TCD5 Enhances the Photosynthesis Capacity, Increases the Panicle Number and the Yield in Rice

Improvement of photosynthetic efficiency is a major approach to increase crop yield potential. Previously, we cloned a gene encoding the chloroplast-located putative monooxygenase TCD5, which is essential in plastid development under low temperature in rice (Oryza sativa L.). In this study, the effects of TCD5 on the photosynthesis and the yields were investigated in rice. Two sets of genetic materials with three levels of TCD5 expression, including tcd5 mutant or TCD5 RNAi transgenic lines and TCD5 over-expression transgenic lines in Jiahua1 and Nipponbare backgrounds, were used in the field trails of multi-locations and multi-years. TCD5 positively affected the panicle number and the yield at dosage. Compared with the wild-types, the panicle numbers were 12.4%-14.6% less in tcd5 mutant and 8.3%-38.6% less in TCD5 RNAi lines, but 26.2%-61.8% more in TCD5 over-expression lines. The grain yields per plant were 9.1%-18.4% less in tcd5 mutant and 14.3%-56.7% less in TCD5 RNAi lines, but 6.9%-56.5% more in TCD5 over-expression lines. The measurements of net photosynthetic rate indicated that mutation or knock down of TCD5 decreased the net photosynthetic rate by 10.4% and 15.6%, respectively, while increasing it by 8.9% and 8.7% in the TCD5 over-expression lines in Jiahua1 and Nipponbare backgrounds, respectively. Accordingly, the measurements of chlorophyll fluorescence parameters showed that the electron transport rate and quantum yield decreased in tcd5 mutant or TCD5 RNAi lines but increased in TCD5 over expression lines, both in Jiahua1 and Nipponbare backgrounds. IP-MS screening revealed that TCD5 interacts with 29 chloroplast proteins involved in chlorophyll synthesis, photo-reactions of the photosynthesis, carbon assimilation and metabolism, energy metabolism, redox balance, protein synthesis and transportation. Two TCD5 interacted proteins, D1 and FBA were effective targets for improving photosynthesis. These results suggest a potentially new strategy for increasing rice yield by enhancing photosynthesis.