RESUMO
Xanthomonas phaseoli pv. manihotis (Xpm) is the causal agent of cassava bacterial blight, the most important bacterial disease in this crop. There is a paucity of knowledge about the metabolism of Xanthomonas and its relevance in the pathogenic process, with the exception of the elucidation of the xanthan biosynthesis route. Here we report the reconstruction of the genome-scale model of Xpm metabolism and the insights it provides into plant-pathogen interactions. The model, iXpm1556, displayed 1,556 reactions, 1,527 compounds, and 890 genes. Metabolic maps of central amino acid and carbohydrate metabolism, as well as xanthan biosynthesis of Xpm, were reconstructed using Escher (https://escher.github.io/) to guide the curation process and for further analyses. The model was constrained using the RNA-seq data of a mutant of Xpm for quorum sensing (QS), and these data were used to construct context-specific models (CSMs) of the metabolism of the two strains (wild type and QS mutant). The CSMs and flux balance analysis were used to get insights into pathogenicity, xanthan biosynthesis, and QS mechanisms. Between the CSMs, 653 reactions were shared; unique reactions belong to purine, pyrimidine, and amino acid metabolism. Alternative objective functions were used to demonstrate a trade-off between xanthan biosynthesis and growth and the re-allocation of resources in the process of biosynthesis. Important features altered by QS included carbohydrate metabolism, NAD(P)+ balance, and fatty acid elongation. In this work, we modeled the xanthan biosynthesis and the QS process and their impact on the metabolism of the bacterium. This model will be useful for researchers studying host-pathogen interactions and will provide insights into the mechanisms of infection used by this and other Xanthomonas species.
RESUMO
La secuenciación de transcritos con RNA-Seq es hoy en día una de las técnicas más populares en los estudios transcriptómicos. Relativamente reciente, esta técnica ha permitido la secuenciación de transcritos de RNA en una escala y profundidad no alcanzada por otras técnicas anteriores. Sin embargo, el alcance de las conclusiones que se pueden sacar depende estrictamente de un proceso adecuado, desde el diseño experimental hasta el análisis bioinformático de los datos. Dadas las diferencias en el proceso transcripcional de las células eucariotas y procariotas, el análisis de RNA-Seq deberá tener ciertas consideraciones dependiendo del tipo de organismo estudiado. En esta revisión se exponen los principales factores a tener en cuenta para lograr un análisis de RNA-Seq consistente, replicable y concluyente, enfocándose específicamente en organismos procariotas.
RNA-Seq is nowadays the method of choice for the sequencing of transcripts and transcriptomes in the field of molecular biology and gene expression assays. Until recently, this technique has allowed for the sequencing of RNA transcripts in an unprecedented scale and depth never reached in previous years; nevertheless, the reach and validity of the conclusions generated will depend strictly on an adequate experimental design and a robust analysis of the data. Given the inherent differences between prokaryotes and eukaryotes, the RNA-Seq analysis should take into account the type of organism studied. In this review we present the main factors to take into consideration when designing a consistent analysis for this type of data in prokaryotes, from the experimental design to the in silico analysis of the generated data.