Host genes involved in nodulation preference in common beans (Phaseolus vulgaris)-Rhizobium etli symbiosis revealed by suppressive subtractive hybridization

PELTZER-MESCHINI, E., F. A. BLANCO, M. E. ZANETTI, M. P. BEKER, H. KÜSTER, A. PÜHLER, AND O. MARIO AGUILAR

MOLECULAR PLANT-MICROBE INTERACTIONS

The International Society for Molecular Plant-Microbe Intera

Lugar: Knoxville; Año: 2008 vol. 21 p. 459 - 468

0894-0282

Common bean cultivars are nodulated preferentially byRhizobium etli lineages from the same center of host diversification.Nodulation was found to be earlier and numerousin bean plants inoculated with the cognate strain. Wepredicted that analysis of transcripts at early stages of theinteraction between host and rhizobium would identifyplant genes that are most likely to be involved in this preferentialnodulation. Therefore, we applied a suppressivesubtractive hybridization approach in which cDNA from aMesoamerican cultivar inoculated with either the more- orless-efficient strain of R. etli was used as the driver and thetester, respectively. Forty-one independent tentative consensussequences (TCs) were obtained and classified intodifferent functional categories. Of 11 selected TCs, 9 wereconfirmed by quantitative reverse-transcriptase polymerasechain reaction. Two genes show high homology to previouslycharacterized plant receptors. Two other upregulated genesencode for Rab11, a member of the small GTP-bindingprotein family, and HAP5, a subunit of the heterotrimericCCAAT-transcription factor. Interestingly, one of the TCsencodes for an isoflavone reductase, which may lead to earlierNod factor production by specific strains of rhizobia.The transcript abundance of selected cDNAs also wasfound to be higher in mature nodules of the more efficientinteraction. Small or no differences were observed when anAndean bean cultivar was inoculated with a cognate strain,suggesting involvement of these genes in the strain-specificresponse. The potential role of these genes in the earlypreferential symbiotic interaction is discussed.