Cytokinin-mediated trichome initiation in Nicotiana benthamiana upon Agrobacterium tumefaciens infiltration

Infiltration of Agrobacterium tumefaciens in leaves of Nicotiana benthamiana has become a standard method for transient expression in plants. Like many Solanaceae species, N. benthamiana develops on its leaf surface capitate glandular trichomes that produce and secrete acylsugars. We observed that A. tumefaciens strain GV3101 harboring the disarmed Ti plasmid pMP90 induces de novo formation of GTs and increased production of acylsugars when infiltrated in N. benthamiana leaves. In contrast, other strains, such as AGL1 or LBA4404, do not induce GTs. We demonstrate that the presence of the gene coding for the trans -zeatin synthase ( tzs ) present on pMP90 is responsible for the de novo trichome initiation and that infiltration of cytokinins such as trans -zeatin or benzylaminopurine is sufficient to induce GTs, establishing a direct link between cytokinins and trichome initiation. While these results provide an opportunity to better understand the development of GTs, they make us aware that Agrobacterium infiltration has developmental, biochemical and physiological consequences. To avoid or minimize potential interference of Agrobacterium on the outcome of the infiltration experiments, we recommend testing several strains when establishing a transient assay.