Virulent Rhodococcus fascians Produce Unique Methylated Cytokinins.

Paula Elizabeth Jameson

doi:10.3390/plants8120582

Abstract

Some strains of Rhodococcus fascians exist only as epiphytes on the plant surface whereas others can become endophytic and cause various abnormalities including the release of multiple buds and reduced root growth. The abnormalities reflect the action of cytokinin. The strains that can become endophytic harbour a linear plasmid that carries cytokinin biosynthesis, activation and destruction genes. However, both epiphytic and endophytic forms can release cytokinin into culture, affect cytokinin metabolism within inoculated plants and enhance the expression of sugar and amino acid transporters and cell wall invertases, but only the endophytic form markedly affects the morphology of the plant. A unique methylated cytokinin, dimethylated N6-(∆2-isopentenyl)adenine (2-MeiP), operating in a high sugar environment, is the likely causative factor of the severe morphological abnormalities observed when plants are inoculated with R. fascians strains carrying the linear plasmid.

Highlights

Unique methylated cytokinins account for the morphological abnormalities induced by virulent strains of Rhodococcus fascians
Cytokinin biosynthesis usually involves the attachment of an isoprenoid side chain to a molecule of either AMP or ADP/ATP by an isopentenyl transferase (IPT)
We have shown that both virulent and avirulent strains of R. fascians can produce the cytokinins implicated the ‘Trick-with-the-Cytokinin-Mix’

Summary

Introduction

Unique methylated cytokinins account for the morphological abnormalities induced by virulent strains of Rhodococcus fascians. Both avirulent (epiphytic) as well as virulent strains of R. fascians have been shown to extrude multiple different cytokinins into culture, most of which can, be derived from tRNA Multiple cytokinins can be extracted from plants inoculated with both virulent and avirulent strains e.g., [12,13,14,15].

Results

Conclusion