The shield and achilles heel of a plant, revealed

Why do some bacteria and viruses cause diseases on certain plant species but not on others? To find out, researchers compared two different kinds of Pseudomonas bacteria - those that are able to penetrate the defenses of the small flowering plant, Arabidopsis, and those that are not - and revealed the complex defense strategies of the plant as well as the techniques that some bacteria employ to sneak by such defenses. In the future, these findings may be useful for improving resistance to disease among crop plants. Jun Fan and colleagues identified a natural product of Arabidopsis, known as sulforaphane, which protects against insects and inhibits the growth of some bacteria in the plants. They also identified a group of bacterial genes, known as sax genes, which are required for other bacteria to successfully infect Arabidopsis plants and cause disease. By introducing certain sax genes into bacteria that are not naturally able to infect the plants, the researchers discovered that those bacteria could suddenly overtake Arabidopsis’ defenses. In light of their findings, Fan and colleagues conclude that molecules like sulforaphane limit the plants’ infection by pathogenic Pseudomonas bacteria, but certain sax genes in the bacteria enable some strains to slip by those defenses.

More information:
"Pseudomonas sax Genes Overcome Aliphatic Isothiocyanate-Mediated Non-Host Resistance in Arabidopsis," by J. Fan; C. Crooks; G. Creissen; L. Hill; S. Fairhurst; C. Lamb at John Innes Centre in Norwich, UK; C. Crooks at USDA Forest Products Laboratory in Madison, WI; P. Doerner at University of Edinburgh in Edinburgh, UK.