Journal Article

A parthenogenesis gene of apomict origin elicits embryo formation from unfertilized eggs in a sexual plant

Conner, Joann A., Chae, Keun, Ozias-Akins, Peggy, Mookkan, Muruganantham, Huo, Heqiang

2015

Overview

Apomixis is a naturally occurring mode of asexual reproduction in flowering plants that results in seed formation without the involvement of meiosis or fertilization of the egg. Seeds formed on an apomictic plant contain offspring genetically identical to the maternal plant. Apomixis has significant potential for preserving hybrid vigor from one generation to the next in highly productive crop plant genotypes. ApomicticPennisetum/Cenchrusspecies, members of the Poaceae (grass) family, reproduce by apospory. Apospory is characterized by apomeiosis, the formation of unreduced embryo sacs derived from nucellar cells of the ovary and, by parthenogenesis, the development of the unreduced egg into an embryo without fertilization. InPennisetum squamulatum (L.) R.Br., apospory segregates as a single dominant locus, the aposporyspecific genomic region (ASGR). In this study, we demonstrate that thePsASGR-BABY BOOM-like(PsASGR-BBML) gene is expressed in egg cells before fertilization and can induce parthenogenesis and the production of haploid offspring in transgenic sexual pearl millet. A reduction ofPsASGR-BBMLexpression in apomictic F₁ RNAi transgenic plants results in fewer visible parthenogenetic embryos and a reduction of embryo cell number compared with controls. Our results endorse a key role forPsASGR-BBMLin parthenogenesis and a newly discovered role for a member of the BBM-like clade of APETALA 2 transcription factors. Induction of parthenogenesis byPsASGR-BBMLwill be valuable for installing parthenogenesis to synthesize apomixis in crops and will have further application for haploid induction to rapidly obtain homozygous lines for breeding.

• Publisher: National Academy of Sciences,National Acad Sciences
• Subject: Amino Acid Sequence / apomixis / Apomixis - genetics / asexual reproduction / Biological Sciences / Cenchrus / Cenchrus - embryology / Cenchrus - growth & development / Cenchrus americanus / Cenchrus squamulatus / crops / eggs / Embryos / Flowering plants / Gene Expression Profiling / Gene Expression Regulation, Developmental / Gene Expression Regulation, Plant / Genes / Genes, Plant - genetics / genomics / Genotypes / grasses / haploidy / heterosis / homozygosity / loci / meiosis / Molecular Sequence Data / Offspring / Oligonucleotide Array Sequence Analysis / Ovule - embryology / Ovule - genetics / parthenogenesis / Parthenogenesis - genetics / Pennisetum / Pennisetum - embryology / Pennisetum - genetics / Phylogeny / Plant Proteins - classification / Plant Proteins - genetics / Plant reproduction / Plants, Genetically Modified / Poaceae / Poaceae - embryology / Poaceae - genetics / progeny / Reverse Transcriptase Polymerase Chain Reaction / RNA Interference / Seeds / Seeds - embryology / Seeds - genetics / Sequence Homology, Amino Acid / Transgenic plants