Mechanism Of OsRNase Z2 Regulating The Transformation Of Linear And Cyclic Electron Flow In Rice

In photosynthesis,light energy is converted into a chemical energy of ATP form in the chloroplast thylakoid membrane,and NADP+ is reduced to NADPH,which forms two forms of electron flow in the chloroplast.The electrons produced by the photolysis of water are transferred through the photosystem I(PS I)and the photosystem II(PS II),transferred to NADP+,resulting in the accumulation of NADPH and simultaneously synthesizing ATP,which is called linear electron transfer(LET).The circulatory electron transfer around PS I is also indispensable for the efficient operation of photosynthesis.Electrons are circulated between NAD(P)H or iron oxygen reducing protein(Fd)to plastid quinone(PQ),and PS I circulates only to produce ?pH without accumulating NADPH.Among them,the chloroplast NDH complex mediated PSI cyclic electron transport has attracted more attention.At present,the main function of cyclic electron transfer is to increase the supply of ATP to balance the ATP/NADPH ratio.In addition,the cyclic electron transfer is an indispensable factor to provide sufficient electron power for the luminescent protection mechanism.The chloroplast NDH complex is a ferric reductin quinone reductase(FQR),which is insensitive to mycin A.It combines Fd with NdhS subunit to bind to the NDH complex.The chloroplast NDH complex of higher plants is composed of more than 30 subunits,which combine with PS I to form a super complex,which mediates the cyclic electron transport around PSI-NDH.This study found that some of the interfered plants of RNase Z2 in rice appeared to be yellow or even albino.Further fluorescence quantitative detection showed that the severity of the phenotype of the interfered plant was negatively correlated with the expression of RNase Z2.The transcriptional analysis of RNase Z2 interfering plants showed that the expression of NDH complex subunit genes encoded by the chloroplast genes was significantly up-regulated compared with the wild type plants interfering plants.The diurnal variation analysis of these genes also showed a negative correlation with the expression of RNase Z2.The vitro experiments of RNase Z2 showed that it could specifically degrade ndhD and ndhF mRNA.The accumulation of PSI-NDH supercomplex and NDH complex in RNase Z2 RNA interference plants was increased by the blue negative electrophoresis and Western Blot of thylakoid membrane protein.Furthermore,chlorophyll fluorescence assay showed that the NDH complex activity and P700 redox rate of the interfered plants were higher than those of wild type plants.Chlorophyll fluorescence detection of ndhD and ndhF overexpressing plants also revealed similar results of RNase Z2 RNA interference.