Study On The Response Of Apple NBS-encoding Gene To Alternaria Alternata

The apple(Malus domestica)is a rosaceae apple tree.As apple has the advantages of strong cultivation adaptability,high fruit nutritional value,good storage stability,and can be used for the annual market.Apple has become one of the most consumed fruit types.Apple blotch is a worldwide fungal disease that occurs in apple growing regions around the world.The disease has a great negative impact on the quality and yield of apples.It often causes early defoliation.Therefore,it is of great practical significance to explore resistance genes for disease resistance breeding.As important pathogen-response genes,NBS genes have important significance for screening plants under different environmental conditions.In this paper,we analyzed the RNA-Seq data of the disease infected 'Starking' by Alternaria alternata and screened 19 differentially expressed NBS-encoding(Nucleotide-binding-site)genes.Through the physicochemical properties analysis,co-expression network construction,expression pattern analysis,and phylogenetic tree analysis of these 19 genes,core genes in the co-expression network(MDP0000210357,MDP0000240537,and MDP0000291205)were discovered.In addition,three genes(MDP0000259862,MDP0000304378 and MDP0000292810)were found to respond strongly to apple blotch.To study in depth the response of different apple varieties to A.alternata,we compared the morphological changes of two important apple cultivars 'Golden Delicious'and 'Starking' under the infection of A.alternata.The results showed that the 'Golden Delicious' appeared lesions earlier than the 'Starking',but the 'Starking' had more severe infection symptoms in the later stages of infection.Based on the qRT-PCR data,we studied the expression of 12 NBS-encoding genes in response to infection by A.alternata.In addition,we also investigated the gene structure,chromosomal location,and physicochemical properties of the encoded proteins of these 12 NBS-encoding genes.The gene expression after inoculation showed that 12 NBS-encoding genes were expressed differently in two apple cultivars.The two genes with the highest expression levels(MDP0000292810 and MDP0000127009)can be used as potential candidate genes for genetic improvement and directional selection of new disease-resistant apple germplasm.