| Rice has been one of the world’s most important food crops, and feed about half of the population lived in the world. However, there are many biotic and abiotic stresses influencing and even causing serious damage to rice production.In recent years, there is a kind of protein named Chaperonin60(Cpn60) attracting increasing people’s attention due to its function in helping fold the key proteins involved in photosynthesis, such as Ribulose-1,5-Bisphosphate Carboxylase/oxy genase(Rubisco), NAD(P)H Dehydrogenase(NDH)complexes and Rubisco activase (RCA) etc. In rice chloroplast, Cpn60 consists 3 kinds of α and β subunits, respectively. And the study about Cpn60 protein in rice is still few. As a result, for the first time we have built and obtained two kind rice lines which are respectively over-expressed in cpn60al and cpn60α1, named cpn60β1 and cpn60β1. Then we observed the agronomic characters, measured the photosynthetic and fluorescence relevant parameters and researched their growth under salt stress with the over-expressed rice plants and their wild types. The results are as follows:Through observing the agronomic characters, we found that cpn60α1 line’s growth was close to wild type. While cpn60β1 line grew more slowly and its plant height was lower than wild type before the tillering stage. After entering the tillering stage, it grew rapidly and was ultimately significantly higher than wild type. However its tiller number was lower than the wild type. Moreover, cpn60β1 line was significantly higher in the panicle length, the total grains per spike and the weight of a thousand grains than wild type, while was just slightly lower in fruiting rate than wild type. This interesting phenomenon existing in cpn60β1 line caused the author’s attention. After analysing the photosynthetic and fluorescence characteristics, we found that two kinds of lines can improve photosynthesis responding to light. And during respond to CO2, cpn60β1 line’s carboxylation efficiency was increased significantly, indicating the increase of CO2 utilization. In addition, we also found that both lines can improve the photochemistry efficiency(Y) and electron transfer rate (ETR) of PSI and PSII in different degrees.We grew cpn60α1, cpn60β1 lines and wild type under salt stress with 150 mM NaCl concentration. The results show that both can show different degrees of salt resistance than wild type. We hypothesized that cpn60β1 can protect PSII reaction center and ensure its electron transfer through affecting NdhB and NdhH, the NDH complex protein. And it can also improve its ability to cope with stress, to maintain the growth of plants, and to improve the plant’s salt stress resistance by influencing RCA. While cpn60α1’s over-expression can enhance the expression of RCA under salt stress in rice, which on the one hand, can make more RCA participate in Rubisco’s activation to ensure photosynthesis; on the other hand can makes more RCA play its own role in protecting plants from salt stress, and then maintain the growth of plants and improve resistance of plants to salt stress.In conclusion, our research is the first time to study and proclaim that the cpn60al and cpn60β1’s over-expression can improve rice growth and photosynthesis and enhance the rice’s resistance to salt stress. We provide a new perspective on the research of rice photosynthesis and resistance to stress. |
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