bims-plasge Biomed News
on Plastid genes
Issue of 2020‒02‒09
two papers selected by
Vera S. Bogdanova
Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences

  1. Genes (Basel). 2020 Jan 28. pii: E134. [Epub ahead of print]11(2):
    Coate JE, Schreyer WM, Kum D, Doyle JJ.
      Polyploidy is hypothesized to cause dosage imbalances between the nucleus and the other genome-containing organelles (mitochondria and plastids), but the evidence for this is limited. We performed RNA-seq on Arabidopsis thaliana diploids and their derived autopolyploids to quantify the degree of inter-genome coordination of transcriptional responses to nuclear whole genome duplication in two different organs (sepals and rosette leaves). We show that nuclear and organellar genomes exhibit highly coordinated responses in both organs. First, organelle genome copy number increased in response to nuclear whole genome duplication (WGD), at least partially compensating for altered nuclear genome dosage. Second, transcriptional output of the different cellular compartments is tuned to maintain diploid-like levels of relative expression among interacting genes. In particular, plastid genes and nuclear genes whose products are plastid-targeted show coordinated down-regulation, such that their expression levels relative to each other remain constant across ploidy levels. Conversely, mitochondrial genes and nuclear genes with mitochondrial targeting show either constant or coordinated up-regulation of expression relative to other nuclear genes. Thus, cytonuclear coordination is robust to changes in nuclear ploidy level, with diploid-like balance in transcript abundances achieved within three generations after nuclear whole genome duplication.
    Keywords:  Arabidopsis thaliana; cytonuclear interactions; polyploidy; transcription
  2. J Evol Biol. 2020 Feb 03.
    Koski MH, Berardi A, Galloway LF.
      Color phenotypes are often involved in communication and are thus under selection by species interactions. However, selection may also act on color through correlated traits or alternative functions of biochemical pigments. Such forms of selection are instrumental in maintaining petal color diversity in plants. Pollen color also varies markedly, but the maintenance of this variation is little understood. In Campanula americana, pollen ranges from white to dark purple, with darker morphs garnering more pollinator visits and exhibiting elevated pollen performance under heat stress. Here, we generate an F2 population segregating for pollen color and measure correlations with floral traits, pollen attributes, and plant-level traits related to fitness. We determine the pigment biochemistry of color variants, and evaluate maternal and paternal fitness of light and dark morphs by crossing within and between morphs. Pollen color was largely uncorrelated with floral traits (petal color, size, nectar traits) suggesting it can evolve independently. Darker pollen grains were larger and had higher anthocyanin content (cyanidin and peonidin) which may explain why they outperform light pollen under heat stress. Overall, pollen-related fitness metrics were greater for dark pollen, and dark pollen sires generated seeds with higher germination potential. Conversely, light pollen plants produce 61% more flowers than dark, and 18% more seeds per fruit, suggesting a seed production advantage. Results indicate that light and dark morphs may achieve fitness through different means-dark morphs appear to have a pollen advantage while light morphs have an ovule advantage-helping to explain the maintenance of pollen color variation.
    Keywords:   Campanula americana ; anthocyanins; flavonoids; floral evolution; flower color; pollen color; pollen viability; trait correlation