S and genes involved in the signal cascades associated with resistance
S and genes involved in the signal cascades associated with resistance and susceptibility. The response to F. oxysporum, as a vascular pathogen, has predominantly been characterized in the host/pathogen binomial tomato/ F. oxysporum f. sp. lycopersici which has become a model system for the molecular basis of disease resistance and susceptibility [25]. Some resistance mechanisms have been determined by gene silencing or insertional mutagenesis [18,2,26,27]. Understanding susceptibility/resistance in melon PubMed ID:https://www.ncbi.nlm.nih.gov/pubmed/26509685 would facilitate the development of new control strategies and the identification of pathogen and host factors required for resistance responses and/or disease progression. Changes in host and pathogen steady state mRNA levels during a fungal infection can provide a valuable readout of the molecular processes underlying resistance and susceptibility [28]. DNA microarrays are traditionally the standard tool for genome-wide expression analysis, although next-generation sequencing technologiesSestili et al. BMC Genomics 2011, 12:122 http://www.biomedcentral.com/1471-2164/12/Page 3 ofare emerging as a robust alternative, but in both cases large collections of known transcript sequences must already be available [29]. In contrast, cDNA-AFLP remains the method of choice where the focus is gene discovery, particularly when dealing with plant-microbe interactions and seeking to identify transcripts from both interacting partners [30,31]. Here we describe the identification of differentially expressed transcripts in the binomial interaction between melon and FOM. The cultivar Charentais Fom2 was chosen as the host genotype since it is susceptible to FOM race 1,2 but resistant to race 1, thus providing the opportunity to investigate both compatible and an incompatible interactions in the same genetic background. We infected plants with FOM strain ISPaVe1070 (race 1) and strains ISPaVe1018 and ISPaVe1083 (race 1,2 w). The race 1,2 w strains are both highly virulent, but only ISPaVe1083 commonly induces necrosis at the collar level. These strains were chosen to identify possible differences in gene expression between isolates differing in their aggressiveness. Host colonization in stems was assessed at 1, 2, 4, 8, 14, 16, 18 and 21 days post inoculation (dpi), and the fungal strains were reisolated from infected plants. We observed markedly different colonization patterns when comparing compatible and incompatible host-pathogen combinations. Five time points (0, 2, 4, 8 and 21 days) from the symptomless early stage (2 dpi) to obvious wilting symptoms (21 dpi) were considered for cDNAAFLP analysis to identify both early signaling events occurring in the plant, and plant or fungal genes possibly involved in symptom development. Because of the increase in fungal mass at late time points, the analysis was expected to identify a large number of fungal transcripts expressed in planta, particularly at 21 dpi, when wilting symptoms in the compatible interaction are obvious. RNA from colonies of the three strains grown in vitro was also included in the analysis to help detect FOM transcripts specifically expressed in Q-VD-OPh web planta and to identify transcript-derived fragments (TDFs) that are differentially expressed among races/strains.100 90 80 70 60 50 40 30 20 10Reisolation frequency ( ) ationISPaVe1070, avirulenta a ab ab ab ab b b1100 90 80 70 60 50 40 30 20 10Reisolation frequency ( ) solation )ISPaVe1083, virulentbc b babc cc c1100 90 80 70 60 50 40 30 20.