title: MicroRNA-mediated repression of the seed maturation program during vegetative development in Arabidopsis.
abstract: The seed maturation program only occurs during late embryogenesis, and repression of the program is pivotal for seedling development. However, the mechanism through which this repression is achieved in vegetative tissues is poorly understood. Here we report a microRNA (miRNA)-mediated repression mechanism operating in leaves. To understand the repression of the embryonic program in seedlings, we have conducted a genetic screen using a seed maturation gene reporter transgenic line in Arabidopsis (Arabidopsis thaliana) for the isolation of mutants that ectopically express seed maturation genes in leaves. One of the mutants identified from the screen is a weak allele of ARGONAUTE1 (AGO1) that encodes an effector protein for small RNAs. We first show that it is the defect in the accumulation of miRNAs rather than other small RNAs that causes the ectopic seed gene expression in ago1. We then demonstrate that overexpression of miR166 suppresses the derepression of the seed gene reporter in ago1 and that, conversely, the specific loss of miR166 causes ectopic expression of seed maturation genes. Further, we show that ectopic expression of miR166 targets, type III homeodomain-leucine zipper (HD-ZIPIII) genes PHABULOSA (PHB) and PHAVOLUTA (PHV), is sufficient to activate seed maturation genes in vegetative tissues. Lastly, we show that PHB binds the promoter of LEAFY COTYLEDON2 (LEC2), which encodes a master regulator of seed maturation. Therefore, this study establishes a core module composed of a miRNA, its target genes (PHB and PHV), and the direct target of PHB (LEC2) as an underlying mechanism that keeps the seed maturation program off during vegetative development.
authors.affiliation: Agriculture and Agri-Food Canada, Southern Crop Protection and Food Research Centre, London, Ontario, Canada.
authors.forename: Xurong
authors.initials: X
authors.lastname: Tang
authors.forename: Shaomin
authors.initials: S
authors.lastname: Bian
authors.forename: Mingjuan
authors.initials: M
authors.lastname: Tang
authors.forename: Qing
authors.initials: Q
authors.lastname: Lu
authors.forename: Shengben
authors.initials: S
authors.lastname: Li
authors.forename: Xigang
authors.initials: X
authors.lastname: Liu
authors.forename: Gang
authors.initials: G
authors.lastname: Tian
authors.forename: Vi
authors.initials: V
authors.lastname: Nguyen
authors.forename: Edward W T
authors.initials: EW
authors.lastname: Tsang
authors.forename: Aiming
authors.initials: A
authors.lastname: Wang
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Rothstein
authors.forename: Xuemei
authors.initials: X
authors.lastname: Chen
authors.forename: Yuhai
authors.initials: Y
authors.lastname: Cui
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D060565:Argonaute Proteins / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017930:Genes, Reporter; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D018515:Plant Leaves / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D012639:Seeds / Q000235:genetics / Q000254:growth & development
chemical_list: C117457:AGO1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D060565:Argonaute Proteins; D018398:Homeodomain Proteins; C580969:MIRN166 microRNA, Arabidopsis; D035683:MicroRNAs; C114647:PHB protein, Arabidopsis; C114644:PHV protein, Arabidopsis