mRNA extraction of Xanthomonas fragariae in strawberry and validation of reference genes for the RT-qPCR for study of bacterial gene expression.

This is the first study which describes a unique procedure of isolating of high-quality, intact RNA from strawberry leaves of Xanthomonas fragariae, three most suitable reference genes, crucial for the normalization of RT-qPCR data for this pathogen and accurate expression analysis of target genes. In our study, various mathematic algorithms: NormFinder geNorm, BestKeeper, the delta CT method, RefFinder were adopted for validation of most stable reference genes from nine candidate genes (ffh, glyA, gyrA, gyrB, proC, pykA, recA, rpoB, rpoD). The analyses allowing to select three most suitable pioneer reference genes, gyrB, ffh, and pykA, that we recommend for the normalization of RT-qPCR data and for the study of the expression of target genes in Xf. Moreover, their combination as references allowed for an accurate expression analysis and computation of the fold change of the flhF and iroN2 genes in Xf. These two genes are important for the success of the colonization of plant tissue and pathogenicity and sequences of primers designed to study these genes, are presented.