Agrobacterium tumefaciens-based transient assays have become a common tool
in researches regarding protein localization and gene expression in cells.
However, the cellular organization and organelle morphology in
Agrobacterium-infiltrated cells has not been examined in detail. The
objective of this study was to characterize the effect of Agrobacterium
tumefaciens-based transient assay on the cell from short-term bacterial
infestation as well as to identify the factor responsible for these changes.

The impact of GV3101 infiltration on chloroplast behaviour and morphology in
Nicotiana benthamiana was evaluated. Our experiments confirmed that GV3101
consistently induces stromules or 'stroma-filled-tubules' and alters plastid
position relative to the nucleus. These were the result of a
strain-dependent secretion of cytokinin and its accumulation in the plant
tissue. The production of the hormone by the bacteria was found to be
dependent on the presence of a trans-zeatin synthase gene (tzs) located on
the Ti plasmid of GV3101. Bacteria-derived cytokinins also affected both
soluble sugar level and starch accumulation.

The impact of the bacteria can be minimized by utilizing Agrobacterium
strains without the tzs gene, however, the alterations can not be completely
avoided using this strategy.

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