Salt Tolerance And Photosynthetic Characteristics Of Overexpressed Rice Lines Containing The Maize ZmNdhl1 Gene

Cyclic electron transport around PSI(CET-PSI)mediated by NAD(P)H dehydrogenase complex is a very important protective mechanism for plants to adapt to a variety of natural environmental stresses in higher plant.Previous studies showed that the different expression of NAD(P)H dehydrogenase on the chloroplast thylakoid membrane between C4 plant and C3 plant was the main factor that caused the different strength of CET in these two species.In the previous study,we identified 27 NDH genes in maize genome,and found that two gene families Ndhl and PnsB2 experienced positive selection by comparion the NDH genes in C4 species with those in C4 species.Furthermore,the gene from these two families have two copies in C4 species maize or sorghum and one copy in C3 species rice.Real-time quantitative analysis of two gene families Ndhl and PnsB2 in maize showed that ZmNdhLl gene had the highest expression level.It is hypothesized that ZmNdhLl gene could be one of the reasons for the higher strength of NDH complex-mediated CET in C4 species than in C3 species.To test this hypothesis,trangenic rice lines with overexpressed ZmNdhLl gene were constructed.Salt tolerance and photosynthetic performance of these transgenic lines were investigated.In addition,RNA-seq technique was used for transcriptome analysis for transgenic rice lines under control and salt treatment conditions.The main results are as follows:1.Obtainment of rice transgenic overexpressing lines and analysis of salt tolerance.The positive transgenic rice lines with overexpressed ZmNdhLl gene were screened.RT-PCR results showed that the transgenic rice lines of OX-1 and OX-2 were positive.The results of qRT-PCR and Western-Blotting indicated that ZmNdhL1 gene in OX-1 and OX-2 lines were overexpressed.In addition,transgenic lines OX-1 and OX-2 were more salt-tolerant,and showed more dry matter accumulation than control lines with introduced empty Vector at the seedling growth stage.2.Photosynthetic characteristics of transgenic rice.The effect of ZmNdhll gene on the photosynthetic electron transport chain was identified.It was found that the ZmNdhll gene increased the activity of CET in rice under normal condition,induced the activity of CEF under salt stress,and reduced the damage caused by salt stress on the photosynthetic electron transport chain including the PSII donor side,electron transfer between PSII and PSI,and the PSI acceptor side.3.Transcriptome analysis of transgenic rice.The results showed that there were 4 differentially expressed genes in the OX-1 and OX-1 and Vector before and after salt treatment.26 differentially expressed genes are unique to OX-1 and OX-2,of which 4 genes have unknown function,of which 7 are up-regulated DEGs,15 are down-regulated DEGs,and most of up-regulated DEGs respond to stresses.