Genome-wide Identification Of VQ Gene Family In Fagopyrum Tataricum And Its Expression In Response To Leaf Spot Pathogens And Hormones

VQ protein is a kind of plant specific protein.As an auxiliary transcription factor,it is widely involved in many life activities such as plant growth,development,response to stress and so on.The whole genome data of Tartary buckwheat have been published in recent years,but the research on VQ gene family of Tartary buckwheat has not been reported.Based on the hidden Markov file of VQ conserved domain(pf05678),Hmmer 3.0 was used to compare and search the Tartary buckwheat genome database to identify VQ gene;The gene structure,chromosome distribution,promoter cis-elements,protein physicochemical properties,protein conserved motifs,protein subcellular localization and protein system evolution were analyzed by bioinformatics tools such as DNAMAN,Mapinspect,MEGA,MEME,Orthofinder and place;The expression patterns of VQ gene in Tartary buckwheat leaves infected by Alternaria alternata and Nigrospora osmanthi and affected by three defense related hormones salicylic acid(SA),methyl jasmonate(Me JA)and ethylene(ET)were analyzed by quantitative Real-Time PCR(q RT-PCR).It lays a foundation for in-depth analysis of the function and mechanism of Tartary buckwheat VQ gene family in plant disease resistance and defense,and provides clues for the exploration of excellent gene resources and the improvement of disease resistant varieties.The results are as follows:(1)A total of 28 VQ genes were identified in the genome of Tartary buckwheat,which did not contain chromosomes and were unevenly distributed on 8 chromosomes of Tartary buckwheat.Tartary buckwheat VQ protein can be divided into 6 kinds according to the hydrophobic amino acid h types in the VQ motif "fxxvqxhtg",namely FTG(Ft VQ7,Ft VQ19,Ft VQ20,Ft VQ22),ITG(Ft VQ21),VTG(Ft VQ23),ATG(Ft VQ27),YTG(Ft VQ2,Ft VQ10),and the other 19 are LTG.There was no VH mutation of glutamine(Q)to histidine(H)in Tartary Buckwheat VQ protein.(2)Subcellular localization prediction showed that among the 28 Tartary buckwheat VQ proteins,Ft VQ6,Ft VQ9,Ft VQ15,Ft VQ18,Ft VQ26 and Ft VQ28 were located in chloroplasts,Ft VQ14 was located in cytoplasm,and the other 21 were located in nucleus.Gene duplication analysis showed that there are 8 pairs of VQ parahomologous genes in Tartary buckwheat genome,including Ft VQ2-Ft VQ10,Ft VQ7-Ft VQ19,Ft VQ23-Ft VQ27,Ft VQ15-Ft VQ28,Ft VQ1-Ft VQ12,Ft VQ11-Ft VQ17,Ft VQ24-Ft VQ14 and Ft VQ4-Ft VQ9.All of which were large fragment duplication genes,suggesting that large fragment gene duplication played a major role in the quantitative expansion of Ft VQ gene family.The ratio of non synonymous mutation to synonymous mutation(Ka / Ks)is less than 1,suggesting that these gene pairs have experienced purification selection or negative selection in evolution.According to the protein amino acid sequence and conserved structural motif,Ft VQ protein is classified into five subfamilies,and the gene structure and protein motif in the subfamily are relatively conserved.(3)Promoter cis-element prediction showed that all Tartary buckwheat VQ gene promoters contained pathogenic response elements such as BIHD1OS、CGTCA、ERELEA4、W-box and W-box like,and hormone signal response elements such as SA,JA and ET,especially in the promoter regions of Ft VQ10,Ft VQ14,Ft VQ15,Ft VQ22,Ft VQ23 and Ft VQ27.(4)QPCR analysis showed that among the 20 detectable VQ genes of Tartary buckwheat,11 VQ genes were differentially expressed by A.alternata,of which 8 genes were up-regulated,and the up-regulated degree of Ft VQ10,Ft VQ14,Ft VQ22 and Ft VQ27 was the most significant.The other 3 genes whose expression was inhibited were Ft VQ3,Ft VQ9 and Ft VQ16.After inoculation with N.Osmanthi,11 of the 13 differentially expressed Tartary buckwheat VQ genes were up-regulated.The induction degree of Ft VQ10 was the highest and its expression increased 275.3 times at 12 hours after treatment.The other two down-regulated genes were Ft VQ39 and Ft VQ16;Fifteen VQ genes of Tartary buckwheat responded to SA treatment,and the differential expression trend of 10 genes was up-regulated.The degree of induction of Ft VQ10 was the most significant,and the expression was 533.7times at 24 hours;Under the treatment of Me JA,the expression of 13 VQ genes in Tartary buckwheat were induced and most of them were stably or continuously induced.The expression of one gene was significantly inhibited under the influence of Me JA;13 VQ genes responded to eth treatment,of which 12 genes were up-regulated,and only the expression level of Ft VQ17 was significantly down regulated.The results of expression analysis showed that most VQ genes of Tartary buckwheat responded to the infection of two leaf spot pathogens and three disease resistance related hormones,and most of the differential expression trends were up-regulated.