INHIBITION ACTION MECHANISM OF ENANTIO-PYOCHELIN ON Xanthomonas citri, CAUSAL AGENT OF CANKER DISEASE IN LEMON

MICHAVILA, GABRIELA; ADLER, CONRADO; CARAM DI SANTO, MARÍA CAROLINA; LAMI, MARÍA JESUS; COSTA GUTIERREZ SB; VINCENT, PAULA; DE CRISTOBAL, RE

Congreso; 50th Annual Meeting Argentine Society for Biochemistry and Molecular Biology; 2014

SAIB

Bacteria able to inhibit Xanthomonas citri subsp citri, causal agent of canker disease in lemon, were isolated fromcitrus leaf surfaces. Our study was focused in one isolate which showed a remarkable inhibition activity. We studiedbiochemical markers associated with growth promotion i.e. siderophore production and synthesis of indole acetic acid(IAA). The strain was characterized as Pseudomonas fluorescens after sequencing its 16S rRNA. The activecompound was purified and identified as enantio-pyochelin (E-Pch). In an attempt to identify the action mechanismof E-Pch, we evaluated the ability of E-Pch to generate reactive oxygen species (ROS) in X. citri subsp. citri and thecorrelation with its inhibitory activity. In fact, we observed increased ROS levels when E-Pch was added. In addition,the reducer agent ascorbic acid, lowered ROS levels and the antibiotic activity, implying that inhibition is probablycaused by oxidative stress. We studied the biofilm formation of P. fluorescens on the surface of lemon leaves.Finally, we assayed the use of E-Pch in a model of canker disease in Limoneira 8A. We observed that E-Pch reducedcanker formation while ascorbic acid addition reversed its effect. Our results showed E-Pch as a promising compoundfor citrus canker biocontrol and demonstrated that its mechanism of action in vivo and in vitro is by ROS increment.