Suchergebnisse

8 pages, 2 figures, 3 tables.-- PMID: 14623382 [PubMed].-- Printed version published Dec 31, 2003. ; In this study, we evaluated the activity of short antimicrobial peptides against different fungal isolates that cause postharvest decay of fresh fruits. The previously identified hexapeptides PAF19, PAF26 and LfcinB4-9 inhibited the in vitro growth of isolates from Penicillium digitatum and P. italicum, and from Alternaria and Geotrichum genera, being no active against Rhizopus, Mucor and Aspergillus. The results extend our previous observations on the specific and distinct activity profiles of PAFs. In addition, peptide activities were compared with that of two fungicides used for citrus fruit preservation, thiabendazol (TBZ) and imazalil (IMZ). We observed a lack of correlation between peptide and fungicide sensitivity among different species. Importantly, P. digitatum and P. italicum isolates resistant to fungicides were susceptible to peptides, and our data suggest that common multiple drug resistance mechanisms are not active against this class of peptides. The in vitro peptide inhibition was correlated with a retard of the decay caused by Penicillium on citrus fruits, and this effect was comparable for both fungicide-resistant and -sensitive isolates. Comparison of PAF26 and TBZ in vitro MIC values and their in vivo effect on citrus decay indicated that PAF26 performed in vivo better than TBZ. ; Belén López-García was recipient of a pre-doctoral fellowship from Generalitat Valenciana (Spain). This work was supported by grant BIO4-CT97-2086 from the European Union. ; Peer reviewed

The identification of chemical compounds that prevent and combat bacterial diseases is fundamental for crop production. Bacterial virulence inhibitors are a promising alternative to classical control treatments, because they have a low environmental impact and are less likely to generate bacterial resistance. The major virulence determinant of most animal and plant bacterial pathogens is the type III secretion system (T3SS). In this work, we screened nine plant extracts and 12 isolated compounds—including molecules effective against human pathogens—for their capacity to inhibit the T3SS of plant pathogens and for their applicability as virulence inhibitors for crop protection. The screen was performed using a luminescent reporter system developed in the model pathogenic bacterium Ralstonia solanacearum. Five synthetic molecules, one natural product and two plant extracts were found to down‐regulate T3SS transcription, most through the inhibition of the regulator hrpB. In addition, for three of the molecules, corresponding to salicylidene acylhydrazide derivatives, the inhibitory effect caused a dramatic decrease in the secretion capacity, which was translated into impaired plant responses. These candidate virulence inhibitors were then tested for their ability to protect plants. We demonstrated that salicylidene acylhydrazides can limit R. solanacearum multiplication in planta and protect tomato plants from bacterial speck caused by Pseudomonas syringae pv. tomato. Our work validates the efficiency of transcription reporters to discover compounds or natural product extracts that can be potentially applied to prevent bacterial plant diseases. ; This work was funded by projects AGL2013‐46898‐R, AGL2016‐78002‐R and RyC 2014‐16158 from the Spanish Ministry of Economy and Competitiveness. We also acknowledge financial support from the 'Severo Ochoa Program for Centres of Excellence in R&D' 2016–2019 (SEV20150533) and the CERCA Program of the Catalan Government (Generalitat de Catalunya), and from COST Action SUSTAIN (FA1208) from the European Union. M.P. received a project collaboration grant (project 307624) from Fundació Bosch i Gimpera (Universitat de Barcelona) and holds an APIF doctoral fellowship from Universitat de Barcelona. R.A.D. and K.D.B. were supported by an Australian Research Council (ARC) Linkage Grant (LP120200339) and ARC Grants (LE0668477 and LE0237908). ; Peer reviewed