Hormone-mediated promotion of trichome initiation in plants is conserved but utilizes species- and trichome-specific regulatory mechanisms.

Plant trichome initiation is steered by diverse developmental and environmental cues, through molecular mechanisms that remain elusive in most plant species. Using a robust experimental method to investigate the molecular mechanisms by which phytohormones modulate leaf trichome formation, we verified the effect of jasmonates, cytokinins and gibberellins in Arabidopsis (). All three phytohormones promoted Arabidopsis trichome initiation, but caused divergent effects on trichome maturation and other leaf parameters. Molecular analysis indicated that the phytohormones mediated trichome initiation by the transcriptional regulation of the components of the TRANSPARENT TESTA GLABRA1 (TTG1) activator/inhibitor complex. In this addendum, we additionally studied the effects of jasmonates, cytokinins and gibberellins on leaf trichome formation in a representative set of plant species, spanning the angiosperm lineage and covering different trichome types. We found that the general ability of the three phytohormones to impinge on trichome initiation is conserved across angiosperms, but that within a particular plant species distinct regulatory networks might be activated to steer the formation of the various trichome types.