Ploidy variation in multinucleate cells changes under stress

Mol Biol Cell. 2015 Mar 15;26(6):1129-40. doi: 10.1091/mbc.E14-09-1375. Epub 2015 Jan 28.

Abstract

Ploidy variation is found in contexts as diverse as solid tumors, drug resistance in fungal infection, and normal development. Altering chromosome or genome copy number supports adaptation to fluctuating environments but is also associated with fitness defects attributed to protein imbalances. Both aneuploidy and polyploidy can arise from multinucleate states after failed cytokinesis or cell fusion. The consequences of ploidy variation in syncytia are difficult to predict because protein imbalances are theoretically buffered by a common cytoplasm. We examined ploidy in a naturally multinucleate fungus, Ashbya gossypii. Using integrated lac operator arrays, we found that chromosome number varies substantially among nuclei sharing a common cytoplasm. Populations of nuclei range from 1N to >4N, with different polyploidies in the same cell and low levels of aneuploidy. The degree of ploidy variation increases as cells age. In response to cellular stress, polyploid nuclei diminish and haploid nuclei predominate. These data suggest that mixed ploidy is tolerated in these syncytia; however, there may be costs associated with variation as stress homogenizes the genome content of nuclei. Furthermore, the results suggest that sharing of gene products is limited, and thus there is incomplete buffering of ploidy variation despite a common cytosol.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Ascomycota / cytology
  • Ascomycota / genetics*
  • Ascomycota / growth & development
  • Cell Nucleus / genetics
  • Chromosome Segregation
  • Chromosomes, Fungal / genetics
  • DNA, Fungal / genetics
  • Fungal Proteins / physiology
  • Gene Dosage
  • Genes, Fungal
  • Mad2 Proteins / physiology
  • Polyploidy
  • Stress, Physiological

Substances

  • DNA, Fungal
  • Fungal Proteins
  • Mad2 Proteins