Azospirillum brasilense FP2 modulates respiratory burst oxidase gene expression in maize seedlings

Abstract

Azospirillum brasilense is free-living gram-negative bacteria isolated from the rhizosphere of grasses. The plant growth promoting rhizobacteria, such as A. brasilense, can promote plant growth through biological nitrogen fixation and phytohormones production. Our aim was to evaluate the expression of several maize genes involved in stress response of maize (Pioneer 30F53 variety) after inoculation with A. brasilense strain FP2. Samples were collected 1, 4, 7 and 10 days after inoculation (DAI). Significant increase of the transcript level was observed for Auxin transporter-like protein 1 (Zmaux1), Respiratory burst oxidase protein (ZmrbohA and ZmrbohB), MAP kinase 5 (Zmmpk5), Gibberellin 20 oxidase 4 (Zmga20ox4) and Ent-kaurene oxidase (Zmko1) when comparing inoculated to non-inoculated samples. For root samples, increasing transcripts levels for Zmmpk5 gene were observed from 1 to 7 DAI, and a decrease at 10 DAI in inoculated samples compared to non-inoculated. The modulation of gene expression observed for genes involved in the oxidative burst (ZmrbohA and ZmrbohB) and for the signal transduction chain (Zmmpk5), indicates that the plant respond to the presence of the bacterium.