Study of the crtZ in Pseudomonas fluorescens isolated from grape roots as related to bacterial synthesis of abscisic acid

JOHANA DOMINGUEZ; SANDRA GARCIA LAMAPZONA; ANA C. COHEN; M. VICTORIA SALOMON; PATRICIA PICCOLI

Tucuman

Congreso; VII Congreso Argentino de Microbiologia General. SAMIGE DEL BICENTENARIO; 2011

Sociedad Argentina de Microbiologia General

Plant growth-promoting rhizobacteria (PGPR) colonize the root system of several plants with the effect of increasing yield. Among the mechanisms proposed to explain such beneficial effect is the production of phytohormones by the bacteria, including abscisic acid (ABA). In this regard Pseudomonas fluorescens has received particular attention. We have previously isolated P. fluorescens from roots of Vitis vinifera (cv. Malbec L.) and demonstrated that it produces ABA in chemically-defined medium. The aim of this work was to study if the crtZ gene, which encodes a crucial enzyme in the biosynthesis of zeaxanthin in bacteria, is present in P. fluorescens. The crtZ gene encodes the enzyme â carotene hydroxylase, an oxidoreductase involved in the biosynthesis of zeaxanthin from â carotene hydroxylation. In plants, zeaxanthin is a key intermediate in the biosynthesis of ABA. Specific primers were designed from the crtZ gene sequence presents in Pseudomonas putida KT 2440. The expected gene was amplified by PCR and then cloned into competent cells. Plasmidic DNA was extracted and sequenced. Homology searches were done using the basic local alignment Search Tool BLAST program showing 98% homology with the crtZ gene found in Pseudomonas putida KT 2440. This result shows that crtZ gene is present in Pseudomonas fluorescens, which strongly suggests that the ABA biosynthetic pathway in bacteria is via 1-deoxy-D-xylulose-5-phosphate (DXP) by carotenoid breakdown, as it happens in plastids of plants.