# High-Quality Assembly of the Apple Fungal Pathogen Marssonina coronaria Genome and Functional Analysis of Candidate Effectors

## TL;DR

This study provides a high-quality genome for the apple pathogen Marssonina coronaria and identifies key proteins that help it infect apple plants.

## Contribution

The paper presents a high-quality genome assembly and functional analysis of candidate effector proteins in M. coronaria.

## Key findings

- Eight CEPs suppressed BAX-induced cell death in N. benthamiana.
- McNLP1 and McCEP3 were identified as cell death-inducing effectors.
- McCEP3 homolog VmMcCEP3 also induced cell death independently of BAK1/SOBIR1.

## Abstract

Marssonina coronaria is the causal agent of apple blotch, which poses a significant threat to apple production worldwide. Here, Illumina and Oxford Nanopore sequencing were combined to generate a high-quality M. coronaria YL1 genome assembly (54.5 Mb, 23 contigs). Based on genome annotation, 97 candidate effector proteins (CEPs) were identified, and 61 CEPs were successfully cloned for functional analysis. Transient expression assays in Nicotiana benthamiana revealed that eight CEPs significantly suppressed BAX-induced cell death, with McCEP12, McCEP23, McCEP24, and McCEP52 concurrently inhibiting flg22-triggered reactive oxygen species bursts. Two signal peptide-dependent cell death-inducing effectors were identified: McNLP1, containing an NPP1 domain, and McCEP3. McCEP3 exhibited evolutionary conservation within Ascomycota, with its homologous gene VmMcCEP3 from Valsa mali inducing cell death in N. benthamiana. McEP03-triggered cell death was independent of BAK1/SOBIR1 receptor kinases. This study provides a high-quality genomic resource for M. coronaria and sheds light on the mechanisms by which its CEPs modulate host immunity, offering new insights into the molecular interactions between the pathogen and its host.