Signalling of Arabidopsis thaliana response to Pieris brassicae eggs shares similarities with PAMP-triggered immunity

Insect egg deposition activates plant defence, but very little is known about signalling events that control this response. In Arabidopsis thaliana, oviposition by Pieris brassicae triggers salicylic acid (SA) accumulation and induces the expression of defence genes. This is similar to the recognition of pathogen-associated molecular patterns (PAMPs), which are involved in PAMP-triggered immunity (PTI). Here, the involvement of known signalling components of PTI in response to oviposition was studied. Treatment with P. brassicae egg extract caused a rapid induction of early PAMP-responsive genes. In addition, expression of the defence gene PR-1 required EDS1, SID2, and, partially, NPR1, thus implicating the SA pathway downstream of egg recognition. PR-1 expression was triggered by a non-polar fraction of egg extract and by an oxidative burst modulated through the antagonistic action of EDS1 and NUDT7, but which did not depend on the NADPH oxidases RBOHD and RBOHF. Searching for receptors of egg-derived elicitors, a receptor-like kinase mutant, lecRK-I.8, was identified which shows a much reduced induction of PR-1 in response to egg extract treatment. These results demonstrate the importance of the SA pathway in response to egg-derived elicitor(s) and unravel intriguing similarities between the detection of insect eggs and PTI in Arabidopsi

Representativeness of EN 1040/13727 Assay Conditions for Evaluating In Vitro the Bactericidal Activity of a Chlorhexidine Digluconate and Benzalkonium Chloride Antiseptic Preparation

The representativeness of the mandatory bacterial strains specified in European standards for in vitro assay of the bactericidal activity of antiseptics was evaluated by testing the activity of an antiseptic combining chlorhexidine digluconate 0.2% and benzalkonium chloride 0.5% against 21 additional bacterial strains, and the positive interaction between these two biocidal agents was assessed. Methods and Results: The bactericidal activity of the antiseptic solution used pure or diluted was assessed according to the European standards EN 1040 and EN 13727. The contact time was 1 min at 20°C. Interfering substances used in the EN 13727 assay were bovine serum albumin and sheep erythrocytes, simulating “dirty” conditions, and hard water. A reduction of colony-forming units by ≥5 log10 was deemed to meet the requirements to conclude bactericidal activity. Under “basic” conditions, the bactericidal activity of the antiseptic was observed against all four mandatory strains specified in the standards as well as against nearly all the additional strains tested, including most of those with acquired antibiotic-resistance. The positive interaction between the two biocidal agents was also confirmed. Under “dirty” conditions, the bactericidal activity of the antiseptic solution was maintained against all the mandatory strains and was reduced against only four of the additional strains tested. Conclusions: With regard to the antiseptic tested and under the experimental conditions described, bactericidal activity evidenced against the mandatory strains appeared to be representative of that manifested against a wide range of the main pathogenic bacteria. Reduced bacterial activity against some of the additional strains tested (e.g. Enterobacteriaceae) was observed under “dirty” conditions. Significance and Impact of the Study: EN 13727 with some experimental adjustments represents an additional appropriate standard that needs to be considered for mucocutaneous antiseptic assessment. However, it may be worth including other specific bacterial strains to those specified in the standard, when evaluating antiseptics intended for use in certain clinical situation

Generation of reactive species by plasma needle in different líquids

Postprint (published version