NTL8 Regulates Trichome Formation in Arabidopsis by Directly Activating R3 MYB Genes TRY and TCL1

Abstract

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 (Arabidopsis thaliana). 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 NTL8 was tagged; thus, the mutant was named ntl8-1 Dominant (ntl8-1D). Recapitulation experiment further confirmed that the phenotype observed in the ntl8-1D mutant was caused by elevated expression of NTL8. Quantitative RT-PCR results showed that the expression level of the single-repeat R3 MYB genes TRIPTYCHON (TRY) and TRICHOMELESS1 (TCL1) was elevated in the ntl8-1D 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 Gal4:GUS by a fused GAL4 DNA-binding domain, NTL8 activated the expression of the reporter gene. Chromatin immunoprecipitation results indicated that TRY and TCL1 are direct targets of NTL8. However, NTL8 did not interact with SQUAMOSA PROMOTER BINDING PROTEIN LIKE9, another transcription factor that regulates the expression of TRY and TCL1, in yeast and plant cells. Taken together, our results suggest that NTL8 negatively regulates trichome formation in Arabidopsis by directly activating the expression of TRY and TCL1.

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“…Plasmid isolation, protoplast isolation, transfection, incubation, and GUS activity assays were performed by following the procedure described previously (Dai et al, ; Tian et al, ; Wang et al, ; Wang, Wang et al, ). Briefly, plasmids of the reporter and effector constructs were isolated by using a GoldHi EndoFree Plasmid Maxi Kit (Kangwei).…”

The TCP4 Transcription Factor Directly Activates TRICHOMELESS1 and 2 and Suppresses Trichome Initiation

“…No upstream regulators of TCL1 and TCL2 were known until recently (Yu et al, 2010;Tian et al, 2017). NTM1 LIKE8, a membrane-associated NAC transcription factor, has been shown to activate TCL1 and TRY directly (Tian et al, 2017).…”

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