Transcriptomics comparisons of efficient or inefficient rhizobia during the simbiosis with Medicago truncatula

PÉREZ GIMÉNEZ, JULIETA; JESUS MONTIEL; HANNA BEDNARZ; EVA KONDOROSI; DANIEL WIBBERG; RUI LIMA; ANDREAS SCHLÜTER; KARSTEN NIEHAUS; TORRES TEJERIZO, GONZALO A.; ANIKA WINKLER; ATTILA FARKAS; ALFRED PÜHLER

Estocolmo

Conferencia; 13th European Nitrogen Fixation Conference; 2018

The Medicago-rhizobia symbiosis is a very complex process. After an initial signal exchange among the rhizobia and the leguminous plant, the bacteria are able to invade the plant. The production of specific compounds, such as flavonoids by the plant and nodulation factors by the bacteria, play a critical role in the specificity of the interaction. During the invasion, the bacteria evade several host-plant barriers until it differentiates in bacteroids. These bacteroids are responsible for the achievement of a successful N2-fixation. The plant produce many signals involved in the overall process, e.g. nodule-specific cysteine-rich (NCR) peptides were described as key molecules for the bacterial differentiation. NCR peptides are released by the plant are targeted to the bacteria(1). With the aim of detect new bacterial genes involved in the late-stages of the communication, transcriptomics approaches were done.We employed the model rhizobia Ensifer meliloti 2011, as an example of an efficient rhizobia, and Rhizobium favelukesii LPU83(2), as an ineffective rhizobia for N2-fixation. The nodules developed by R. favelukesii were not fully differentiated; a higher number of viable bacteria were recovered per nodules and the bacteria never elongate inside the nodules. Bacteria transcriptomes were obtained from free-living cultures and at 10 or 31 days post-inoculation. We compared the transcriptomics profiles inside/outside the nodules, in which both strains showed almost 4000 genes that are changing.We determinate the set of orthologues genes between both bacteria (3450 genes) and compared the expression profiles of these orthologues genes. A set of 514 genes showed less expression in the inefficient rhizobia than in E. meliloti, mainly genes involved in metabolic pathways. On the other hand, 1606 genes showed more expression in R. favelukesii, these genes are mainly involved in transcriptomic and translation processes. Many of the detected genes are already described as relevant for the symbioses, nevertheless new determinants, classified as hypothetical were found. The identification of new determinants involved in the symbiotic process will lead to go further in the comprehension of an efficient N2-fixation interaction.