NTL8 Regulates Trichome Formation in Arabidopsis by Directly Activating R3 MYB Genes and .

The NAM, ATAF1/2, and CUC (NAC) are plant-specific transcription factors that regulate multiple aspects of plant growth and development and plant response to environmental stimuli. We report here the identification of NTM1-LIKE8 (NTL8), a membrane-associated NAC transcription factor, as a novel regulator of trichome formation in Arabidopsis (). From an activation-tagged Arabidopsis population, we identified a dominant, gain-of-function mutant with glabrous inflorescence stem. By using plasmid rescue and RT-PCR analyses, we found that was tagged; thus, the mutant was named (). Recapitulation experiment further confirmed that the phenotype observed in the mutant was caused by elevated expression of Quantitative RT-PCR results showed that the expression level of the single-repeat R3 MYB genes () and () was elevated in the mutant. Genetic analyses demonstrated that NTL8 acts upstream of TRY and TCL1 in the regulation of trichome formation. When recruited to the promoter region of the reporter gene by a fused GAL4 DNA-binding domain, NTL8 activated the expression of the reporter gene. Chromatin immunoprecipitation results indicated that and are direct targets of NTL8. However, NTL8 did not interact with SQUAMOSA PROMOTER BINDING PROTEIN LIKE9, another transcription factor that regulates the expression of and , in yeast and plant cells. Taken together, our results suggest that NTL8 negatively regulates trichome formation in Arabidopsis by directly activating the expression of and .