Both pathogenic and epiphytic organisms obtain nutrients from host plants. Dhandapani et al. show the differential impact of an epiphytic (avirulent) strain and a pathogenic strain of the cytokinin-producing bacterium, Rhodococcus fascians on source/sink relationships within pea cotyledons during and following germination.
Both strains commandeered resources from the cotyledon, but only the pathogenic strain markedly impacted development. The authors suggest that the interaction between cytokinins, cell-wall invertases (CWINVs) and SWEET genes may lead to the loss of apical dominance and the appearance of multiple shoots that characterise infection by virulent R. fascians.
Dhandapani, P., Song, J., Novak, O., & Jameson, P. E. (2016). Infection by Rhodococcus fascians maintains cotyledons as a sink tissue for the pathogen. Annals of Botany, mcw202. https://doi.org/10.1093/aob/mcw202