Plant trichomes are special structures that originate from epidermal outgrowths. Trichomes play an important role in plant defense against pests and diseases, and possess economic and medicinal values. Study on molecular mechanism of plant trichomes will contribute to the molecular design breeding and genetic improvement of crops. In recent years, the regulation mechanism of trichome development has been basically clarified in the model plant Arabidopsis thaliana, while great progresses are also found in other plant species. In this review, we focus on the developmental regulation of trichome formation from gene and phytohormones levels in Arabidopsis and cotton (with unicellular trichomes), as well as in tomato and Artemisia annua (with multicellular trichomes). The research progress associated with trichomes is also introduced in other typical monocotyledons and dicotyledons. Finally, the research and application of plant trichomes are prospected.
Arabidopsis/genetics* ; Gene Expression Regulation, Plant ; Gossypium/genetics* ; Lycopersicon esculentum ; Plant Growth Regulators/metabolism* ; Trichomes/genetics*

Hd-Zip, a unique transcription factor in plant kingdom, influences the growth, development, and secondary metabolism of plants. Hd-zip Ⅳ is thought to play an important role in trichome development of Schizonepeta tenuifolia. This study aims to explore the functions of StHD1 and StHD8 in Hd-zip Ⅳ subfamily in peltate glandular trichome development. To be specific, the expression patterns of the two genes and interaction between the proteins encoded by them were analyzed based on transcriptome sequencing and two-hybrid screening. The subcellular localization was performed and functions of the genes were verified in tobacco and S. tenuifolia. The results showed that StHD1 and StHD8 had high similarity to HD-Zip Ⅳ proteins of other plants and they all had the characteristic conserved domains of HD-Zip Ⅳ subfamily. They were located in the nucleus. The two genes mainly expressed in young tissues and spikes, and StHD1 and StHD8 proteins interacted with each other. The density and length of glandular trichomes increased significantly in tobacco plants with the overexpression of StHD1 and StHD8. Inhibiting the expression of StHD1 and StHD8 by VIGS(virus-induced gene silencing) in S. tenuifolia resulted in the reduction in the density of peltate glandular trichomes, the expression of key genes related to mono-terpene synthesis, and the relative content of limonene and pulegone, the main components of monoterpene. These results suggested that StHD1 and StHD8 of S. tenuifolia formed a complex to regulate glandular trichomes and affect the biosynthesis of monoterpenes.
Trichomes/metabolism* ; Lamiaceae/genetics* ; Tobacco/genetics* ; Monoterpenes/metabolism* ; Cloning, Molecular ; Plant Proteins/metabolism* ; Gene Expression Regulation, Plant