Study of the molecular mechanisms involved in the growth inhibition of Acidovorax avenae subsp. avenae by bacterial volatile organic compounds

Abstract

Sugarcane (cane) production is one of the most important sectors of the Brazilian economy, representing 2% of the national Gross Domestic Product (GDP). Currently, Brazil is the world's largest producer of this crop and, despite its high productivity, sugarcane cultivation is still severely affected by biotic limiting factors, such as insects and phytopathogenic microorganisms, which can be responsible for great economic losses. In order to change this scenario through sustainable agricultural practices, this study aims to contribute to the use of microorganisms in the biocontrol of plant diseases, focusing on volatile organic bacterial compounds (VOCs), as growth inhibitors of phytopathogens. VOCs are small metabolites (usually with less than 15 carbon atoms) produced by microorganisms and which easily volatilize at room temperature, being important signaling molecules that can permeate through soil, water and air. The disease highlighted in this study is the red stripe, caused by the bacterium Acidovorax avenae subsp. avenae, characterized by the appearance of red, thin and long stripes on the leaves and by the rot of the cane stalk. This phytobacterium can also cause serious damage in other crops such as rice, corn, oats and millet, being relevant worldwide. Previously, our group has identified two bacteria capable of inhibiting the growth of A. avenae by about 80% through VOCs, and the set of these metabolites produced by both isolates was analyzed. Thus, the objective of this study is to identify which volatiles produced by the isolates are responsible for inhibiting the growth of A. avenae, by evaluating the antimicrobial activity of synthetic VOCs. In addition, the objective is to understand the molecular mechanisms involved in this inhibition by analyzing the expression of genes related to virulence and pathogenicity of A. avenae in the presence and absence of the VOCs by real-time PCR. Finally, we propose to determine whether the inhibition observed in vitro also occurs in vivo, conducting co-culture assays of antagonistic bacteria in sugar cane and rice seedlings infected with A. avenae. This study seeks to characterize new bioactive molecules as well as to understand how they work, enabling, in the future, the development of bioproducts aiming at a more sustainable agriculture.