Transcriptome profiling of trichome-less reveals genes associated with multicellular trichome development in Cucumis sativus.

Trichomes on plants, similar to fine hairs on animal and human bodies, play important roles in plant survival and development. They also represent a useful model for the study of cell differentiation. Although the regulatory gene network of unicellular trichome development in Arabidopsis thaliana has been well studied, the genes that regulate multicellular trichome development remain unclear. We confirmed that Cucumis sativus (cucumber) trichomes are multicellular and unbranched, but identified a spontaneous mutant, trichome-less (tril), which presented a completely glabrous phenotype. We compared the transcriptome profilings of the tril mutant and wild type using the Illumina HiSeq 2000 sequencing technology. A total of 991 genes exhibited differential expression: 518 were up-regulated and 473 were down-regulated. We further identified 62 differentially expressed genes that encoded crucial transcription factors and were subdivided into seven categories: homeodomain, MADS, MYB, and WRKY domains, ethylene-responsive, zinc finger, and other transcription factor genes. We further analyzed the tissue-expression profiles of two candidate genes, GLABRA2-like and ATHB51-like, using qRT-PCR and found that these two genes were specifically expressed in the epidermis and trichomes, respectively. These results and the tril mutant provide useful tools to study the molecular networks associated with multicellular trichome development.