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

• Published in: PloS one 2018-11, Vol.13 (11), p.e0206993-e0206993
• Main Authors: Castelli, Silvana, Mascheretti, Iride, Cosentino, Cristian, Lazzari, Barbara, Pirona, Raul, Ceriotti, Aldo, Viotti, Angelo, Lauria, Massimiliano
• Format: Article
• Language: English
• Subjects: Biology and Life Sciences; Corn; Deoxyribonucleic acid; DNA; DNA methylation; Endosperm; Epigenetics; Flowers & plants; Gene amplification; Gene expression; Gene sequencing; Genetic analysis; Genetic engineering; Genomes; Genotypes; Heterozygosity; Isoforms; Parents; Plant tissues; Polypeptides; Proteins; Research and Analysis Methods; Seeds; Storage proteins; Transcription factors; Zea mays; Zein
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0206993

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.