Genetic and molecular analysis of trichome development in Arabis alpina

Significance Typically, comparative developmental studies focus on the question whether key genes are conserved over large evolutionary distances. How the gene regulatory network of a whole developmental process evolves is virtually unknown. This requires a functional comparison of homologous processes in species closely related enough to find similarities and distant enough to see functional changes. We approach this question by genetically and molecularly comparing trichome development in Arabidopsis thaliana with that in Arabis alpina . We show which steps are regulated similarly and which are different. A closer analysis of trichome patterning revealed fascinating changes in the gene regulatory network; in particular, the finding that overexpression of one key regulator leads to opposite phenotypes in the two species suggested fundamental changes.