The coronafacoyl phytotoxins: structure, biosynthesis, regulation and biological activities

Phytotoxins are secondary metabolitesthat contribute to the development and/or severity ofdiseases caused by various plant pathogenic microorganisms.The coronafacoyl phytotoxins are an importantfamily of plant toxins that are known or suspectedto be produced by several phylogenetically distinctplant pathogenic bacteria, including the gammaproteobacteriumPseudomonas syringae and the actinobacteriumStreptomyces scabies. At least sevendifferent family members have been identified, ofwhich coronatine was the first to be described and isthe best-characterized. Though nonessential for diseasedevelopment, coronafacoyl phytotoxins appear toenhance the severity of disease symptoms induced bypathogenic microbes during host infection. In addition,the identification of coronafacoyl phytotoxinbiosynthetic genes in organisms not known to be plantpathogens suggests that these metabolites may haveadditional roles other than as virulence factors. Thisreview focuses on our current understanding of thestructures, biosynthesis, regulation, biological activitiesand evolution of coronafacoyl phytotoxins as wellas the different methods that are used to detect thesemetabolites and the organisms that produce them.Keywords Phytotoxins Secondary metabolites Coronatine N-Coronafacoyl-L-isoleucine Pseudomonas Streptomyce