The Genetic Wiring of Plant Trichomes: From Initiation to Fate Specification

Plant trichomes are not just simple hairs but metabolic powerhouses shaped by complex genetic programs. While the MYB‐bHLH‐WD40 module is well studied in Arabidopsis, recent findings reveal that HD‐Zip IV transcription factors drive multicellular and glandular trichome development through dose‐dependent mechanisms. This review explores how diverse regulatory networks control trichome initiation, fate, and function—offering new paths for engineering plant defense and natural product synthesis. Abstract Plant trichomes serve as essential physical barriers and highly specialized metabolic powerhouses, producing a vast array of ecologically and economically significant compounds. While the MYB‐bHLH‐WD40 (MBW) complex governing unicellular trichome development in Arabidopsis thaliana is well‐established, accumulating evidence suggests the existence of distinct mechanisms in regulating multicellular trichomes in other plant species. This review summarizes recent breakthroughs revealing significant divergence in species forming multicellular and glandular trichomes. The molecular networks orchestrating trichome fate determination and morphogenesis are focused, emphasizing the pivotal role and dose‐dependent mechanisms of homeodomain‐leucine zipper class IV (HD‐Zip IV) transcription factors. This review highlights the complexity and species specificity of trichome developmental programming. Understanding these underlying developmental blueprints is fundamental for elucidating how plants build these metabolic powerhouses and holds promise for future applications in enhancing plant defense and optimizing natural product biosynthesis. Plant trichomes are not just simple hairs but metabolic powerhouses shaped by complex genetic programs. While the MYB-bHLH-WD40 module is well studied in Arabidopsis, recent findings reveal that HD-Zip IV transcription factors drive multicellular and glandular trichome development through dose-dependent mechanisms. This review explores how diverse regulatory networks control trichome initiation, fate, and function—offering new paths for engineering plant defense and natural product synthesis. Abstract Plant trichomes serve as essential physical barriers and highly specialized metabolic powerhouses, producing a vast array of ecologically and economically significant compounds. While the MYB-bHLH-WD40 (MBW) complex governing unicellular trichome development in Arabidopsis thaliana is well-established, accumulating evidence suggests the existence of distinct mechanisms in regulating multicellular trichomes in other plant species. This review summarizes recent breakthroughs revealing significant divergence in species forming multicellular and glandular trichomes. The molecular networks orchestrating trichome fate determination and morphogenesis are focused, emphasizing the pivotal role and dose-dependent mechanisms of homeodomain-leucine zipper class IV (HD-Zip IV) transcription factors. This review highlights the complexity and species specificity of trichome developmental programming. Understanding these underlying developmental blueprints is fundamental for elucidating how plants build these metabolic powerhouses and holds promise for future applications in enhancing plant defense and optimizing natural product biosynthesis. Advanced Science, EarlyView.