Role of calcium dependent protein kinases (CDPKs) in resistant and susceptible cultivars of Malus x domestica in response to the pathogen Erwinia amylovora

Plant calcium (Ca2+) signals are involved in a wide array of intracellular signaling pathways after pathogen invasion. Ca2+-binding sensory proteins such as Ca2+-dependent protein kinases (CDPKs) have been predicted to mediate the signaling following Ca2+ influx after pathogen infection. However, until now this prediction remains elusive. We conducted a genome-wide analysis of Malus x domestica CDPKs and identified 30 CDPK genes. Malus CDPKs were found to be similar to their counterparts in Arabidospis thaliana in gene structure and subgroup classification. Furthermore, comparative quantitative real-time RT-PCR and intracellular cytosolic calcium analysis were conducted between a fire blight resistant and susceptible M. x domestica cultivar upon invasive pathogen (Erwinia amylovora) and/or mechanical damage. We found that there is striking difference between resistant and susceptible cultivars. Our genomic and bioinformatics analyses will provide important information about the M. x domestica CDPKs role in modulating the defense responses between the susceptible and resistant cultivars. It also sheds light for the further elucidation of early signaling and downstream signaling cascades for the pathogen and wound responses