Abstract
Genomic imprinting confers parent-of-origin-specific gene expression, thus non-equivalent and complementary function of parental genomes. As a consequence, genomic imprinting poses an epigenetic barrier to parthenogenesis in sexual organisms. We report aberrant imprinting in Boechera, a genus in which apomicts evolved from sexuals multiple times. Maternal activation of a MADS-box gene, a homolog of which is imprinted and paternally expressed in the sexual relative Arabidopsis, is accompanied by locus-specific DNA methylation changes in apomicts where parental imprinting seems to be relaxed.
Highlights
Genomic imprinting refers to epigenetic gene regulation that leads to the parent-of-origin-specific expression of alleles, and it was proposed to differentially control offspring developmentreviewed in 1
Preventing pollination in Apo-1 did not lead to parthenogenetic embryo development (Fig. 1h), further supporting the view that some aspects of fertilization are necessary for parthenogenesis in Boechera
Unlike egg-sperm karyogamy leading to zygote formation in the sexual (Fig. 1i,l), the second sperm nucleus in the apomicts persisted in the vicinity of the nucleus of the egg but no fusion occurred even at a stage when mitotic divisions in the endosperm advanced (Fig. 1k,m–p). This observation suggests that presence of the sperm near the egg cell of the apomict might serve as activation source to induce pseudogamous parthenogenesis
Summary
Olga Kirioukhova[1,2], Jubin N. The maternal allele of PHEL1 is expressed in the embryo and endosperm tissues of the Boechera sexuals (Fig. 2a, Supplementary Fig. 6b,c), unlike its Arabidopsis counterpart PHE114. PHEL1 expression in the apomicts showed 250–400-fold higher transcript levels in female than male floral organs and in the embryos compared to the levels of expression in the sexual (Fig. 2b) We propose that these high levels of the maternal PHEL1 transcript prior and during embryo development may play a role in parthenogenesis. Our findings suggest that parent-of-origin expression of PHEL1 or PHE115 across genera is highly correlated with DNA methylation pattern of the corresponding loci; this regulation is modified in Boechera in terms of a) reversion of the imprinting status resulting in expression of the maternal PHEL1 allele; and b) deletion of the heavily methylated 3′MR in the alleles specific to apomicts, with a concomitant increase in expression. We propose that alterations in the control of genomic imprinting enable the adjustment of parental gene dosage necessary for parthenogenesis to evolve
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
