Local and systemic changes in expression of resistance genes, <it<nb-lrr</it< genes and their putative microRNAs in norway spruce after wounding and inoculation with the pathogen <it<ceratocystis polonica</it<

<p<Abstract</p< <p<Background</p< <p<NB-LRR resistance proteins are involved in recognizing pathogens and other exogenous stressors in plants. Resistance proteins are the first step in induced defence responses and a better understanding of their regulation is important...
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<p<Abstract</p< <p<Background</p< <p<NB-LRR resistance proteins are involved in recognizing pathogens and other exogenous stressors in plants. Resistance proteins are the first step in induced defence responses and a better understanding of their regulation is important to understand the mechanisms of plant defence. Much of the post-transcriptional regulation in plants is controlled by microRNAs (miRNA). We examined the expression of five Norway spruce miRNA that may regulate NB-LRR related transcripts in secondary phloem (bark) of resistant Norway spruce after wounding and inoculation with the necrotrophic blue stain fungus <it<Ceratocystis polonica</it<.</p< <p<Results</p< <p<The plants of this clone recovered from both the pathogen inoculations and wounding alone. We found local and systemic induction of the resistance marker genes <it<PaChi4, PaPAL</it< and <it<PaPX3</it< indicative of an effective induced host defence response. There were minor local and systemic changes in the expression of five miRNAs and 21 NB-LRRs between healthy and treated plants. Only five putative NB-LRRs (<it<PaLRR1, PaLRR3, PaLRR14, PaLRR15</it< and <it<PaLRR16</it<) showed significant increases greater than two-fold as a local response to <it<C. polonica</it<. Of all NB-LRRs only <it<PaLRR3</it<, the most highly differentially regulated NB-LRR, showed a significant increase also due to wounding. The five miRNAs showed indications of an initial local and systemic down-regulation at day 1, followed by a later increase up to and beyond the constitutive levels at day 6. However, the initial down-regulation was significant only for <it<miR3693</it< and <it<miR3705</it<.</p< <p<Conclusions</p< <p<Overall, local and systemic expression changes were evident only for the established resistance marker genes and <it<PaLRR3</it<. The minor expression changes observed both for the followed miRNAs and their predicted NB-LRR targets suggest that the expression of most NB-LRR genes are maintained close to their constitutive levels in stressed and healthy Norway spruce plants.</p< Ausführliche Beschreibung