Bacterial intraspecies and interspecies communication in the rhizosphere is mediated by diffusible signal molecules. Many Gram-negative bacteria use N-acyl-homoserine lactones (AHLs) as autoinducers in the quorum sensing response. While bacterial signalling is well described, the fate of AHLs in contact with plants is much less known. Thus, adsorption, uptake and translocation of N-hexanoyl- (C6-HSL), N-octanoyl- (C8-HSL) and N-decanoyl-homoserine lactone (C10-HSL) were studied in axenic systems with barley (Hordeum vulgare L.) and the legume yam bean (Pachyrhizus erosus (L.) Urban) as model plants using ultra-performance liquid chromatography (UPLC), Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) and tritium-labelled AHLs. Decreases in AHL concentration due to abiotic adsorption or degradation were tolerable under the experimental conditions. The presence of plants enhanced AHL decline in media depending on the compounds' lipophilicity, whereby the legume caused stronger AHL decrease than barley. All tested AHLs were traceable in root extracts of both plants. While all AHLs except C10-HSL were detectable in barley shoots, only C6-HSL was found in shoots of yam bean. Furthermore, tritium-labelled AHLs were used to determine short-term uptake kinetics. Chiral separation by GC-MS revealed that both plants discriminated D-AHL stereoisomers to different extents. These results indicate substantial differences in uptake and degradation of different AHLs in the plants tested.
Arbuscular mycorrhizal (AM) symbiosis is heavily and positively implicated in phosphorus (P) acquisition from soil to plants, including many important agricultural crops. Its role in plant nitrogen (N) nutrition is generally not as prominent or beneficial, with exception of some situations when N is available predominantly in organic forms. Yet the AM fungi (AMF) are, due to their poor exo-enzymatic repertoire, unlikely to degrade organic compounds on their own, therefore they possibly depend on other microorganisms to liberate nutrients contained in those materials. Here, we review current knowledge on the roles played by the AMF in plant N nutrition in general and uptake of N from organic compounds in particular, with a specific reference to microbes and processes involved in liberation and AM fungal utilization of N from organic compounds. Future research needs and directions are outlined, as is the agronomic and societal context of such research.
SummaryBacteria communicate with each other in a population density-dependent process known as quorum sensing. N-acyl-homoserine lactones (HSLs) are the autoinducers of Gram-negative bacteria and the best-studied quorum sensing signals so far. HSLs induce various responses in plants, including systemic resistance and root development.Here, we used different methods, including tritium labelling, sensor strain assays and monoclonal antibodies (mAbs), to analyse the uptake and translocation of C8-and C10-homoserine lactones into barley (Hordeum vulgare cv Barke).Both HSLs were already systemically transported into the shoot at 2 h after application. HSL uptake could be inhibited by orthovanadate, demonstrating that ABC transporters are involved in the uptake. Root transport occurs predominantly via the central cylinder, which was shown by transport inhibition via KCl application and autoradiography of root cross-sections. Furthermore, a newly established detection method with mAbs allowed the first detection of a systemic transport of long-chain HSLs in plants.The coupled use of different HSL detection methods demonstrated that the uptake and transport of HSLs into barley does not occur passively, but relies, at least partially, on active processes in the plant.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.