Proteome Analysis of Pathogen-Responsive Proteins from Apple Leaves Induced by the Alternaria Blotch Alternaria alternata

Abstract

Understanding the defence mechanisms used by apple leaves against Alternaria alternate pathogen infection is important for breeding purposes. To investigate the ultrastructural differences between leaf tissues of susceptible and resistant seedlings, in vitro inoculation assays and transmission electron microscopy (TEM) analysis were conducted with two different inoculation assays. The results indicated that the resistant leaves may have certain antifungal activity against A. alternate that is lacking in susceptible leaves. To elucidate the two different host responses to A. alternate infection in apples, the proteomes of susceptible and resistant apple leaves that had or had not been infected with pathogen were characterised using two-dimensional electrophoresis (2-DE) and matrix-assisted laser desorption/ionisation time-of-flight tandem mass spectrometry (MALDI-TOF-TOF MS). MS identified 43 differentially expressed proteins in two different inoculation assays. The known proteins were categorised into 5 classes, among these proteins, some pathogenesis-related (PR) proteins, such as beta-1,3-glucanase, ascorbate peroxidase (APX), glutathione peroxidase (GPX) and mal d1, were identified in susceptible and resistant hosts and were associated with disease resistance of the apple host. In addition, the different levels of mal d1 in susceptible and resistant hosts may contribute to the outstanding anti-disease properties of resistant leaves against A. alternate. Taken together, the resistance mechanisms of the apple host against A. alternate may be a result of the PR proteins and other defence-related proteins. Given the complexity of the biology involved in the interaction between apple leaves and the A. alternate pathogen, further investigation will yield more valuable insights into the molecular mechanisms of suppression of the A. alternate pathogen. Overall, we outline several novel insights into the response of apple leaves to pathogen attacks. These findings increase our knowledge of pathogen resistance mechanisms, and the data will also promote further investigation into the regulation of the expression of these target proteins.

Transcriptomics Analysis of Apple Leaves in Response to Alternaria alternata Apple Pathotype Infection

“…HSP20s , for example, did not respond at early stages of infection but slightly increased at later stages. In contrast, many of HSP70 transcripts were down-regulated (Figure 8B), a result confirmed by a proteomics study of apple-AAAP interactions that showed that these proteins accumulate in resistance as opposed to susceptible leaves (Zhang et al, 2015). Additional research has shown that HSP70s are induced by both P. expansum and P. digitatum pathogens in “Ultima Gala” apple cultivar (Spadoni et al, 2015), thus expression of these proteins is an important fact of apple disease-resistance.…”

Alternaria Toxins: Potential Virulence Factors and Genes Related to Pathogenesis

“…On the basis of AM-toxin acting site and known pathogenesis, it is identified that Alternaria alternata f. sp. mali pathogen may secrete AM-toxins that act on the susceptible leaf cells causing tissues damage (Zhang et al, 2015 ).…”

A Single-Nucleotide Polymorphism in the Promoter of a Hairpin RNA Contributes to Alternaria alternata Leaf Spot Resistance in Apple (Malus × domestica)

“…Alternaria alternata leaf spot is a major fungal disease of apple (Malus × domestica). (Zhang et al, 2015). In general, when fungi attack apple leaves, they produce toxins and effectors, which disrupt plant metabolism (Hugot et al, 1999;Johnson et al, 2000;Abe et al, 2010), leading to H 2 O 2 accumulation and cell death (Chung, 2012).…”