Analysis Of Key Genes On Delaying Ripening Of Harvested Banana Treated With BTH Based On RNA-seq Technology

As an inducer,BTH,namely Benzothiadiazoleine,can induce systemic resistance in plants and improve plant resistance.Some studies have found that BTH treatment can delay the ripening of fruit,but there are few studies on the mechanism of delaying ripening and senescence of fruit.The effect and mechanism of BTH treatment on post-harvest fruit ripening of banana were studied with reference to the treatments of postharvest water and fungicides.Based on transcriptome sequencing RNA-seq technique,the differences of transcription level gene expr-ession in banana fruit at different stages after three treatments were compared and screened.In order to reveal the molecular mechanism of BTH delaying the ripeningof banana fruit,the differential gene expression trend in the key metabolic pathway of post-harvest process of banana was analyzed.The study of differential gene expression includes the following metabolic pathways including cell wall metabolism related to ripening and softening of banana fruit,stability of photosynthetic system related to degreening and color conversion of banana fruit,and active oxygen metabolism related to senescence of banana fruit.Associated with postharvest disease resistance,secondary metabolite synthesis,phenylpropane metabolic pathway,hormone signaling pathway,and the regulatory role of WRKY/NAC/MYB transcription factor.The main findings are as follows,1.BTH treatment obviously delayed the ripening process of banana fruit,delayed the yellowing of banana fruit,delayed the process of fruit softening,and maintained the firmness of the fruit.It can effectively inhibit the occurrence of anthracnose in storage time and improve the storage ability of banana fruit.2.The high throughput Illumina sequencing platform was used to sequence the fruit samples of three treatments at different stages,including the first day,the third day,the first day after ripening also as the fourth day after treatment.A total of 36425 genes were obtained,of which 8206 new genes were obtained,and the structure of 16601 genes was optimized.There were 10430 differentially expressed genes in the post-harvest process of the control fruit compared with the fruit at 0 day in the storage time,indicating that a large number of genes were involved in the ripening process of the fruit.Contrast to control,BTH treatment has 4179 differentially expressed genes.Among these genes,2488 genes were up-regulated and 1799 genes were down-regulated.There were 139 shared differentially expressed genes in every sample time,137 genes were up-regulated and 2 genes were down-regulated.Compared the fungicide treatment to control,there were 70 differentially expressed genes,among which 33 genes were up-regulated and 37 genes were down-regulated.But they don't have the same genes in different sample time.Compared BTH treatment with fungicide treatment,a total of 1533 differentially expressed genes were found,of which 1029 genes were up-regulated and 504 genes were down-regulated.They shared 86 genes differentially expressed in every sample time,which 81 genes were up-regulated and 5 genes were down-regulated.These results indicated that BTH could greatly induce the change of gene expression in banana fruit,thus inducing the fruit resistance and delaying fruit senescence,while the fungicide treatment had little effect on the gene expression in the fruit and only played a fungicidal effect.3.The proportion of TSS and TTS alternative spliced in banana is relatively high,accounting for about 33% and 36% of all the events respectively.Compared with control and fungicide treatment,the ratio of these in BTH treatment was about 1% higher than that in the other two treatments.4.After BTH treatment,the expression of chlorophyll synthesis-related genes in banana peel was significantly increased,the expression of genes related to cell wall degradation was significantly inhibited.The scavenging system of active oxygen species in banana pericarp was enhanced,including the up-regulated expression of related genes such as POD/PPO/GRX.BTH treatment also increased the expression of genes in the phenylpropane pathway and induced the expression of related genes of the PR-protein family.Furthermore,the Resistance Gene Analoga was significantly up-regulated.In summary,BTH treatment could maintain the stability of light system and active oxygen scavenging system,delay cell wall degradation,increase the accumulation of secondary metabolites,increase the accumulation of disease-resistant substances,then enhance the resistance of fruits,delay the process of fruit ripening and reduce the rotting caused by the interaction of disease and senescence,thus prolonging its shelf life.BTH treatment affected the expression of PYL,ERF,SAUR,JMT and other genes in the hormone signaling pathway,which affected the normal ripening process of fruits and increased the resistance of fruits.5.GO analysis showed that in the process of postharvest ripening,compared 1d with 0d on control treatment,the difference genes were significantly concentrated on the GO terms related to the photosynthetic system and the nucleotide metabolic system.After treatment with Ethylene,the difference genes were concentrated on the GO terms related to photosynthetic system,respiratory system,energy metabolism system,redox reaction and so on.Compared BTH treatment with control,the differentially expressed genes were mainly enriched in these GO terms,such as systemic acquired resistance and its regulation,defense response,innate immune response,fatty acid and lipid biosynthetic,photosystem I response center,photosynthetic member,thylakoid part and so on.Compared BTH treatment with fungicide treatment,the differential genes were not only enriched on GO terms related to systemic acquired resistance,defense and immunity,but also enriched on GO terms,such as purine purine nucleoside binding function,oxidoreductase activity and so on.There was no significant difference between control and fungicide treatment.6.KEGG analysis showed that in the process of postharvest ripening,compared 1d with 0d on control treatment,the difference gene was enriched in pathways related to photosynthesis,glycolic acid and two carboxylic acid metabolism,glycolysis/sugar isogenesis,carbon cycle,carbon fixation,biosynthesis of secondary metabolites,and so on.Compared with 3d and 0d,the difference genes were mainly enriched in pathways related to the biosynthesis of phenylalanine,tyrosine and tryptophan,phenylalanine metabolism,and biosynthesis of secondary metabolites.Compared with 4d and 0d,the difference genes were significantly enriched in the pathways of photosynthesis,photosynthesis,phosphorylation,carbon metabolism,carbon fixations.The different KEGG pathways between BTH treatment and control include such as ubiquinone and other terpene quinones biosynthesis,plant-pathogen interaction,plant hormone signal transduction,phenylpropanoid biosynthesis,phenylalanine metabolic pathway,peroxisome,biosynthesis and prolongation of fatty acids,photosynthetic antenna protein,photosynthesis and so on.The different KEGG pathways between BTH treatment and fungicide treatment include:ubiquinone and other terpene quinones biosynthesis,biosynthesis of phenylpropanoid,metabolic pathway of phenylalanine,Plant pathogen interactions,peroxisome,Valine/Leucine/Isoleucine degradation,Glutathione metabolisme.Compared fungicide treatment with control,the number of differentially expressed genes was little,and the number of pathways enriched was also limited,and the difference was not significant.7.BTH treatment significantly increased the expression of genes related to the MYB and WRKY families,especially MYB4/6/8/86/108 and WRKY40/41/60/63/67/70/71,while the NAC family genes were partly up-regulated and partly down-regulated.MYB family transcription factors were more closely related to secondary metabolism,while WRKY family transcription factors were more related to plant disease resistance.The results showed that BTH could reduce the occurrence of diseases in the storage time and delay the process of fruit ripening by enhancing the biotic and abiotic stress resistance of banana pericarp.