Transgenic tomato plants alter quorum sensing in plant growth‐promoting rhizobacteria

Abstract

Summary Two Gram‐negative, plant growth‐promoting rhizobacteria (PGPRs), denominated as M12 and M14, were classified by 16S rDNA sequencing as Burkholderia graminis species. Both strains were shown to produce a variety of N‐acyl‐homoserine lactone (AHL) quorum sensing (QS) signalling molecules. The involvement of these molecules in plant growth promotion and the induction of protection against salt stress was examined. AHL production was evaluated in vitro by thin‐layer chromatography using AHL biosensors, and the identity of the AHLs produced was determined by liquid chromatography‐tandem mass spectrometry. The in situ production of AHLs by M12 and M14 in the rhizosphere of Arabidopsis thaliana plants was detected by co‐inoculation with green fluorescent protein‐based biosensor strains and confocal laser scanning microscopy. To determine whether plant growth promotion and protection against salt stress were mediated by QS, these PGPRs were assayed on wild‐type tomato plants, as well as their corresponding transgenics expressing YenI (short‐chain AHL producers) and LasI (long‐chain AHL producers). In wild‐type tomato plants, only M12 promoted plant growth, and this effect disappeared in both transgenic lines. In contrast, M14 did not promote growth in wild‐type tomatoes, but did so in the LasI transgenic line. Resistance to salt stress was induced by M14 in wild‐type tomato, but this effect disappeared in both transgenic lines. The strain M12, however, did not induce salt resistance in wild‐type tomato, but did so in LasI tomato plants. These results reveal that AHL QS signalling molecules mediate the ability of both PGPR strains M12 and M14 to promote plant growth and to induce protection against salt stress.

Commonalities and Differences in Regulation of N -Acyl Homoserine Lactone Quorum Sensing in the Beneficial Plant-Associated Burkholderia Species Cluster

“…It was established that the BraI/R XEN , BraI/R UNA , and BraI/ R KUR systems respond to C 14 -3-oxo-HSL. This is in accordance with previous studies which demonstrated that other members of the cluster, namely, B. phytofirmans (strains PsJN T and RG6-12) and B. graminis (strains M1 and M14), produce C 14 -3-oxo-HSL (7,77). In summary, these results suggest that 3-oxo-C 14 -HSL is the most probable cognate AHL for the BraI/R-like systems in this Burkholderia cluster.…”

Soil Microorganisms Mediating Phosphorus Availability Update on Microbial Phosphorus

“…Quorum sensing plays an important role in regulation of growth and function of various soil bacteria, including symbionts and some pathogens (including Pseudomonas spp.) that are known to inhabit the rhizosphere (Barriuso et al, 2008;Teplitski et al, 2011). However, research concerning how such factors might shape microbial communities and their functionality in processes like P mobilization are unknown.…”

Quorum-Sensing Mechanisms Mediated by Farnesol in Ophiostoma piceae: Effect on Secretion of Sterol Esterase

“…When the QS molecule reaches a threshold concentration, microbes sense the extracellular signal, and the genes controlled by these mechanisms regulate their expression (7,8). This phenomenon was first studied in bacteria (9,10) and much later reported in fungi, particularly in the pathogenic yeast Candida albicans (11,12), where the sesquiterpene alcohol farnesol (1-hydroxy-3,7,11-trimethyl-2,6,10-dodecatriene) was described as the first QS molecule in eukaryotic organisms (11). However, over the years, other molecules, such as aromatic alcohols, tyrosol, dodecanol, ␥-butyrolactone, or ␥-heptalactone, have been identified as mediators of QS processes in these organisms (13)(14)(15)(16)(17)(18)(19).…”