engleski

Effect of auxins on plant pathogenic phytoplasmas and phytoplasma-infected host

Broad scientific evidence exists on the effects of auxins in higher plants and on the role of indole-3-acetic acid in plant-microbe communication. However, recent research reveals possible new application of these plant growth regulators in treatment of phytoplasma-infected plants. Phytoplasmas are wall-less, non-helical, endocellular prokaryotes that inhabit plant phloem and insects and cause numerous economically important diseases. In attempts to eliminate these pathogens from infected plants various treatments have been tested in the last decades. Because these pathogens have reduced genomes and are therefore presumably more dependent on the metabolism of their hosts than are other plant pathogens, an idea arose that by changing auxin levels, an environment unfavorable for phytoplasma growth could be generated inside the host. Indeed, addition of indole-3-butyric acid to the medium on which phytoplasma-infected periwinkle shoots were grown in vitro caused recovery of the host and elimination of two ‘Candidatus Phytoplasma’ species. Other ‘Ca. P.’ species tested remained in the periwinkle shoots in the high titer despite the obvious IBA-induced recovery of the host. Changes in global host genome methylation were confirmed in cases when auxin-dependent host recovery was associated with the elimination of phytoplasma, suggesting that IBA-induced epigenetic changes could have caused this desirable effect. The results imply that the effect of IBA on phytoplasma was most probably indirect - changes in host metabolism affected growth and survival of ‘Candidatus Phytoplasma asteris’ and ‘Candidatus Phytoplasma pruni’ in infected host Catharanthus roseus (L.) G. Don. Although IBA-treatment induced recovery of phytoplasma-infected periwinkle and caused elimination of two ‘Ca. P.’ species, its effectiveness in other phytoplasma-infected plants is yet to be tested.

IAA, IBA, phytoplasma

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