Zinc Finger Protein 6 (ZFP6) regulates the trichome initiation by integrating GA and Cytokinin signalling in Arabidopsis thaliana
Zhongjing Zhou, Lijun An, Lili Sun, Yongqin, Zhao, An Yan, Xiaofang Meng and Yinbo Gan* 

Department of Agronomy, College of Agriculture and Biotechnology, Zhejiang University, 866 Yuhangtang Rd, Hangzhou, 310058, China 

Abstract
C2H2 zinc finger protein plays an important role in controlling shoot maturation and epidermal cell fate in Arabidopsis. Our previous studies have shown that the GLABROUS INFLORESCENCE STEMS (GIS) and ZINC FINGER PROTEIN 5 (ZFP5) play an important role in controlling trichome cell initiation through gibberellin (GA) signaling and GIS2 and ZFP8 control trichome cell development by integrating gibberellin and cytokinin signaling in Arabidopsis. Here, we identify a novel C2H2 zinc finger protein ZINC FINGER PROTEIN 6 (ZFP6) which plays a key role in regulating trichome development in Arabidopsis. Overexpression of ZFP6 results in ectopic trichomes on carpels and other inflorescence organs. ZFP6 loss-of-function mutants exhibit reduced number of trichomes in sepals of flowers, cauline leaves, lateral branch and main inflorescence stems in comparison to wild-type plants. We further report that ZFP6 and ZFP5 mediate the regulation of trichome initiation by integrating gibberellin and cytokinin signaling. Histochemical staining for GUS activity in pZFP6::GUS transgenic plants reveals ZFP6 is expressed specifically in the trichomes of inflorescence organs.  The molecular and genetic analyses suggest that ZFP6 functions upstream of GIS, GIS2, ZFP8, ZFP5, and key trichome initiation regulators GL1 and GL3. These findings provide new insights into the molecular mechanism of plant hormone control of epidermal trichome patterning through C2H2 transcriptional factors.