| Rice is one of the most important food crops,which feeds more than one half of the global population.Therefore,rice production plays an important role in food security.However,rice production is restricted by drought,water shortage,and soil salinization.Meanwhile,it is necessary to enhance the drought-resistance and salt-tolerance of the water-saving and drought-resistance rice(WDR)when promote it in some target planting areas.Therefore,the identification,research,and utilization of the drought-resistant and salt-tolerant genes to improve the drought resistance and salt tolerance is the main breeding goal of WDR.Mitochondria are the sites of plant energy metabolism and participate in plant cell differentiation,apoptosis,signal transduction and stress.Mitochondria play an important role in plant environmental adaptation and its resistance to abiotic stresses.However,more attention has been paid to nuclear genome coding genes in rice drought resistance and salt tolerance gene.Very few mitochondrial genes related to drought resistance and salt tolerance have been identified.Given the important role of mitochondrion and its encoded genes in plant environmental adaptation,it is necessary to excavate and study mitochondrial genes related to drought/salt resistance to provide new gene resources for further improving drought resistance and salt tolerance of WDR.Indica and japonica are two subspecies of cultivated rice,which have great differences in drought resistance and salt tolerance.The mitochondrial genomes of indica and japonica have great differences both of which have subspecies-specific genes.This study explored and studied potential drought and salt tolerance mitochondrial gene resources.The role of mitochondria in drought and salt tolerance of rice was evaluated in indica and japonica isonuclear alloplasmic populations from IRAT109 and Nipponbare(NIP),in order to evaluate the role of mitochondria in drought resistance and salt tolerance of rice,identify and screen mitochondrial genes related to drought and salt tolerance,so as to provide new gene resources for the improvement of drought and salt tolerance of WDR.The main findings of this study are listed below:1.There are many Open Reading frame(ORF)in the mitochondrial genome.By comparing the mitochondrial genomes of indica and japonica,15 orf specific to indica and japonica were selected.7 japonica-specific orf and 5 indica-specific orf were determined by semi-quantitative verification.We detected the expression levels of 12 indica and japonica specific orf under stress and their prokaryotic expressions.We found that 6 indica and japonica specific orf including orf124 b,orf106e,orf84 k,orf143a-1,orf108b-1,orf135 b,responded to osmotic stress and salt stress.The prokaryotic expression of these orf can affect the drought and salt tolerance of Escherichia coli.2.Through the measurement and comparison of water loss rate in detached leaves root gravity tropism and deep root ratio,it was found that there was no difference about in vitro leaf water loss rate between indica and japonica isonuclear alloplasmic populations of IRAT109 and NIP.In the aspect of root gravitytropism,the average gravity response speed of japonica isonuclear alloplasmic populations under IRAT109 background was significantly higher than that of indica,but the average gravity response speed of japonica isonuclear alloplasmic under NIP background was not significantly different.In terms of root depth ratio,there was no difference between indica and japonica isonuclear alloplasmic populations of IRAT109 and NIP.3.By evaluating and comparing the phenotypes of indica and japonica isonuclear alloplasmic populations under different concentrations of PEG6000 and Na Cl stress at seed germination,bud and seedling stages,we found that: There were no significant differences in germination rate,bud length and root length at bud stage and survival rate at three-leaf stage between indica and japonica isonuclear alloplasmic populations under stress treatment.These results indicated that there was no difference in drought tolerance and salt tolerance between indica and japonica mitochondria.4.According to the investigation of plant height,biomass,effective tillering,main panicle length,main panicle seed setting rate and other important agronomic traits of indica and japonica isonuclear alloplasmic populations under IRAT109 and NIP backgrounds in dry field,it was found that there were significant differences in plant height between indica and japonica isonuclear alloplasmic populations under IRAT109 background,but no significant differences in other traits.There were significant differences in effective tillers and seed setting rate between indica and japonica isonuclear alloplasmic populations in NIP background,but no significant differences in other traits.In conclusion,12 indica and japonica specific ORF were identified in this study.Among them,the prokaryotic expression of orf124 b,orf106e,orf84 k endemic to japonica and orf143a-1,orf108b-1,orf135 b endemic to indica can affect the drought tolerance and salt tolerance of Escherichia coli,and may have an effect on the drought tolerance and salt tolerance of rice,which needs to be further studied by transforming rice materials.By evaluating and comparing some drought tolerance and salt tolerance traits in indica and japonica isonuclear alloplasmic populations from IRAT109 and NIP backgrounds,we found that there were no significant differences in other phenotypic traits between indica and japonica isonuclear alloplasmic populations from two backgrounds,except for the root tip tropism between indica and japonica isonuclear alloplasmic populations.On the one hand,random drift of nuclear genome may affect phenotypic evaluation due to the small size of the isonuclear alloplasmic populations used in this study;On the other hand,it may also be because the physiological mechanisms of drought and salt tolerance phenotypes involved in this study were limited,and the mechanisms of drought and salt tolerance could not be thoroughly dissected.In the follow-up study,we need to increase the number of isonuclear alloplasmic lines,improve the experimental methods,and cover more targeted characters and phenotypes according to different mechanisms of drought and salt tolerance,so as to further study the role of indica and japonica mitochondria in rice drought and salt tolerance. |
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