Metabolites Secreted by a Plant-Growth-Promoting Pantoea agglomerans Strain Improved Rooting of Pyrus communis L. cv Dar Gazi Cuttings

Abstract

Strains belonging to Pantoea agglomerans species are known for their ability to produce metabolites that can act in synergy with auxins to induce the adventitious root (AR) formation. The latter is critically important in the agamic propagation of several woody species, including pear ( Pyrus communis L.), playing a considerable role in the commercial nursery farms including those using micropropagation techniques. When grown on a medium amended with tryptophan, the plant-growth-promoting (PGP) strain P. agglomerans C1 produces a cocktail of auxin and auxin-like molecules that can be utilized as biostimulants to improve the rooting of vegetable ( Solanum lycopersicum L.) and woody crop species ( Prunus rootstock GF/677 and hazelnut). In this study, we evaluated the morphological and molecular responses induced by strain C1 exometabolites in microcuttings of P. communis L. cv Dar Gazi and the potential benefits arising from their application. Results showed that exometabolites by P. agglomerans C1 induced a direct and earlier emergence of roots from stem tissues and determined modifications of root morphological parameters and root architecture compared to plants treated with the synthetic hormone indole-3-butyric acid (IBA). Transcription analysis revealed differences in the temporal expression pattern of ARF17 gene when IBA and C1 exometabolites were used alone, while together they also determined changes in the expression pattern of other key auxin-regulated plant genes. These results suggest that the phenotypic and molecular changes triggered by P. agglomerans C1 are dependent on different stimulatory and inhibitory effects that auxin-like molecules and other metabolites secreted by this strain have on the gene regulatory network of the plant. This evidence supports the hypothesis that the strategies used to harness the metabolic potential of PGP bacteria are key factors in obtaining novel biostimulants for sustainable agriculture. Our results demonstrate that metabolites secreted by strain C1 can be successfully used to increase the efficiency of micropropagation of pear through tissue culture techniques.

Small RNA and Degradome Sequencing Reveal Important MicroRNA Function in Nicotiana tabacum Response to Bemisia tabaci

“…The effect of this miRNA is consistent with the above miRNAs. PC-5p-194313_25 targeted to auxin-induced protein genes that are involved in the auxin signaling pathway [ 60 ]. We speculated that PC-5p-194313_25 and miRNA160 had similar functions, that is, induced by whitefly infestation and enhanced resistance via the inhibiting auxin signaling pathway.…”

The Microbiome of the ‘Williams’ Pear Variety Grown in the Organic Orchard and Antifungal Activity by the Autochthonous Bacterial and Yeast Isolates

“…was also observed [ 20 ]. Recently, Luziatelli et al [ 37 ] showed the beneficial effects of the metabolites secreted by a plant-growth-promoting Pantoea agglomerans on the Pyrus communis variety ‘Dar Gazi’ by improving its rooting. Considering the effect of the fruit phenophase on the composition of culturable microbiota, Janisiewicz et al [ 38 ] also observed a decline in the abundance of Pseudomonas spp.…”

β-Cyclocitral, a Master Regulator of Multiple Stress-Responsive Genes in Solanum lycopersicum L. Plants

“…The trend of gene expression without removing the transcriptional repressor is also evident in AUX signaling. βCC treatment increases the accumulation of AUX responsive proteins, namely small auxin upregulated RNA (SAUR 71) and AUX-induced proteins 15-like (homologous to the SAUR7 gene from A. thaliana) [56], without altering the expression of AUX/IAA proteins, a repressor of early auxin response genes' expression [57]. It is known that in plants, the ubiquitin system is an integral part of hormonal signal transduction.…”