Project description:Plant-released flavonoids induce the transcription of symbiotic genes in rhizobia and one of the first bacterial responses is the synthesis of so called Nod factors. They are responsible for the initial root hair curling during onset of root nodule development. This signal exchange is believed to be essential for initiating the plant symbiosis with rhizobia affiliated with the alphaproteobacteria. Here, we provide evidence that in broad host range rhizobia the complete lack of quorum sensing molecules results in an elevated copy number of its symbiotic plasmid (pNGR234a). This in turn triggers the expression of symbiotic genes and the production of Nod factors in the absence of plant signals. Therefore, increasing the copy number of specific plasmids could be a widespread mechanism of specialized bacterial populations bridging gaps in signalling cascades and providing a competitive advantage.
Project description:Plant species posses a special set of genes functional only in arbuscular mycorrhizal symbiosis. So, the model plant Medicago truncatula (Jemalong 5) was used for transcriptome comparative analysis while infected with compatible rhizobia Sinorhizobium meliloti (strain 10) and with or without arbuscular mycorrhizal fungus Rhizophagus irregularis (SYM5). Whole shoot and whole root were used for RNA isolation and processed via one of the European certified Affymetrix core labs (http://core.img.cas.cz).
Project description:In this study, plants of maize inbred line B73 descended from two different sets of seed material grown for several generations either in the field or in the greenhouse were found to show a different growth phenotype and ionome under phosphate starvation conditions and moreover a different responsiveness towards mycorrhizal fungi of the species Glomus intraradices (syn: Rhizophagus irregularis).Transcriptome sequencing of three individuals from each set lent further support to the location of the introgression intervals and confirmed them to be fixed in all sequenced individuals. Moreover, we identified >120 genes differentially expressed between the two B73 lines.
Project description:Arbuscular mycorrhizal symbiosis is a predominant relationship between plant and arbuscular mycorrhizal fungi. To idendify arbuscular mycorrhiza responsive miRNAs, small RNA libraries were constructed in tomato roots colonized with Rhizophagus irregularis and without Rhizophagus irregularis. We identify miRNAs in tomato roots and provide a new profile of tomato miRNAs. And we found that some miRNAs were responsive to arbuscular mycorrhiza by comparing miRNAs in treatment with that in control. Examination of arbuscular mycorrhiza responsive miRNAs in tomato through high-throughput small RNA sequencing of roots with Rhizophagus irregularis and that without Rhizophagus irregularis
Project description:affy_med_2011_09: In natural ecosystems most vascular plants develop symbiosis with arbuscular mycorrhizal (AM) fungi which help them acquire nutrients such as phosphorus (P) and nitrogen (N). P has long been known to control AM symbiosis which takes place only when P is limiting. For N, however, its role in controlling mycorrhization is less clear. We have chosen the model plant Medicago truncatula to analyze the impact of P limitation and both P and N limitation on Medicago root transcriptome in response to the AM fungus Rhizophagus irregularis (formerly Glomus intraradices (BEG141)). These analyses may help us uncover signaling events involved in the interaction between these symbionts as well as genes encoding transporters potentially important for nutrient exchanges in these conditions. --We will compare the root transcriptome of Medicago truncatula plants inoculated with Rhizophagus irregularis to that of non-inoculated plants grown under P limitation (or both P and N limitation) after 4 weeks of culture 12 arrays - Medicago; wt vs mutant comparison
Project description:affy_med_2011_09: In natural ecosystems most vascular plants develop symbiosis with arbuscular mycorrhizal (AM) fungi which help them acquire nutrients such as phosphorus (P) and nitrogen (N). P has long been known to control AM symbiosis which takes place only when P is limiting. For N, however, its role in controlling mycorrhization is less clear. We have chosen the model plant Medicago truncatula to analyze the impact of P limitation and both P and N limitation on Medicago root transcriptome in response to the AM fungus Rhizophagus irregularis (formerly Glomus intraradices (BEG141)). These analyses may help us uncover signaling events involved in the interaction between these symbionts as well as genes encoding transporters potentially important for nutrient exchanges in these conditions. --We will compare the root transcriptome of Medicago truncatula plants inoculated with Rhizophagus irregularis to that of non-inoculated plants grown under P limitation (or both P and N limitation) after 4 weeks of culture
Project description:The quorum regulatory cascade is poorly characterized in Vibrio parahaemolyticus, in part because swarming and pathogenicity - the hallmark traits of the organism - are repressed by this scheme of gene control. As a consequence, many isolates appear silenced for quorum sensing via phase variation. In these studies, we examine a swarm proficient, virulent strain and find an altered function allele of the central quorum regulator luxO. We use this allele, which produces a constitutively active LuxO, to probe the upstream elements of the pathway and demonstrate their functionality for the first time. We find that the state of luxO affects expression of three small regulatory RNAS (Qrrs) and the activity of a translational fusion in opaR, the central output regulator. We use microarray profiling to determine the OpaR regulon, which was found to encompass ~5.2% of the genome. The quorum sensing proficient strain seems adapted for a sessile, community lifestyle; it is competent to uptake DNA, produces much capsular polysaccharide, has a high level of c-di-GMP, and strongly expresses one type six secretion system. Expressing the entire surface sensing regulon and numerous methyl accepting chemotaxis proteins, the quorum-disrupted cell type seems prepared for a mobile lifestyle. It is also cytotoxic to host cells in co-culture and expresses distinct type six as well as type three secretion systems. Thus, the scope and nature of the genes in the OpaR regulon provide many clues to the distinguishing traits of this Vibrio species as well as to the quite divergent survival strategies of the quorum ON/OFF phase variants
Project description:Paenibacillus polymyxa is an agriculturally important plant growth promoting rhizobacterium (PGPR). Many Paenibacillus species are known to be engaged in complex bacteria-bacteria and bacteria-host interactions, which in other bacteria were shown to necessitate quorum sensing communication, but to date no quorum sensing systems have been described in Paenibacillus. Here we show that the type strain P. polymyxa ATCC 842 encodes at least 16 peptide-based communication systems. Each of these systems comprises a pro-peptide that is secreted to the growth medium and further processed to generate a mature short peptide. Each peptide has a cognate intracellular receptor of the RRNPP family, and we show that external addition of P. polymyxa communication peptides to the medium leads to reprogramming of the transcriptional response. We found that these quorum sensing systems are conserved across hundreds of species belonging to the Paenibacillaceae family, with some species encoding more than 25 different peptide-receptor pairs, representing a record number of quorum sensing systems encoded in a single genome.