 9 by use of Agrobacterium-mediated transformation. A delayed leaf senescence line, designated line 269, was generated from T₂ generation plants. PCR and Southern blot analysis indicated that the foreign DNA fragment was successfully integrated into the rice genome. By classic genetic linkage analysis, the introduced PPF1 gene was also proved to be inherited as a single Mendelian factor and to be the cause of the delayed leaf senescence-delaying phenotype. RT-PCR results also suggested that PPF1 expressed stably in this transgenic line. As a result, apparent inhibition of the process of leaf senescence was observed. Chlorophyll content, net photosynthetic rate, and stoma conductance were also significantly or very significant improved in line 269. Significantly improvements in panicle weight, and 1,000-grain weight, yield per plant, and seed-setting rate were also observed for this transgenic line. We thus believe that expression of PPF1 gene in rice suppressed leaf senescence and hence increased productivity, possibly by controlling chloroplast development.