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Sex-Biased Lethality or Transmission of Defective Transcription Machinery in Arabidopsis

Sex-Biased Lethality or Transmission of Defective Transcription Machinery in Arabidopsis,10.1534/genetics.108.090621,Genetics,Yasuyuki Onodera,Kosuke

Sex-Biased Lethality or Transmission of Defective Transcription Machinery in Arabidopsis   (Citations: 7)
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Unlike animals, whose gametes are direct products of meiosis, plant meiotic products undergo addi- tional rounds of mitosis, developing into multicellular haploid gametophytes that produce egg or sperm cells. The complex development of gametophytes requires extensive expression of the genome, with DNA- dependent RNA polymerases I, II, and III being the key enzymes for nuclear gene expression. We show that loss-of-function mutations in genes encoding key subunits of RNA polymerases I, II, or III are not transmitted maternally due to the failure of female megaspores to complete the three rounds of mitosis required for the development of mature gametophytes. However, male microspores bearing defective polymerase alleles develop into mature gametophytes (pollen) that germinate, grow pollen tubes, fertilize wild-type female gametophytes, and transmit the mutant genes to the next generation at moderate fre- quency. These results indicate that female gametophytes are autonomous with regard to gene expression, relying on transcription machinery encoded by their haploid nuclei. By contrast, male gametophytes make extensive use of transcription machinery that is synthesized by the diploid parent plant (sporophyte) and persists in mature pollen. As a result, the expected stringent selection against nonfunctional essential genes in the haploid state occurs in the female lineage but is relaxed in the male lineage.
Journal: Genetics , vol. 180, no. 1, pp. 207-218, 2008
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    • ...The genes encoding the atypical largest and second-largest polymerase subunits in Arabidopsis are not essential for viability (Herr et al., 2005; Kanno et al., 2005; Onodera et al., 2005; Pontier et al., 2005), unlike their Pol I, II, or III counterparts (Onodera et al., 2008)...
    • ...The significant number ofPol II-like subunits in Pol IV andPol V raised questions concerning the relative similarities of Pol II, Pol IV, and Pol V. Therefore, we affinity purified Arabidopsis Pol II by exploiting epitope-tagged NRPB2 (NRPB2-FLAG) expressed from a transgene that rescues the nrpb2-1 null mutant (Onodera et al., 2008)...
    • ...Pol I, II, and III second-largest subunits (NRPA2-FLAG, NRPB2-FLAG, or NRPC2-FLAG) or FLAG-tagged Pol IV and Pol V largest subunits (NRPD1-FLAG, NRPE1-FLAG), each expressed from trangenes that rescue corresponding null mutants (Onodera et al., 2008; Pontes et al., 2006)...
    • ...In contrast, homozygous nrpd5-1/nrpb5-1 T-DNA insertion mutants were not recoverable due to female gametophyte lethality, as shown by reciprocal genetic crosses (Figures S14AandS14B).Femalegametophytelethalityisacharacteristic of Pol I, II, and III mutants, as demonstrated previously for nrpa2, nrpb2, nrpc2, and nrpb12 (Onodera et al., 2008)...
    • ...The fact that Pol IV and Pol V share numerous small subunits with Pol II, including NRPB3, NRPB6, NRPB8, NRPB9, NRPB10, NRPB11, and NRPB12 family subunits, can explain why alleles for these genes have not been identified in genetic screens; loss-of-function mutations in the subunits of essential polymerases cause female gametophyte lethality (Figure S14 )( Onodera et al., 2008)...
    • ...previously described (Onodera et al., 2008; Pontes et al., 2006)...

    Thomas S. Reamet al. Subunit Compositions of the RNA-Silencing Enzymes Pol IV and Pol V Rev...

    • ...The NRPD1 (NRPD1a), NRPE1 (NRPD1b) and NRPD2/NRPE2 genes are not essential for viability [5,6,9,10], unlike the genes encoding the equivalent subunits of Pol I, II and III [5,11]...

    Jeremy R. Haaget al. Metal A and Metal B Sites of Nuclear RNA Polymerases Pol IV and Pol V ...

    • ...as were nrdp1b-11 NRPD1b-FLAG (NRPE1-FLAG )( Pontes et al., 2006) and NRPB2-FLAG (Onodera et al., 2008) transgenic lines...

    Andrzej T. Wierzbickiet al. NoncodingTranscriptionbyRNAPolymerase Pol IVb/Pol V Mediates Transcrip...

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