Complete genome sequence of Pseudomonas fluorescens strain PICF7, an indigenous root endophyte from olive (Olea europaea L.) and effective biocontrol agent against Verticillium dahliae

Abstract

Pseudomonas fluorescens strain PICF7 is a native endophyte of olive roots. Previous studies have shown this motile, Gram-negative, non-sporulating bacterium is an effective biocontrol agent against the soil-borne fungus Verticillium dahliae, the causal agent of one of the most devastating diseases for olive (Olea europaea L.) cultivation. Here, we announce and describe the complete genome sequence of Pseudomonas fluorescens strain PICF7 consisting of a circular chromosome of 6,136,735 bp that encodes 5,567 protein-coding genes and 88 RNA-only encoding genes. Genome analysis revealed genes predicting factors such as secretion systems, siderophores, detoxifying compounds or volatile components. Further analysis of the genome sequence of PICF7 will help in gaining insights into biocontrol and endophytism.

Keywords: Biocontrol; Detoxification systems; Endophyte; Olive; Pseudomonas fluorescens; Siderophores; Verticillium wilt.

Figure 1

Image of P. fluorescens PICF7 cells using confocal laser scanning (Left) and phase-contrast (Centre) microscopy (CLSM and PCM, respectively) and the appearance of colony morphology after 24 h growing on KB agar medium at 28°C (Right). CLSM image was obtained using a PICF7 derivative carrying a plasmid with an enhanced green fluorescent protein (EGFP) [5].

Figure 2

Phylogenetic tree highlighting the position of P. fluorescens strain PICF7 relative to its closest Pseudomonas strains for which complete genomes are available.P. entomophila strain L48 was used as an outgroup. For the construction of the tree, five protein-coding house-keeping genes were first aligned, namely: argF, atpA, nusA, pyrH and rpoH. Then, Maximum Likelihood method based on the JTT (Jones-Taylor-Thornton) matrix-based model [29] was used. The percentage of trees in which the associated taxa clustered in the bootstrap test (1000 replicates) is shown next to the branches [30].

Figure 3

Graphical map of the chromosome. From outside to the centre: genes on forward strand (coloured by COG categories), genes on reverse strand (coloured by COG categories), RNA genes: tRNAs - blue, rRNAs – pink, G + C in relation to the mean G + C in 2 kb windows and trinucleotide distribution in 2 kb windows. The latter was defined as the χ2 statistic on the difference between the trinucleotide composition of 2 kb windows and that of the whole chromosome.