Abstract
BackgroundThe potyviruses sugarcane mosaic virus (SCMV) and maize dwarf mosaic virus (MDMV) are major pathogens of maize worldwide. Two loci, Scmv1 and Scmv2, have ealier been shown to confer complete resistance to SCMV. Custom-made microarrays containing previously identified SCMV resistance candidate genes and resistance gene analogs were utilised to investigate and validate gene expression and expression patterns of isogenic lines under pathogen infection in order to obtain information about the molecular mechanisms involved in maize-potyvirus interactions.ResultsBy employing time course microarray experiments we identified 68 significantly differentially expressed sequences within the different time points. The majority of differentially expressed genes differed between the near-isogenic line carrying Scmv1 resistance locus at chromosome 6 and the other isogenic lines. Most differentially expressed genes in the SCMV experiment (75%) were identified one hour after virus inoculation, and about one quarter at multiple time points. Furthermore, most of the identified mapped genes were localised outside the Scmv QTL regions. Annotation revealed differential expression of promising pathogenesis-related candidate genes, validated by qRT-PCR, coding for metallothionein-like protein, S-adenosylmethionine synthetase, germin-like protein or 26S ribosomal RNA.ConclusionOur study identified putative candidate genes and gene expression patterns related to resistance to SCMV. Moreover, our findings support the effectiveness and reliability of the combination of different expression profiling approaches for the identification and validation of candidate genes. Genes identified in this study represent possible future targets for manipulation of SCMV resistance in maize.
Highlights
The potyviruses sugarcane mosaic virus (SCMV) and maize dwarf mosaic virus (MDMV) are major pathogens of maize worldwide
Symptom appearance was not tested for additional weeks, due to previous experience with the potyvirus pathosystem, where 100% infected plants of the susceptible genotype occur at later stages
CDNA microarray-based expression profiling SCMV experiment: within-time-point analysis 4578 observations for each of the five time points and the mock control were collected for pair-wise comparisons of near-isogenic genotypes, giving altogether 27468 observations across all time points. 65 sequences showed significant differential expression within time points and pair-wise contrasts at a false discovery rate (FDR) level of p ≤ 0.05
Summary
The potyviruses sugarcane mosaic virus (SCMV) and maize dwarf mosaic virus (MDMV) are major pathogens of maize worldwide. SCMV is notably harmful in Europe and China, MDMV in the southern US Corn Belt [3] Both closely related potyviruses are transmitted in a non-persistent manner by aphids mainly to members of the Poaceae family [4]. One major MDMV resistance gene (Mdmv1) mapped to the same region of chromosome 6S as Scmv. One major MDMV resistance gene (Mdmv1) mapped to the same region of chromosome 6S as Scmv1 It is not clear, whether or not Mdm and Scmv are the same or closely linked genes. The Scmv1/ Mdmv chromosome region contains a cluster of resistance gene analogues [4, 16], making both possibilities likely
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