Responses of Fuji (Malus domestica) and Shandingzi (Malus baccata) apples to Marssonina coronaria infection revealed by comparative transcriptome analysis

Abstract

Marssonina leaf blotch of apple caused by Marssonina coronaria is one of the most important diseases of apple (Malus domestica) worldwide. Breeding and the appropriate utilization of disease-resistant varieties is the safest, most effective, most economical and environmentally friendly method for controlling the disease. Previous studies have demonstrated that Shandingzi (Malus baccata) is much more resistant to M. coronaria than Fuji (M. domestica). However, the molecular mechanisms of Fuji and Shandingzi resistance to M. coronaria infection remain unknown. In this study, the responses of Fuji and Shandingzi to M. coronaria infection were studied by comparative transcriptome analysis. As a result, 4898 and 2897 differentially expressed genes (DEGs) in Fuji and Shandingzi, respectively, were identified. Gene Ontology (GO) enrichment analysis of the co-expressed DEGs showed that 25 significant terms were enriched, and the unique DEGs in Shandingzi were mainly associated with the biotic stimulus response (GO: 0009607), defense response (GO: 0006952), stress response (GO: 0006950) and oxidoreductase activity (GO: 0016491). Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that the DEGs in both species of Rosaceae were enriched in plant-pathogen interactions, amino acid metabolism and other pathways. In the plant-pathogen interaction pathway, mitogen-activated protein kinase and Ca2+ signaling pathways were induced and enriched in both Shandingzi and Fuji when infected by M. coronaria. Furthermore, the percentages of R genes and disease resistance-related DEGs in Shandingzi were higher than those in Fuji. The qRT-PCR analysis results were consistent with the transcriptome results. The results provide a theoretical basis for breeding disease-resistant varieties.