Plant chlorophyll biosynthesis and chloroplast development are two complex processes that are regulated by exogenous and endogenous factors.  In this study, we identified OsDXR, a gene encoding a reductoisomerase that positively regulates chlorophyll biosynthesis and chloroplast development in rice.  OsDXR knock-out lines displayed the albino phenotype and could not complete the whole life cycle process.  OsDXR was highly expressed in rice leaves, and subcellular localization indicated that OsDXR is a chloroplast protein.  Many genes involved in chlorophyll biosynthesis and chloroplast development were differentially expressed in the OsDXR knock-out lines compared to the wild type.  Moreover, we found that the RNA editing efficiencies of ndhA-1019 and rpl2-1 were significantly reduced in the OsDXR knock-out lines.  Furthermore, OsDXR interacted with the RNA editing factor OsMORF1 in a yeast two-hybrid screen and bimolecular fluorescence complementation assay.  Finally, disruption of the plastidial 2-C-methyl-derythritol-4-phosphate pathway resulted in defects in chloroplast development and the RNA editing of chloroplast genes.

Ralstonia solanacearum causes a lethal bacterial wilt disease in many crops, leading to huge losses in crop production every year.  Understanding of plant–R. solanacearum interactions will aid to develop efficient strategies to control the disease.  As a soilborne pathogen, R. solanacearum naturally infects plants via roots.  A huge limitation in studying plant–R. solanacearum interactions is the large variation of R. solanacearum infection assay due to the variable soil conditions and uneven inoculum exposure.  Here, we developed a robust and reliable Petri-dish inoculation method which allows consistent and stable infection in young plant seedlings.  This method is easy to use, takes about only 10 days from seed germination to the completion of inoculation assay, and requires less inoculum of bacteria as well as growth chamber space.  We proved the efficacy of the seedling Petri-dish inoculation method by analyzing plant defense primed by molecular patterns, resistance of defense-related plant mutants, and virulence of R. solanacearum mutants.  Furthermore, we demonstrated that the seedling Petri-dish inoculation method can be applied to other host plants such as tobacco and has great potential for high-throughput screening of resistant plant germplasms to bacterial wilt in the future.

In China, the traditional early and late season double rice (DR) system is declining accompanied by the fast increase of two newly developed cropping systems: ratoon rice (RR) and rice–crawfish (RC).  Three methodologies: economic analysis, emergy evaluation and life cycle assessment (LCA) were employed to evaluate the economics and sustainability of this paddy cropping system change.  Economic analysis indicated that the income and profit of the RC system were far larger than those of RR and DR.  The income to costs ratio of RR and RC increased by 25.5 and 122.7% compared with that of DR, respectively.  RC had the highest emergy input thanks to increasing irrigation water, electricity, juvenile crawfish and forage input while RR showed a lower total emergy and nonrenewable emergy input, such as irrigation water, electricity, fertilizers and pesticides than DR.  The environmental loading ratios decreased by 16.7–50.4% when cropping system changed from DR to RR or from DR to RC while the emergy sustainability indexes increased by 22.6–112.9%.  The life cycle assessment indicated lower potential environmental impacts of RR and RC, whose total environmental impact indexes were 35.0–61.0% lower than that of DR.  Grain yield of RR was comparable with that of DR in spite of less financial and emergy input of RR, but RC had a much lower grain yield (a 53.6% reduction compared to DR).  These results suggested that RR is a suitable cropping system to achieve the food security, economic and environmental goals.