Changes in Gene Expression in Canola Roots Induced by ACC-Deaminase-Containing Plant-Growth-Promoting Bacteria

Changes in Gene Expression in Canola Roots Induced by ACC-Deaminase-Containing Plant-Growth-Promoting Bacteria

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The technique of RNA arbitrarily primed-polymerase chain reaction (RAP-PCR) was used to study changes in gene expression over time in canola roots treated with the 1-aminocyclopropane-1-carboxylate (ACC) deaminase-containing plant-growth-promoting bacterium Enterobacter cloacae UW4 and to compare the changes with those in a mutant of E.cloacae UW4 plastic insert in which the ACC deaminase structural gene acdS was replaced by homologous recombination with acdS with an intentional knockout containing a tetracycline resistance gene.Genes that were either up- or down-regulated over a three-day period in canola plants treated with wild-type or mutant bacteria were isolated, cloned, and sequenced; all appeared to have high homology with Arabidopsis thaliana genes.The upregulated genes included a cell division cycle protein 48 homolog and a eukaryotic translation initiation factor 3 subunit 7 gene homolog.

The downregulated genes included one Eye Cream encoding a glycine-rich RNA binding protein with a function in RNA processing or binding during ethylene-induced stress, which is expressed only in roots, and another gene thought to be involved in a defense signaling pathway.All RAP-PCR results were verified using Northern blotting.These data, indicate that roots isolated from canola seeds treated with the ACC deaminase-producing E.cloacae UW4 up-regulate genes involved in cell division and proliferation but down-regulate stress genes.

This data is in agreement with a model in which ACC deaminase-containing plant-growth-promoting bacteria reduce plant stress and induce root elongation and proliferation in plants, largely by lowering ethylene levels.