ABSTRACT
Reverse transcription-quantitative PCR (RT-qPCR) is an analytical tool for gene expression quantification. Reference genes are not yet available for gene expression analysis during interactions of Ralstonia solanacearum with 'Hawaii 7996' (the most stable source of resistance in tomato). Here, we carried out a multi-algorithm stability analysis of eight candidate reference genes during interactions of 'Hawaii 7996' with one incompatible/avirulent and two compatible/virulent (= resistance-breaking) bacterial isolates. Samples were taken at 24- and 96-h post-inoculation (HPI). Analyses were performed using the ∆∆Ct method and expression stability was estimated using BestKeeper, NormFinder, and geNorm algorithms. TIP41 and EF1α (with geNorm), TIP41 and ACT (with NormFinder), and UBI3 and TIP41 (with BestKeeper), were the best combinations for mRNA normalization in incompatible interactions at 24 HPI and 96 HPI. The most stable genes in global compatible and incompatible interactions at 24 HPI and 96 HPI were PDS and TIP41 (with geNorm), TIP41 and ACT (with NormFinder), and UBI3 and PDS/EXP (with BestKeeper). Global analyses on the basis of the three algorithms across 20 R. solanacearum-tomato experimental conditions identified UBI3, TIP41 and ACT as the best choices as reference tomato genes in this important pathosystem.
Subject(s)
Genes, Plant , Ralstonia solanacearum/genetics , Real-Time Polymerase Chain Reaction/methods , Algorithms , Gene Expression Regulation, PlantABSTRACT
We report here the complete genome sequences of two Ralstonia pseudosolanacearum strains, isolated from the warm northeast region of Brazil. They display divergent (compatible versus incompatible) interactions with the resistant tomato line Hawaii 7996. Polymorphisms were detected in a subset of effector genes that might be associated with these contrasting phenotypes.
ABSTRACT
The epidemic situation of Moko disease-causing strains in Latin America and Brazil is unclear. Thirty-seven Ralstonia solanacearum strains from Brazil that cause the Moko disease on banana and heliconia plants were sampled and phylogenetically typed using the endoglucanase (egl) and DNA repair (mutS) genes according to the phylotype and sequevar classification. All of the strains belonged to phylotype II and a portion of the strains was typed as the Moko disease-related sequevars IIA-6 and IIA-24. Nevertheless, two unsuspected sequevars also harbored the Moko disease-causing strains IIA-41 and IIB-25, and a new sequevar was described and named IIA-53. All of the strains were pathogenic to banana and some of the strains of sequevars IIA-6, IIA-24, and IIA-41 were also pathogenic to tomato. The Moko disease-causing strains from sequevar IIB-25 were pathogenic to potato but not to tomato. These results highlight the high diversity of strains of Moko in Brazil, reinforce the efficiency of the egl gene to reveal relationships among these strains, and contribute to a better understanding of the diversity of paraphyletic Moko disease-causing strains of the R. solanacearum species complex, where the following seven distinct genetic clusters have been described: IIA-6, IIA-24, IIA-41, IIA-53, IIB-3, IIB-4, and IIB-25.
