Anatomical And Physiological Changes And Salt Tolerance Gene Mining Of Eleusine Coracana Under Salt Stress

Due to natural factors and unreasonable irrigation,the area of saline alkali land is increasing year by year.Therefore,it is urgent to improve and utilize saline alkali land.As an annual food crop,Eleusine coracana（L.）Gaertn.has a certain salt tolerance.It has important value in feeding,edible,medicinal and environmental improvement.In this paper,we explored the changes of anatomical structure and physiological indexes of Eleusine coracana under salt stress,and explored the salt tolerance related genes through transcriptome sequencing.In this experiment,the seedlings were treated with 300 m M salt and divided into six time points（0 h,6 h,12 h,24 h,48 h,96 h）.A total of 8,777 differentially expressed genes were screened in leaves transcriptome and 8,150 differentially expressed genes were screened in roots transcriptome.GO annotation and KEGG pathway analysis of differentially expressed genes showed that up-regulated genes in leaves were mainly enriched in starch and sucrose metabolism,oxidative phosphorylation,plant hormone signal transduction and other pathways,down regulated genes in leaves were mainly enriched in photosynthesis,photosynthetic carbon fixation,photosynthetic antenna protein,porphyrin and chlorophyll metabolism and other pathways;up regulated genes in roots were mainly enriched in ribosome,Down regulated genes in roots are mainly enriched in plant hormone signal transduction,plant pathogen interaction,phenylpropane biosynthesis and other pathways.The changes of anatomical structure of leaves and roots were observed by paraffin section technique.It was found that the number of chloroplast decreased in leaves and the aerenchyma formed in roots after salt stress.The results showed that chlorophyll content,stomatal opening,intercellular CO₂concentration,transpiration rate and net photosynthetic efficiency decreased significantly under salt stress.Through transcriptome analysis,we found that the up-regulated expression of PP2C led to stomatal closure;the up-regulated expression of chlorophyllase gene led to chlorophyll decomposition;the down regulated expression of PPDK and PEPC led to the decrease of CO₂fixation efficiency;The down-regulation of Lhca and Lhcb resulted in the decrease of light harvesting efficiency.The contents of proline,soluble sugar and soluble protein in leave and roots were increased.Due to the large expression of the key gene（P5CS）in the glutamate pathway,proline biosynthesis is promoted;in sucrose and starch metabolism,genes related to mannose,galactose and fructose synthesis are up-regulated,resulting in the increase of soluble sugar content in plants.The accumulation of osmotic adjustment substances is beneficial to reduce the osmotic potential of plant cells and improve the water holding capacity of cells.Under salt stress,plants produce a lot of reactive oxygen species,which lead to membrane lipid peroxidation and malondialdehyde（MDA）,which aggravates membrane damage.The activities of SOD,POD and CAT increased in the early stage of stress,which was conducive to eliminating excessive reactive oxygen species in the body.With the extension of treatment time,the antioxidant enzyme system was destroyed,and the antioxidant enzyme activity decreased.A large number of reactive oxygen species caused serious damage to plants.Using the anatomical structure and physiological changes under salt stress and transcriptome analysis,the salt tolerance related genes were found,which provided the basis for improving the salt tolerance of plants.