Identification Of Banana Aux/IAA Family And Its Expression Analysis In P.indica-induced FocTR4 Resistance

Banana is one of the world’s four major fruits.The deteriorating natural environment,including drought,salinity,heat stress,cold wave,etc.and pests and diseases,negatively affact the development of the banana industry in recent years.Among that,Fusarium wilt,caused by Fusarium oxysporum f.sp.cubense(FocTR4),is regarded as one of the most devastating diseases of bananas globally.It is the most fundamental solution to improve existing varieties and select new banana variety with high yield,good flavor and resistance.Genetically modified transgenic breeding is an important way,for which conventional breeding in triploid banana is difficult.Excavating antioxidant genes is the first step.Piriformospora indica(P.indica)is a arbuscular mycorrhizal fungus that has been colonized in a variety of plants in recent years to enhance the plant’s systemic resistance to stress.In the previous study,it was found that P.indica colonized in’Tianbao jiao’ had a certain inhibitory effect on the development of the Fusarium wilt.The auxin of the plant was affected by FocTR4 and P.indica.Under this premise,it was done to the observation of phenotype,determination of auxin content and quantitative expression analysis of auxin-related genes in four groups,which include the control without anytreatment,the P.indica plant,the plant FocTR4 infected and the plant inoculated with P.indica and FocTR4.On the basis of the above analysis results,the genome identification of banana Aux/IAA gene family and bioinformatics analysis of all members were carried out.The expression patterns of different subgroups of some genes in phylogenetic tree under different treatments and stresses and its expression in P.indica-induced FocTR4 resistance were analyzed.The subcellular localization of the two members was verified.The main results of this study were as follows:1 Effects of P.indica and FocTR4 on the content of auxin and the expression of some auxin-related genes in bananaThe symptoms of FocTR4 in the P.indica ’Tianbao jiao’ is later compared with the non-P.indica plants.After two months,the auxin content of the colony(P+)was significantly higher than that of the control,and the plant infected by FocTR4(F+)was significantly lower than the plant inoculated with P.indica and FocTR4(PF).Expression of some auxin-related genes was significantly responsive to both fungal,and both fungi played an opposite role in the regulation of MaIAA(Ma04_g27640)and MaIAA(Ma10_g15080)gene expression.2 Identification of banana Aux/IAA family members,bioinformatics analysis and codon bias analysisThe banana Aux/IAA gene family members were screened and identified from genome level using bioinformatic methods.A total of 44Aux/IAA family members distributed in all the banana chromosomes except chromosome 1 were identified.The coding sequence of these genes ranges from 378 bp to 1 062 bp,encoding proteins with 125 ~ 353 aa.All of their encoded protein were hydrophilic proteins without signal peptide.Gene structure analysis showed that most members of the family shared 5 exons and 4 introns,and most of their encoded proteins contained 4 typical conserved motifs.Phylogenetic tree analysis revealed that the family members could be divided into two major categories and eight subgroups,and the same subgroup had similar gene structure and conserved motif.Subcellular location prediction results showed that the Aux/IAA members were mainly located in nucleus,cytoplasm and chloroplast.MaIAA31 was the only member of the family that predicted a transmembrane region and was located outside the extracellular.According to the genomic database analysis,9 members had variable splicing and some were verified.The genetic codon bias of the banana Aux/IAA gene family was weak.Preferred codons and optimal codons differed greatly from the banana genome.Codon bias of banana Aux/IAA gene family was mainly affected by mutation pressure.On the basis of codon modification and optimization,the E.coli prokaryotic expression system was suitable as a heterologous expression system for the family members,and tobacco could be used as a genetic transformation receptor for the family.3 Prediction of cis-acting elements of banana Aux/IAA gene family members and quantitative analysis of some membersStatistics on the promoter cis-acting elements of all members of the banana Aux/IAA gene family revealed that several elements were responsive to phytohormones and light,abiotic and biotic stresses.Gene expression analysis of several Aux/IAA members under different phytohormone and stress treatments revealed that the expression of Aux/IAAs had certain correlation with promoter elements and was also regulated by multiple factors.Meanwhile,several Aux/IAA members responded to various phytohormone and stress treatments to some extent and had significant responses in the early stage of FocTR4 infection,indicating that they might contribute to the stress responses of banana.4 Expression analysis of some members of banana Aux/IAA family in P.indica-induced FocTR4 resistanceBy analyzing the early expression profilings of some Aux/IAA members in response to FocTR4 infection,we found that most of the Aux/IAA members responded positively to FocTR4 and the up-regulation in the P.indica plant was significantly higher than that of non-P.indica colonization plants after 51 h,indicating that the banana Aux/IAA family played an important role in P.indica-induced resistance to FocTR4.5 The subcellular localization analysis of MaIAA25 and MaIAA31The subcellular localization was verified by constructing greenfluorescent protein fusion vector and injecting the onion epidermis.The results showed that MaIAA25 protein was mainly located in the nucleus,and MaIAA31 protein was mainly located extracellularly,which was consistent with the predicted results.