Molecular response of resistant and susceptible apple genotypes to Erwinia amylovora infection

Abstract

The leaves of apple cultivars resistant (cv. Free Redstar) and susceptible (cv. Idared) to fire blight were infiltrated with Erwinia amylovora. After 24 hours, differential gene expression was analysed using cDNA-AFLP technique. The expression pattern in the resistant cultivar, especially up-regulated genes encoding proteins involved in hypersensitive reaction and controlled cell death (BAX inhibitor and HIR protein), support the hypothesis that hypersensitive reaction is the main mechanism of resistance to fire blight in cv. Free Redstar. An important role in the resistance reaction is also played by proteins involved in signal transduction, especially serine/threonine kinase, which has been shown previously to confer resistance to fungal and bacterial pathogens in a number of plant species. A potential role in the defence against Erwinia amylovora was probably also β-1,3-glucanase (PR-2 protein), which was up-regulated in the resistant cultivar only. One of the proteins known to be involved in plant defense against pathogens -glutamate receptor -was up-regulated in the leaves of cv. Idared. Although the susceptible phenotype of this cultivar shows that expression of glutamate receptor only does not provide substantial resistance, it may be considered in gene pyramiding in apple breeding programmes.

Comparative transcriptome analysis of a lowly virulent strain of Erwinia amylovora in shoots of two apple cultivars – susceptible and resistant to fire blight

“…Several QTLs (Quantitative Trait Loci) related to resistance to fire blight in different apple genetic backgrounds and in response to different E. amylovora strains have been found [reviewed in [ 29 ]. Comparative studies of the reaction of sensitive and resistant apple cultivars to E. amylovora infection have revealed higher expression of a gene encoding vacuolar processing enzyme (VPE) - a caspase-like protease active during programmed cell death [ 30 ], BAX inhibitor and HIR proteins involved in hypersensitivity reactions and controlled cell death, and proteins involved in signal transduction, especially serine/threonine kinase and β-1,3-glucanase (PR-2 protein) [ 31 ]. Milcevičová et al [ 32 ] indicated that the resistant plants might represent a less favourable environment for bacterial growth and have higher levels of some defence-related compounds, such as salicylic acid, or increased activities of these compounds, such as the PAL enzyme.…”

Apple Autotetraploids with Enhanced Resistance to Apple Scab (Venturia inaequalis) Due to Genome Duplication-Phenotypic and Genetic Evaluation

“…To evaluate the genetic background of phenotypic alterations between apple ‘Free Redstar’ neotetraploids and their diploid counterparts, we determined the presence of various Rvi genes using cDNA-AFLP (amplified fragment length polymorphism) analysis, as well as examined the differential expression of Rvi6 gene and other resistance-related genes, such as PR1 (pathogenesis-related protein 1), PR2 (β-1,3-glucanase), WRKY29 (WRKY transcription factor 29), CDPK (calcium-dependent protein kinase), and MPK4 (a mitogen-activated protein kinases). Previously, we successfully used cDNA-AFLP analysis to identify the resistance-related genes in Malus × domestica and Prunus domestica under infection by Erwinia amylovora and the Plum pox virus , respectively [ 29 , 30 ].…”