bims-plasge Biomed News
on Plastid genes
Issue of 2021‒06‒27
two papers selected by
Vera S. Bogdanova
Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences

  1. Plant Reprod. 2021 Jun 24.
      KEY MESSAGE: Characterization of hybrid seed failure in Prunus provides insight into conserved or lineage-specific hybrid incompatibility mechanisms in plant species. Postzygotic hybrid incompatibility resulting from a cross between different species involves complex mechanisms occurring at various developmental stages. Embryo arrest, followed by seed abortion, is the first stage of such incompatibility reactions and inhibits hybrid seed development. In Prunus, a rosaceous woody species, some interspecific crosses result in fruit drop during the early stage of fruit development, in which inferior seed development may be accounted for the observed hybrid incompatibility. In this study, we investigated ovule development and the transcriptomes of developing ovules in inter-subgeneric crosses of Prunus. We conducted a cross of Prunus mume (subgenus Prunus), pollinated by P. persica (subgenus Amygdalus), and found that ovule and seed coat degeneration occurs before fruit drop. Transcriptome analysis identified differentially expressed genes enriched in several GO pathways, including organelle development, stimulus response, and signaling. Among these pathways, the organelle-related genes were actively regulated during ovule development, as they showed higher expression in the early stage of interspecific crosses and declined in the later stage, suggesting that the differential regulation of organelle function may induce the degeneration of hybrid ovules. Additionally, genes related to ovule and seed coat development, such as genes encoding AGL-like and auxin response, were differentially regulated in Prunus interspecific crosses. Our results provide histological and molecular information on hybrid seed abortion in Prunus that could be utilized to develop new hybrid crops. Additionally, we compared and discussed transcriptome responses to hybrid seed failure in Prunus and other plant species, which provides insight into conserved or lineage-specific hybrid incompatibility mechanisms in some plant species.
    Keywords:  Embryo arrest; Interspecific hybridization; Ovule development; Postzygotic barrier; Prunus
  2. Mol Phylogenet Evol. 2021 Jun 17. pii: S1055-7903(21)00169-X. [Epub ahead of print] 107236
      Plant specific mitoviruses in the 'genus' Mitovirus (Narnaviridae) and their integrated sequences (non-retroviral endogenous RNA viral elements or NERVEs) have been recently identified in various plant lineages. However, the sparse phylogenetic coverage of complete plant mitochondrial genome (mitogenome) sequences and the non-conserved nature of mitochondrial intergenic regions have hindered comparative studies on mitovirus NERVEs in plants. In this study, 10 new mitogenomes were sequenced from legumes (Fabaceae). Based on comparative genomic analysis of 27 total mitogenomes, we identified mitovirus NERVEs and transposable elements across the family. All legume mitogenomes included NERVEs and total NERVE length varied from ca. 2 kb in the papilionoid Trifolium to 35 kb in the mimosoid Acacia. Most of the NERVE integration sites were in highly variable intergenic regions, however, some were positioned in six cis-spliced mitochondrial introns. In the Acacia mitogenome, there were L1-like transposons including an almost full-length copy with target site duplications (TSDs). The integration sites of NERVEs in four introns showed evidence of L1-like retrotransposition events. Phylogenetic analysis revealed that there were multiple instances of precise deletion of NERVEs between TSDs. This study provides clear evidence that a L1-like retrotransposition mechanism has a long history of contributing to the integration of viral RNA into plant mitogenomes while microhomology-mediated deletion can restore the integration site.
    Keywords:  comparative genomics; group II intron; horizontal gene transfer; intracellular gene transfer; target primed reverse transcription