| Salt stress will seriously affect the growth and yield of rice,and is one of the most common abiotic stresses in the growth and development of rice.With the continuous increase of saline-alkali land in the world,salt stress has become one of the major factors threatening the development of agriculture.In this paper,through the determination of physiological indexes related to salt stress at the germination and seedling stages and transcriptome sequencing of rice G178,the physiological characteristics of G178 salt tolerance were preliminarily analyzed,which also laid the foundation for the subsequent indepth identification of related genes and molecular mechanism research.The main findings are as follows:1.G178 has strong salt tolerance at germination stageUnder 150 mM and 200 mM NaCl salt stress at the germination stage,G178 has a higher relative germination rate and relative germination index,and the overall germination situation is better.The final germination rate is above 80% and can be sown normally.According to the relative salt damage classification standard based on germination rate,G178 has strong salt tolerance at the germination stage.In addition,after salt stress treatment for 10 days,although salt stress obviously inhibited the growth of G178 roots,its relative shoot length was significantly higher than that of the control material.Further measurement of its antioxidant enzyme activity and malondialdehyde content revealed that there was no significant change in SOD and POD activities of G178 at the germination stage under salt stress compared to the control,and its MDA content did not accumulate in a large amount compared with control,indicating that the degree of membrane lipid peroxidation damage to G178 is lower,and it has higher salt tolerance than the control material.2.G178 is tolerant to salt stress at the seedling stageG178 was treated with 150 mM NaCl salt stress at the seedling stage,and it was found that the wilting and yellowing of seeding leaf of G178 was lighter than control,and the survival rate after rewatering was as high as 81.6%,indicating that G178 is tolerant to salt stress at the seedling stage.In order to verify the specific physiological mechanism for salt tolerance of G178,physiological indexes such as chlorophyll content,photosynthetic rate,stomatal conductance,transpiration rate,antioxidant enzyme activity and MDA content were further determined.The results showed that although the photosynthetic rate of four varieties of rice seedlings dropped significantly,the decline was smaller compared to other varieties,and the photosynthetic rate was the highest among the four varieties under salt stress.Further analysis showed that salt stress had no significant effect on the total chlorophyll content of G178,stomatal conductance and transpiration rate of G178 were smaller than those of the control,and the activitiy of antioxidant enzyme such as SOD and POD in G178 seedlings increased significantly,thus ensuring that G178 seedlings could maintain under salt stress.This ensures that G178 seedlings can maintain a relatively high photosynthetic level under salt stress,reduce water loss,effectively remove active oxygen in the plant,and reduce the level of cell membrane lipid peroxidation,which is beneficial to improve the salt tolerance at the seedling stage,and better maintain the normal growth of G178 seedings.3.The salt tolerance of G178 is related to glutathione metabolism,amino acid and sugar metabolism pathwaysIn order to further understand the underlying molecular mechanism of salt resistance,transcriptome sequencing analysis was also conducted using the seeds at the germination stage of 36 hours under salt stress.The results showed that there were 356 differential genes before and after the salt stress treatment in G178 and the salt-tolerant control varieties YX156 with similar expression changes,but there was no change in ZS97 B.In addition,the study of genes whose expression levels change only in G178 is also of great significance,and there are 1,570 genes in total.The results of GO function annotation analysis showed that the GO items involving the largest number of differentially expressed genes in G178 were protein binding,ATP binding,oxidation-reduction process,metabolic process,protein phosphorylation,membrane and integral component of membrane.While the differentially expressed genes in G178 were mainly enriched in metabolic pathways,biosynthesis of secondary metabolites,and ribosome.In addition,glutathione metabolism,glycolysis/gluconeogenesis,cysteine and methionine metabolism pathways are enriched in G178,but not in the control material ZS97 B.It is speculated that the salt tolerance of G178 is related to the above three pathways. |
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