The presence of β'1-COP and β'2-COP is required for female and male gametophyte development.

Coat protein I (COPI) and Coat protein II (COPII) coated vesicles mediate protein transport in the early secretory pathway. Although several components of COPII vesicles have been shown to have an essential role in Arabidopsis gametogenesis, the function of COPI components in gametogenesis has not been studied in detail. COPI consists of a heptameric complex made of α, β, β', γ, δ, ɛ, and ζ-COP subunits and most subunits have several isoforms in Arabidopsis. We have found that two isoforms of the β'-COP subunit, β'1-COP and β'2-COP, are required for female and male gametophyte development. Reciprocal crosses between wild type plants and plants heterozygous for T-DNA insertions in β'1-COP and β'2-COP showed that β'1β'2-cop gametophytes are not transmitted.