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Publikationen - Molekulare Signalverarbeitung

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Budiharjo, A.; Chowdhury, S.M.; Dietel, C.; Beator, B.; Dolgova, O.; Fan, B.; Bleiss, W.; Ziegler, J.; Schmid, M.; Hartmann, A.; Borris, R. Transposon Mutagenesis of the Plant-Associated Bacillus amyloliquefaciens ssp. plantarum FZB42 Revealed That the nrfA and RBAM17410 Genes Are Involved in Plant-Microbe-Interactions PLOS ONE 9, e98267, (2014) DOI: 10.1371/journal.pone.0098267

Bacillus amyloliquefaciens ssp. plantarum FZB42 represents the prototype of Gram-positive plant growth promoting and biocontrol bacteria. In this study, we applied transposon mutagenesis to generate a transposon library, which was screened for genes involved in multicellular behavior and biofilm formation on roots as a prerequisite of plant growth promoting activity. Transposon insertion sites were determined by rescue-cloning followed by DNA sequencing. As in B. subtilis, the global transcriptional regulator DegU was identified as an activator of genes necessary for swarming and biofilm formation, and the DegU-mutant of FZB42 was found impaired in efficient root colonization. Direct screening of 3,000 transposon insertion mutants for plant-growth-promotion revealed the gene products of nfrA and RBAM_017140 to be essential for beneficial effects exerted by FZB42 on plants. We analyzed the performance of GFP-labeled wild-type and transposon mutants in the colonization of lettuce roots using confocal laser scanning microscopy. While the wild-type strain heavily colonized root surfaces, the nfrA mutant did not colonize lettuce roots, although it was not impaired in growth in laboratory cultures, biofilm formation and swarming motility on agar plates. The RBAM17410 gene, occurring in only a few members of the B. subtilis species complex, was directly involved in plant growth promotion. None of the mutant strains were affected in producing the plant growth hormone auxin. We hypothesize that the nfrA gene product is essential for overcoming the stress caused by plant response towards bacterial root colonization.

Poeschl, Y.; Delker, C.; Trenner, J.; Ullrich, K.; Quint, M. & Grosse, I. Optimized Probe Masking for Comparative Transcriptomics of Closely Related Species PLOS ONE 8, e78497, (2013) DOI: 10.1371/journal.pone.0078497

Microarrays are commonly applied to study the transcriptome of specific species. However, many available microarrays arerestricted to model organisms, and the design of custom microarrays for other species is often not feasible. Hence,transcriptomics approaches of non-model organisms as well as comparative transcriptomics studies among two or morespecies often make use of cost-intensive RNAseq studies or, alternatively, by hybridizing transcripts of a query species to amicroarray of a closely related species. When analyzing these cross-species microarray expression data, differences in thetranscriptome of the query species can cause problems, such as the following: (i) lower hybridization accuracy of probes dueto mismatches or deletions, (ii) probes binding multiple transcripts of different genes, and (iii) probes binding transcripts ofnon-orthologous genes. So far, methods for (i) exist, but these neglect (ii) and (iii). Here, we propose an approach forcomparative transcriptomics addressing problems (i) to (iii), which retains only transcript-specific probes binding transcriptsof orthologous genes. We apply this approach to an Arabidopsis lyrata expression data set measured on a microarraydesigned for Arabidopsis thaliana, and compare it to two alternative approaches, a sequence-based approach and a genomicDNA hybridization-based approach. We investigate the number of retained probe sets, and we validate the resultingexpression responses by qRT-PCR. We find that the proposed approach combines the benefit of sequence-based stringencyand accuracy while allowing the expression analysis of much more genes than the alternative sequence-based approach. Asan added benefit, the proposed approach requires probes to detect transcripts of orthologous genes only, which provides asuperior base for biological interpretation of the measured expression responses.
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