Microbial homoserine lactones (AHLs) are effectors of root morphological changes in barley.

While colonizing the rhizosphere, bacterial intra- and inter-specific communication is accomplished by N-Acyl-homoserine-lactones (AHLs) in a density-dependent manner. Moreover, plants are naturally exposed to AHLs and respond with tissue-specificity. In the present study, we investigated the influence of N-hexanoyl- (C6-HSL), N-octanoyl- (C8-HSL) and N-dodecanoyl-d/l-homoserine lactone (C12-HSL) on growth and root development in barley (Hordeum vulgare L.), and identified initial reactions in root cells after AHL exposures using physiological, staining, and electrophysiological methods. Treatment with short- and long-chain AHLs modulated plant growth and branched root architecture and induced nitric oxide (NO) accumulation in the calyptra and root elongation zone of excised roots in an AHL derivative-independent way. Additionally, C6- and C8-HSL treatments stimulated K+ uptake in root cells only at certain concentrations, whereas all tested concentrations of C12-HSL induced K+ uptake. In further experiments, C8-HSL promoted membrane hyperpolarization in epidermal root cells. Thus, we conclude AHLs promote plant growth and lateral root formation, and cause NO accumulation as an early response to AHLs. Furthermore, the AHL-mediated membrane hyperpolarization is leading to increased K+ uptake of the root tissue.

A highly versatile and easily configurable system for plant electrophysiology.

In this study we present a highly versatile and easily configurable system for measuring plant electrophysiological parameters and ionic flow rates, connected to a computer-controlled highly accurate positioning device. The modular software used allows easy customizable configurations for the measurement of electrophysiological parameters. Both the operational tests and the experiments already performed have been fully successful and rendered a low noise and highly stable signal. Assembly, programming and configuration examples are discussed. The system is a powerful technique that not only gives precise measuring of plant electrophysiological status, but also allows easy development of ad hoc configurations that are not constrained to plant studies. •We developed a highly modular system for electrophysiology measurements that can be used either in organs or cells and performs either steady or dynamic intra- and extracellular measurements that takes advantage of the easiness of visual object-oriented programming.•High precision accuracy in data acquisition under electrical noisy environments that allows it to run even in a laboratory close to electrical equipment that produce electrical noise.•The system makes an improvement of the currently used systems for monitoring and controlling high precision measurements and micromanipulation systems providing an open and customizable environment for multiple experimental needs.

Adaptation of AmtR-controlled gene expression by modulation of AmtR binding activity in Corynebacterium glutamicum.

In corynebacteria, nitrogen regulation is controlled by the TetR family protein AmtR, which was extensively studied in the last years. In frame of these studies a number of AmtR binding sites were identified and characterized and it became obvious that for distinct genes the number and sequences of these sites varied significantly. In this study, the influence of numbers and alterations of AmtR binding sites were addressed by in vivo and in vitro studies. It can be concluded that in general a single highly conserved AmtR site is sufficient for stringent regulation and that non-conserved binding sites have a very limited influence, despite the fact that binding of AmtR was shown for several of these sites, e.g. upstream of amtA, amtB and gdh. Furthermore, the reason for and consequences of the lack of AmtR autoregulation were addressed in vivo. The introduction of a spacing nucleotide between the two conserved half sites of the AmtR binding box alone is sufficient to restore AmtR autoregulation. The main differences observed between wild type and an AmtR autoregulation strain were a slightly enhanced background of transcription of AmtR-controlled genes and a slightly slower response to nitrogen limitation.