Plant Pathogenic Microbial Communication Affected by Elevated Temperature in Pectobacterium carotovorum subsp. carotovorum

Abstract

Gram-negative plant pathogenic bacteria regulate specific gene expression in a population density-dependent manner by sensing level of Acyl-Homoserine Lactone (HSL) molecules which they produce and liberate to the environment, called Quorum Sensing (QS). The production of virulence factors (extracellular enzyme viz. cellulase, pectinase, etc.) in Pectobacterium carotovorum subsp. carotovorum (Pcc) is under strong regulation of QS. The QS signal molecule, N-(3-oxohexanoyl)-L-Homoserine Lactone (OHHL) was found as the central regulatory system for the virulence factor production in Pcc and is also under strict regulation of external environmental temperature. Under seven different incubation temperatures (24, 26, 28, 30, 33, 35, and 37 °C) in laboratory condition, highest amount of OHHL (804 violacein unit) and highest (79 %) Disease Severity Index (DSI) were measured at 33 °C. The OHHL production kinetics showed accumulation of highest concentration of OHHL at late log phase of the growth but diminution in the concentration occurred during stationary phase onwards to death phase. At higher temperature (35 and 37 °C) exposure, OHHL was not at detectable range. The effect of temperature on virulence factor production is the concomitant effect of HSL production and degradation which justifies less disease severity index in cross-inoculated tomato fruits incubated at 35 and 37 °C. The nondetection of the OHHL in the elevated temperature may because of degradation as these signal molecules are quite sensitive and prone to get degraded under different physical factors. This result provides the rationale behind the highest disease severity up to certain elevated temperature and leaves opportunities for investigation on mutation, co-evolution of superior plant pathogen with more stable HSL signals-mediated pathogenesis under global warming context.

Beneficial Microorganisms for Corals (BMC): Proposed Mechanisms for Coral Health and Resilience

“…For example, Vibrio growth dynamics and competitiveness in coral mucus and tissues has been demonstrated to be linked to QS signaling molecules such as N -acylhomoserine lactones (AHLs) (Henke and Bassler, 2004; Tait et al, 2010; Certner and Vollmer, 2015). These Vibrio- derived QS molecules are also influenced by environmental factors such as temperature (Tait et al, 2010; Saha et al, 2015) with QS mechanisms breaking down under stress conditions that disrupt the associated microbiome. Certner and Vollmer (2015) demonstrated that resident microorganisms can opportunistically cause white band disease in Acropora cervicornis and that this seems to be regulated by a quorum-sensing signaling molecule.…”

Every cloud has a silver lining: how abiotic stresses affect gene expression in plant-pathogen interactions

“…Thus, the upregulation of these loci under high Finally, some studies have reported a negative regulation of virulence under higher temperatures. A recent study (Saha et al, 2015) analyzed the effect of an array of temperatures (18 to 37 °C) on the phytopathogenic bacterium Pectobacterium carotovorum, responsible for bacterial soft rot in a wide range of plant species. The authors identified an optimal temperature (33°C) for the production of the quorum-sensing signal molecule, acyl homoserine lactone, which regulates bacterial population and virulence gene expression.…”

Distribution of Pectobacterium Species Isolated in South Korea and Comparison of Temperature Effects on Pathogenicity

“…The Peh activity of Pcc, Pbr, and Ppo at 37°C was half of that at 28°C, but Pel activity showed no change except for Ppo. It is well known that PCWDEs are controlled by quorum sensing (QS), and the QS signal molecule, N -(3-oxohexanoyl)-lhomoserine lactone, is not detectable at 37°C ( Hasegawa et al, 2005 ; Põllumaa et al, 2012 ; Saha et al, 2015 ). Golanowska et al (2017) showed that Cel activity of Dickeya species was mainly regulated by temperature, but there was a larger effect of species on pectinase and Prt activities.…”