Uniparental and transgressive expression of α-zeins in maize endosperm of o2 hybrid lines

PLoS One. 2018 Nov 15;13(11):e0206993. doi: 10.1371/journal.pone.0206993. eCollection 2018.

Abstract

The α-zein gene family encodes the most abundant storage proteins of maize (Zea mays) endosperm. Members of this family are expressed in a parent-of-origin manner. To characterize this phenomenon further, we investigated the expression of a subset of α-zein polypeptides in reciprocal crosses between o2 lines that were characterized by a simplified α-zein pattern. Maize lines that suppressed the expression of α-zeins when used as female parents were identified. The suppression was cross-specific, occurring only when specific genetic backgrounds were combined. Four α-zein sequences that were sensitive to uniparental expression were isolated. Molecular characterization of these α-zeins confirmed that their expression or suppression depended on the genetic proprieties of the endosperm tissue instead of their parental origin. DNA methylation analysis of both maternally and paternally expressed α-zeins revealed no clear correlation between this epigenetic marker and parent-of-origin allelic expression, suggesting that an additional factor(s) is involved in this process. Genetic analyses revealed that the ability of certain lines to suppress α-zein expression was unstable after one round of heterozygosity with non-suppressing lines. Interestingly, α-zeins also showed a transgressive expression pattern because unexpressed isoforms were reactivated in both F2 and backcross plants. Collectively, our results suggest that parent-of-origin expression of specific α-zein alleles depends on a complex interaction between genotypes in a manner that is reminiscent of paramutation-like phenomena.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alleles
  • Amino Acid Sequence
  • Chimera / genetics
  • DNA Methylation
  • DNA, Plant / chemistry
  • DNA, Plant / genetics
  • DNA, Plant / metabolism
  • Endosperm / metabolism
  • Gene Expression Regulation, Plant
  • Genotype
  • Plant Proteins / genetics
  • Plant Proteins / metabolism*
  • Protein Isoforms / genetics
  • Protein Isoforms / metabolism
  • Sequence Alignment
  • Zea mays / metabolism*
  • Zein / genetics
  • Zein / metabolism*

Substances

  • DNA, Plant
  • Plant Proteins
  • Protein Isoforms
  • Zein

Grants and funding

Research was supported by a grant from MIUR, FIRB project no. RBNE01TYZF, and a special grant from MIUR and CNR for the Epigenomics Flagship Project (EPIGEN). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.