title: Developmentally regulated HEART STOPPER, a mitochondrially targeted L18 ribosomal protein gene, is required for cell division, differentiation, and seed development in Arabidopsis.
abstract: Evidence is presented for the role of a mitochondrial ribosomal (mitoribosomal) L18 protein in cell division, differentiation, and seed development after the characterization of a recessive mutant, heart stopper (hes). The hes mutant produced uncellularized endosperm and embryos arrested at the late globular stage. The mutant embryos differentiated partially on rescue medium with some forming callus. HES (At1g08845) encodes a mitochondrially targeted member of a highly diverged L18 ribosomal protein family. The substitution of a conserved amino residue in the hes mutant potentially perturbs mitoribosomal function via altered binding of 5S rRNA and/or influences the stability of the 50S ribosomal subunit, affecting mRNA binding and translation. Consistent with this, marker genes for mitochondrial dysfunction were up-regulated in the mutant. The slow growth of the endosperm and embryo indicates a defect in cell cycle progression, which is evidenced by the down-regulation of cell cycle genes. The down-regulation of other genes such as EMBRYO DEFECTIVE genes links the mitochondria to the regulation of many aspects of seed development. HES expression is developmentally regulated, being preferentially expressed in tissues with active cell division and differentiation, including developing embryos and the root tips. The divergence of the L18 family, the tissue type restricted expression of HES, and the failure of other L18 members to complement the hes phenotype suggest that the L18 proteins are involved in modulating development. This is likely via heterogeneous mitoribosomes containing different L18 members, which may result in differential mitochondrial functions in response to different physiological situations during development.
authors.affiliation: Rice Research Institute of Sichuan Agricultural University, Chengdu, Sichuan 611130, PR China.
authors.forename: Hongyu
authors.initials: H
authors.lastname: Zhang
authors.affiliation: CSIRO Agriculture Flagship, PO Box 1600, ACT 2601, Australia ming.luo@csiro.au.
authors.forename: Ming
authors.initials: M
authors.lastname: Luo
authors.affiliation: Department of Biochemistry, University of Otago, Dunedin, New Zealand.
authors.forename: Robert C
authors.initials: RC
authors.lastname: Day
authors.affiliation: CSIRO Agriculture Flagship, PO Box 1600, ACT 2601, Australia.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Talbot
authors.affiliation: CSIRO Agriculture Flagship, PO Box 1600, ACT 2601, Australia Present address: ARC Centre of Excellence in Plant Energy Biology, The University of Western Australia, WA 6009, Australia.
authors.forename: Aneta
authors.initials: A
authors.lastname: Ivanova
authors.affiliation: CSIRO Agriculture Flagship, PO Box 1600, ACT 2601, Australia.
authors.forename: Anthony R
authors.initials: AR
authors.lastname: Ashton
authors.affiliation: CSIRO Agriculture Flagship, PO Box 1600, ACT 2601, Australia Present address: VitaGrain, 232 Orchard Road, Level 9, Suite 232, Faber House, 238854 Singapore.
authors.forename: Abed M
authors.initials: AM
authors.lastname: Chaudhury
authors.affiliation: Department of Biochemistry, University of Otago, Dunedin, New Zealand.
authors.forename: Richard C
authors.initials: RC
authors.lastname: Macknight
authors.affiliation: Australian Centre for Plant Functional Genomics, School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, SA 5064, Australia.
authors.forename: Maria
authors.initials: M
authors.lastname: Hrmova
authors.affiliation: CSIRO Agriculture Flagship, PO Box 350, Glen Osmond, SA 5064, Australia.
authors.forename: Anna M
authors.initials: AM
authors.lastname: Koltunow
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D002454:Cell Differentiation; D002455:Cell Division; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D009154:Mutation; D010802:Phylogeny; D012269:Ribosomal Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D012639:Seeds / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D029681:Arabidopsis Proteins; D012269:Ribosomal Proteins; C029609:ribosomal protein L18
keywords: Cellularization; development; differentiation; embryo; endosperm; lethality; mitochondria; ribosome; ros; seed.