Physiochemical Property And Transcriptomic Studies On The Roots Of Sensitive And Tolerant Switchgrass In Response To Alkaline Stress

Soil salinization seriously restricts global agricultural production,livestock breeding and ecological environment construction.As an important ethanol bioenergy plant,switchgrass(Panicum virgatum L.)was considered as one of the ideal plants to alleviate soil salinization,and can still grow well in saline-alkali soil and marginal soil.In our study,two strains of sensitive and tolerant of switchgrass were used as experimental materials,and root samples of 0 h,6 h and 24 h were selected for transcriptome sequencing based on the change nodes of physiological indexes.The differentially expressed genes and significantly enriched metabolic pathways in response to alkali treatment were compared between the two strains,and the physiological data and transcriptome data were integrated using the WGCNA method to further explore the possible molecular mechanism of the alkali resistance in switchgrass.The conclusions were as follows:(1)Two strains showed three distinct stress points(0 h,6 h,24 h)during the alkaline stress process,and were subjected to transcriptome analysis.In transcriptome sequencing,six different c DNA libraries were constructed and 114.03 Gb Clean Data was obtained.After assembly,we obtained 108,319 unigenes.By comparing the functions of NR,Swiss-Prot,KEGG,COG,KOG,GO and Pfam databases,the results showed that 63,663 non-redundant unigenes obtained annotation information,which had the highest similarity with the known proteins in NR databases(96.09%),among which the unigenes on Setaria italica accounted for the most(40.56%).(2)When the two strains were not stressed,1492 genes expressed were mainly concentrated in ribosome and phenylalanine metabolic pathways.when the two strains were stressed for 6 and 24 hours,413 differentially expressed genes were mainly concentrated in starch and sucrose metabolic pathway,valine,leucine and isoleucine degradation pathway and plant hormone signal transduction pathway,etc.After alkali treatment for 6 h and 24 h,the alkali-sensitive variety AM-314/MS-155 had 7727 differentially expressed genes at 6 h(S0/S6)and 5238 differentially expressed genes at 24 h of alkaline stress,and KEGG showed a major enrichment in the pathways of ribosomes,oxidative phosphorylation,glycolysis/gluconeogenesis and so on.After the alkali-tolerant variety Alamo was stressed,there were 1413 differentially expressed genes at 6 h(T0/T6)and 4443 differentially expressed genes at 24 h(T0/T24).KEGG showed that they were mainly enriched in plant-pathogen interaction,ubiquitin mediated proteolysis and glycolysis/gluconeogenesis pathways.The differentially expressed genes of alkali-sensitive variety were mainly concentrated in the early stage of stress,while the alkali-tolerant variety showed greater advantages in the late stage of stress.(3)ITAK software was used to predict 1480 transcription factors including b ZIP,b HLH,C2H2 and NAC,involving 64 transcription families,1718 protein kinases including Ca MK,CDPK,MAPK and RLK,and 577 transcription regulators.We finally identified 30 specifically expressed transcription factors in Alamo,with functional predictions focused on b ZIP,NAC,and MYB transcription factors.Three modules(lightsteelblue1,white,blue)were identified by WGCNA analysis,which represented the up-regulation of the alkali-tolerant variety Alamo at 6 h and 24 h and the higher correlation with REC.We screened 17 highly relevant hub genes that were mainly enriched in plant hormone signaling transduction and nitrogen metabolism pathways.(4)15 co-expressed genes were randomly selected for q RT-PCR verification.The results showed that 10 of the 15 tested transcripts had the same expression pattern as the results of RNAseq,and the expression level of q RT-PCR results was significantly correlated with the RNA-seq.