Effects On Salt Tolerance And Photosynthetic Characteristics By Overexpression Of Chloroplast Dehydrogenase Genes ZmNdhl2 And OsNdhl In Rice

Salt stress is an important abiotic stress that restricts crop growth.Cyclic electron transport around photosystem I（CET-PSI）evolved in higher plants is one of the ways to provide light protection mechanism to deal with natural environmental stress.Chloroplast dehydrogenase complex（NDH）participates in the cyclic electron transfer around PSI,provides additional ATP for CO2 assimilation in adverse environment,and then improves the adaptability of plants to adverse environment.The expression of NDH in C4 plants is higher than that in C3 plants,which is the main factor that causes the CET of C4 plants to be stronger than that of C3 plants.In the previous study,the ZmNdhl1 gene of C4 plant maize was screened by bioinformatics technology,and it was found that the overexpression of ZmNdhll gene in C3 plant rice can effectively improve the salt tolerance and photosynthetic characteristics of rice.In this study,the homologous gene ZmNdhl2 of ZmNdhll in maize and OsNdhl in rice were overexpressed in rice,the effects of these two genes on salt tolerance and photosynthetic characteristics of rice were studied,and the effect differences among ZmNdhl1,ZmNdhl2and OsNdhl were compared in order to provide a basis for improving stress resistance of rice.The main results are as follows:1.Analysis of salt tolerance of ndhl gene overexpression rice.Five positive lines were identified in Maize ZmNdhl2 overexpression rice and six positive lines were identified in rice OsNdhl overexpression rice.The results showed that under salt stress,the plant height,dry weight and relative water content of ZmNdhl2 and OsNdhl overexpression rice lines were significantly higher than those of the negative control;The content of malondialdehyde was significantly lower than that of the negative control.Comparing the characters of ZmNdhl1,ZmNdhl2 and OsNdhl overexpressed rice,it was found that there was no significant difference among the three transgenic materials.The above results showed that overexpression of ZmNdhl2 and OsNdhl genes in rice could enhance salt tolerance and play similar functions.2.Analysis of photosynthetic electron transport activity of ndhl gene overexpression rice under salt stress.Under salt treatment,the results showed that the circulating electron transfer activity and rate of transgenic materials were higher than those of negative control materials,and there was no significant difference among the three transgenic materials;Compared with negative materials,transgenic materials had less deformation of instantaneous chlorophyll fluorescence curve and less decrease of J,I and P points;The elevation of modulated 820 nm light reflection curve is small,and the maximum rising slope and maximum falling slope have no significant change;The amplitude of delayed chlorophyll fluorescence curve decreased less,and the decrease of I1 point was less.The above results showed that the overexpression of ZmNdhl2,OsNdhl genes in rice increased the activity of CET,slowed down the damage of cyclic electron transport between PSⅡ and PSⅠ,alleviated the oxidative damage of PC and P700 under salt stress,and reduced the damage of electron transport on the receptor side of PSI,so as to improve the salt tolerance of rice,and there was no significant difference among different genes.3.Analysis of agronomic characters and Photosynthesis of ndhl gene overexpression rice in field.In the field growth environment,there was no significant difference between transgenic materials and negative control materials in plant height,panicle length,number of effective tillers and yield per plant;Under the condition of leaf senescence,the net photosynthetic rate and cyclic electron transfer activity of transgenic materials were significantly higher than those of negative materials.The results showed that there was no significant difference in plant height and yield correlation between transgenic rice and control materials;Under the condition of rice leaf senescence,there was no significant difference in the expression of ZmNdhl1,ZmNdhl2 and OsNdhl genes.