Localization and expression of EDS5H a homologue of the SA transporter EDS5

An important signal transduction pathway in plant defence depends on the accumulation of salicylic acid (SA). SA is produced in chloroplasts and the multidrug and toxin extrusion transporter ENHANCED DISEASE SUSCEPTIBILITY5 (EDS5; At4g39030) is necessary for the accumulation of SA after pathogen and abiotic stress. EDS5 is localized at the chloroplast and functions in transporting SA from the chloroplast to the cytoplasm. EDS5 has a homologue called EDS5H (EDS5 HOMOLOGUE; At2g21340) but its relationship to EDS5 has not been described and its function is not known. Results: EDS5H exhibits about 72 % similarity and 59 % identity to EDS5. In contrast to EDS5 that is induced after pathogen inoculation, EDS5H was constitutively expressed in all green tissues, independently of pathogen infection. Both transporters are located at the envelope of the chloroplast, the compartment of SA biosynthesis. EDS5H is not involved with the accumulation of SA after inoculation with a pathogen or exposure to UV stress. A phylogenetic analysis supports the hypothesis that EDS5H may be an H+/organic acid antiporter like EDS5. Conclusions: The data based on genetic and molecular studies indicate that EDS5H despite its homology to EDS5 does not contribute to pathogen-induced SA accumulation like EDS5. EDS5H most likely transports related substances such as for example phenolic acids, but unlikely SA

Phytoalexin production of lettuce (Lactuca sativa L.) grown in hydroponics and its in vitro inhibitory effect on plant pathogenic fungi

A series of experiments were conducted to investigate phytoalexin production from five varieties of lettuce in hydroponics using abiotic (2.5, 5% CuSO4 ; 0.5, 1% AgNO3 ) and biotic elicitors (non-pathogenic Pythium sp.) at different plant ages. It showed that phytoalexin was successfully induced in tested lettuce grown in hydroponics after elicitation with abiotic elicitors throughout the trial. Phytoalexin showed yellow fluorescent spot under 365 nm UV light with Rf 0.45-0.48 and clear inhibition zone where Aspergillus niger failed to develop on TLC plate. For biotic elicitors, no yellow fluorescent spot on TLC plate was observed from tested lettuce varieties however inhibition zone at Rf 0.9 was detected at 8-9 weeks from red oak, green oak, and red coral. Moreover, crude extract of lettuce elicited with abiotic elicitors possessed in vitro antifungal activity against C. gloeosporioides, C. lunata, F. oxysporum, and P. aphanidermatum probably due to phytoalexin (lettucenin A) in the extract

EDS5, an Essential Component of Salicylic Acid–Dependent Signaling for Disease Resistance in Arabidopsis, Is a Member of the MATE Transporter Family

The eds5 mutant of Arabidopsis (earlier named sid1) was shown previously to accumulate very little salicylic acid and PR-1 transcript after pathogen inoculation and to be hypersusceptible to pathogens. We have isolated EDS5 by positional cloning and show that it encodes a protein with a predicted series of nine to 11 membrane-spanning domains and a coil domain at the N terminus. EDS5 is homologous with members of the MATE (multidrug and toxin extrusion) transporter family. EDS5 expression is very low in unstressed plants and strongly induced by pathogens and UV-C light. The transcript starts to accumulate 2 hr after inoculation of Arabidopsis with an avirulent strain of Pseudomonas syringae or UV-C light exposure, and it stays induced for ∼2 days. EDS5 also is expressed after treatments with salicylic acid, indicating a possible positive feedback regulation. EDS5 expression after infection by certain pathogens as well as after UV-C light exposure depends on the pathogen response proteins EDS1, PAD4, and NDR1, indicating that the signal transduction pathways after UV-C light exposure and pathogen inoculation share common elements

Novel Small Antimicrobial Peptides Extracted from Agricultural Wastes Act against Phytopathogens but Not Rhizobacteria

Nonedible materials such as agricultural wastes can serve as sources of antimicrobial peptides (AMPs) effective against bacterial plant pathogens. In this study, thirteen agricultural samples were collected and their protein hydrolysates obtained using pepsin. Peptides smaller than 3 kDa were purified by reverse-phase chromatography, cation exchange chromatography, and pI-based fractionation and tested for activity against plant pathogenic bacteria at each step. Active peptides were then analyzed for putative mechanisms using nanoLC–MS/MS and the Mascot program. Ultimately, eight candidate peptides originating from bagasse were selected and chemically synthesized for a comparative study of growth inhibition in plant pathogenic bacteria and plant growth-promoting rhizobacteria (PGPRs). Three synthesized peptides exhibited a potent activity against plant pathogenic bacteria while also supporting the growth of PGPRs. Proteomics analysis revealed the peptides PQLAVF (Pro-Gln-Leu-Ala-Val-Phe) and MDRFL (Met-Asp-Arg-Phe-Leu) to act against Xanthomonas oryzae pv. oryzae via membrane-active mechanisms, while peptide VQLMNSL (Val-Gln-Leu-Met-Asn-Ser-Leu) acted against Pectobacterium carotovorum and Agrobacterium rhizogenes through intracellular-active mechanisms. Further study remains necessary to customize peptides by amino acid substitution not only for a higher effective activity against these and other critical pathogens, but also for a higher stability of peptides in critical condition when applied in industrial processes in the future