bims-plasge Biomed news
on Plastid genes
Issue of 2019‒04‒07
two papers selected by
Vera S. Bogdanova
Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences

  1. Mol Phylogenet Evol. 2019 Apr 01. pii: S1055-7903(19)30087-9. [Epub ahead of print]
    Nemati Z, Harpke D, Gemicioglu A, Kerndorff H, Blattner FR.
      Crocus sativus, the saffron crocus, is the source of saffron, which is made from the dried stigmas of the plant. It is a male-sterile triploid lineage that ever since its origin has been propagated vegetatively. Its mode of evolution and area of origin are matters of long-lasting debates. Here we analyzed chloroplast genomes and genome-wide DNA polymorphisms obtained through genotyping-by-sequencing (GBS) to infer the parent and area of origin of C. sativus. These data were complemented by genome size measurements and analyses of nuclear single-copy genes. We could place 99.3% of saffron GBS alleles in Crocus cartwrightianus, a species occurring in southeastern mainland Greece and on Aegean islands, identifying it as the sole progenitor of the saffron crocus. Phylogenetic and population assignment analyses together with chloroplast polymorphisms indicated the C. cartwrightianus population in the vicinity of Athens as most similar to C. sativus. We conclude that the crop is an autotriploid that evolved in Attica by combining two different genotypes of C. cartwrightianus. Triploid sterility and vegetative propagation prevented afterwards segregation of the favorable traits of saffron, resulting in worldwide cultivation of a unique clonal lineage.
    Keywords:  Crocus; autotriploidy; crop evolution; domestication; genotyping-by-sequencing; saffron
  2. Mol Biol Evol. 2019 Feb 19. pii: msz031. [Epub ahead of print]
    Lama S, Broda M, Abbas Z, Vaneechoutte D, Belt K, Säll T, Vandepoele K, Van Aken O.
      Because of their symbiotic origin, many mitochondrial proteins are well conserved across eukaryotic kingdoms. It is however less obvious how specific lineages have obtained novel nuclear-encoded mitochondrial proteins. Here, we report a case of mitochondrial neofunctionalization in plants. Phylogenetic analysis of genes containing the Domain of Unknown Function 295 (DUF295) revealed that the domain likely originated in Angiosperms. The C-terminal DUF295 domain is usually accompanied by an N-terminal F-box domain, involved in ubiquitin ligation via binding with ASK1/SKP1-type proteins. Due to gene duplication, the gene family has expanded rapidly, with 94 DUF295-related genes in Arabidopsis thaliana alone. Two DUF295 family subgroups have uniquely evolved and quickly expanded within Brassicaceae. One of these subgroups has completely lost the F-box, but instead obtained strongly predicted mitochondrial targeting peptides. We show that several representatives of this DUF295 Organellar group are effectively targeted to plant mitochondria and chloroplasts. Furthermore, many DUF295 Organellar genes are induced by mitochondrial dysfunction, whereas F-Box DUF295 genes are not. In agreement, several Brassicaceae-specific DUF295 Organellar genes were incorporated in the evolutionary much older ANAC017-dependent mitochondrial retrograde signaling pathway. Finally, a representative set of DUF295 T-DNA insertion mutants was created. No obvious aberrant phenotypes during normal growth and mitochondrial dysfunction were observed, most likely due to the large extent of gene duplication and redundancy. Overall, this study provides insight into how novel mitochondrial proteins can be created via "intercompartmental" gene duplication events. Moreover, our analysis shows that these newly evolved genes can then be specifically integrated into relevant, pre-existing coexpression networks.
    Keywords:  evolution; mitochondria; neofunctionalization; retrograde signaling; stress