title: ARGONAUTE10 and ARGONAUTE1 regulate the termination of floral stem cells through two microRNAs in Arabidopsis.
abstract: Stem cells are crucial in morphogenesis in plants and animals. Much is known about the mechanisms that maintain stem cell fates or trigger their terminal differentiation. However, little is known about how developmental time impacts stem cell fates. Using Arabidopsis floral stem cells as a model, we show that stem cells can undergo precise temporal regulation governed by mechanisms that are distinct from, but integrated with, those that specify cell fates. We show that two microRNAs, miR172 and miR165/166, through targeting APETALA2 and type III homeodomain-leucine zipper (HD-Zip) genes, respectively, regulate the temporal program of floral stem cells. In particular, we reveal a role of the type III HD-Zip genes, previously known to specify lateral organ polarity, in stem cell termination. Both reduction in HD-Zip expression by over-expression of miR165/166 and mis-expression of HD-Zip genes by rendering them resistant to miR165/166 lead to prolonged floral stem cell activity, indicating that the expression of HD-Zip genes needs to be precisely controlled to achieve floral stem cell termination. We also show that both the ubiquitously expressed ARGONAUTE1 (AGO1) gene and its homolog AGO10, which exhibits highly restricted spatial expression patterns, are required to maintain the correct temporal program of floral stem cells. We provide evidence that AGO10, like AGO1, associates with miR172 and miR165/166 in vivo and exhibits "slicer" activity in vitro. Despite the common biological functions and similar biochemical activities, AGO1 and AGO10 exert different effects on miR165/166 in vivo. This work establishes a network of microRNAs and transcription factors governing the temporal program of floral stem cells and sheds light on the relationships among different AGO genes, which tend to exist in gene families in multicellular organisms.
authors.affiliation: Department of Botany and Plant Sciences, Institute of Integrative Genome Biology, University of California Riverside, Riverside, California, United States of America.
authors.forename: Lijuan
authors.initials: L
authors.lastname: Ji
authors.forename: Xigang
authors.initials: X
authors.lastname: Liu
authors.forename: Jun
authors.initials: J
authors.lastname: Yan
authors.forename: Wenming
authors.initials: W
authors.lastname: Wang
authors.forename: Rae Eden
authors.initials: RE
authors.lastname: Yumul
authors.forename: Yun Ju
authors.initials: YJ
authors.lastname: Kim
authors.forename: Thanh Theresa
authors.initials: TT
authors.lastname: Dinh
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
authors.forename: Xia
authors.initials: X
authors.lastname: Cui
authors.forename: Binglian
authors.initials: B
authors.lastname: Zheng
authors.forename: Manu
authors.initials: M
authors.lastname: Agarwal
authors.forename: Chunyan
authors.initials: C
authors.lastname: Liu
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Cao
authors.forename: Guiliang
authors.initials: G
authors.lastname: Tang
authors.forename: Xuemei
authors.initials: X
authors.lastname: Chen
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000254:growth & development*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000502:physiology*; D060565:Argonaute Proteins; D035264:Flowers / Q000166:cytology / Q000235:genetics / Q000254:growth & development*; D018506:Gene Expression Regulation, Plant; D018398:Homeodomain Proteins / Q000235:genetics / Q000502:physiology; D018519:Meristem / Q000235:genetics / Q000502:physiology; D035683:MicroRNAs / Q000235:genetics*; D009687:Nuclear Proteins / Q000235:genetics / Q000502:physiology; D013234:Stem Cells / Q000166:cytology / Q000502:physiology
chemical_list: D029681:Arabidopsis Proteins; D060565:Argonaute Proteins; D018398:Homeodomain Proteins; D035683:MicroRNAs; D009687:Nuclear Proteins; C117457:AGO1 protein, Arabidopsis; C529694:AT5G43810 protein, Arabidopsis; C499534:APETALA2 protein, Arabidopsis; C493946:HD-Zip protein, Arabidopsis; C116421:WUSCHEL protein, Arabidopsis