An operon for production of bioactive gibberellin A4 phytohormone with wide distribution in the bacterial rice leaf streak pathogen Xanthomonas oryzae pv. oryzicola

Date
2017-05-01
Authors
Nagel, Raimund
Turrini, Paula
Nett, Ryan
Leach, Jan
Verdier, Valérie
Van Sluys, Marie-Anne
Peters, Reuben
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Abstract

• Phytopathogens have developed elaborate mechanisms to attenuate the defense response of their host plants, including convergent evolution of complex pathways for production of the gibberellin (GA) phytohormones, which were actually first isolated from the rice fungal pathogen Gibberella fujikuroi. The rice bacterial pathogen Xanthomonas oryzae pv. oryzicola (Xoc) has been demonstrated to contain a biosynthetic operon with cyclases capable of producing the universal GA precursor ent-kaurene. Genetic (knock-out) studies indicate that the derived diterpenoid serves as a virulence factor for this rice leaf streak pathogen, serving to reduce the jasmonic acid (JA) mediated defense response.

• Here the function of the remaining genes in the Xoc operon are elucidated and the distribution of the operon in X. oryzae investigated in over 100 isolates.

• The Xoc operon leads to production of the bioactive GA4, an additional step beyond production of the penultimate precursor GA9 mediated by the homologous operons recently characterized from rhizobia. Moreover, this GA biosynthetic operon was found to be widespread in Xoc (>90%), but absent in the other major oryzae pathovar.

• These results indicate selective pressure for production of GA4 in the distinct lifestyle of Xoc, and the importance of GA to both fungal and bacterial pathogens of rice.

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This is the peer reviewed version of the following article: Nagel, Raimund, Paula CG Turrini, Ryan S. Nett, Jan E. Leach, Valérie Verdier, Marie‐Anne Van Sluys, and Reuben J. Peters. "An operon for production of bioactive gibberellin A4 phytohormone with wide distribution in the bacterial rice leaf streak pathogen Xanthomonas oryzae pv. oryzicola." New Phytologist 214, no. 3 (2017): 1260-1266, which has been published in final form at doi: 10.1111/nph.14441. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.

Keywords
biogeographical distribution, cytochromes P450, gibberellin biosynthesis, plant–microbe interactions, virulence factor
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