title: Transcription of nuclear organellar DNA in a model plant system.
abstract: Endosymbiotic gene transfer from cytoplasmic organelles (chloroplasts and mitochondria) to the nucleus is an ongoing process in land plants. Although the frequency of organelle DNA migration is high, functional gene transfer is rare because a nuclear promoter is thought necessary for activity in the nucleus. Here we show that a chloroplast promoter, 16S rrn, drives nuclear transcription, suggesting that a transferred organellar gene may become active without obtaining a nuclear promoter. Examining the chromatin status of a known de novo chloroplast integrant indicates that plastid DNA inserts into open chromatin and that this relaxed condition is maintained after integration. Transcription of nuclear organelle DNA integrants was explored at the whole genome level by analyzing RNA-seq data of Oryza sativa subsp. japonica, and utilizing sequence polymorphisms to unequivocally discriminate nuclear organelle DNA transcripts from those of bona fide cytoplasmic organelle DNA. Nuclear copies of organelle DNA that are transcribed show a spectrum of transcriptional activity but at comparatively low levels compared with the majority of other nuclear genes.
authors.affiliation: Shanghai Center for Plant Stress Biology, Shanghai Institute for Biological Science, Chinese Academy of Sciences, Shanghai, China dongwangbio@gmail.com.
authors.forename: Dong
authors.initials: D
authors.lastname: Wang
authors.affiliation: Discipline of Genetics, School of Molecular and Biomedical Science, The University of Adelaide, South Australia, Australia.
authors.forename: Zhipeng
authors.initials: Z
authors.lastname: Qu
authors.affiliation: Discipline of Genetics, School of Molecular and Biomedical Science, The University of Adelaide, South Australia, Australia.
authors.forename: David L
authors.initials: DL
authors.lastname: Adelson
authors.affiliation: Shanghai Center for Plant Stress Biology, Shanghai Institute for Biological Science, Chinese Academy of Sciences, Shanghai, China.
authors.forename: Jian-Kang
authors.initials: JK
authors.lastname: Zhu
authors.affiliation: Discipline of Genetics, School of Molecular and Biomedical Science, The University of Adelaide, South Australia, Australia.
authors.forename: Jeremy N
authors.initials: JN
authors.lastname: Timmis
mesh_terms: D001483:Base Sequence; D002467:Cell Nucleus / Q000235:genetics*; D018742:DNA, Chloroplast / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics*; D018506:Gene Expression Regulation, Plant; D012275:Oryza / Q000235:genetics*; D018087:Plastids / Q000235:genetics; D011401:Promoter Regions, Genetic; D014158:Transcription, Genetic
chemical_list: D018742:DNA, Chloroplast; D018744:DNA, Plant
keywords: endosymbiotic gene transfer; nuclear integrants of organellar DNA; open chromatin