| Salt stress is one of the major factors limiting crop yield in the world.In China,salinized land is widely distributed,and approximately a quarter of the arable land area is affected by soil salinity.Moreover,the salinized land area is still increasing year by year.Rice is one of the most important staple food for about half of the world's population.However,rice is sensitive species to salt stress,and high salinity in the soil has a great impact on its yield.Therefore,to elucidate the molecular mechanism of rice salt tolerance is very important for production practice and fundamental research.Studying the function of Os NAC45 can provide important gene resources for the cultivation of salt-tolerant rice.NAC transcription factor is a unique gene family of plants.Current studies have found that NAC plays an important role in the whole life of plants,such as the growth and development of roots,the formation of apical meristem,the morphogenesis of flower organs,the senescence of leaves and abiotic stress resistance.Os NAC45 plays a key role in the response to salt stress.The study on the function of Os NAC45 can provide important genetic resources for the cultivation of salt-tolerant rice.In this study,we functionally characterized a transcription factor Os NAC45 in rice and got the following results:1.Quantitative real time PCR was used to analyze the expression level of Os NAC45 in different rice tissues.The results showed that Os NAC45 was expressed in roots,stems,leaves,leaf sheathes and spike,and the expression level was highest in roots and lowest in spike.Moreover,Na Cl can induce its expression in the roots.A time-course analysis of Na Cl-treated roots showed that the expression of Os NAC45 reached its highest level at 6 h.Additionally,the expression of Os NAC45 was induced by Na Cl in a dose-dependent manner.However,the expression of Os NAC45 was inhibited by ABA,and the effect was not dose-dependent.2.Both transient expression of Os NAC45 in rice protoplast cells and immunostaining in roots showed that Os NAC45 was located in the cell nucleus in rice.Moreover,transcriptional activation analysis showed that the full length of Os NAC45 had self-activation activity in yeast.3.Os NAC45 knockout and overexpression lines were obtained.In the presence of ABA,the germination and growth of the Os NAC45 overexpression seedlings were severely inhibited compared with the WT.On the contrary,the osnac45 seedlings germinated more quickly and grew faster than the WT,indicating that Os NAC45 participates in ABA signaling pathways during the germination and early growth of rice.4.The sensitivity of Os NAC45 knockout plants to salt stress was analyzed with hydroponic experiment,and the results showed that Os NAC45 knockout plants were more sensitive to salt stress compared with the wild type plants,indicating that Os NAC45 positive regulating the salt stress response in rice.NBT staining indicated that Os NAC45 knockout plants accumulated more ROS after salt treatment.5.The transcriptomes of mutants and wild-type Nipponbare under normal and salt stress conditions were analyzed using a high-throughput RNA-seq assay,and the expression levels of thousands of genes were up-regulated or down-regulated in the mutant plants compared with the wild type.And q RT-PCR analysis confirmed that the expression of Os CYP89G1? Os DREB1F? Os EREBP2? Os ERF104?Os SAMDC2?Os SIK1 and Os PM1 may be regulated by Os NAC45.In conclusion,our results demonstrated that Os NAC45 plays important roles in ABA signal responses and is required for rice salt tolerance through regulating expression level of stress-related genes,especially Os CYP89G1? Os DREB1F? Os EREBP2? Os ERF104?Os SAMDC2?Os SIK1 and Os PM1.These results provide key genetic resources for the development of salt-tolerant rice and have high practical value to solve the increasingly serious problem of world food shortage. |
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