Department of Biology, University of Brasília-UnB, Campus Darcy Ribeiro S/N-Asa Norte, Brasília, DF, 70910-900, Brazil.
Embrapa Genetic Resources and Biotechnology, Parque Estação Biológica, PqEB Av. W5 Norte, Caixa Postal 02372, Brasília, DF, 70770-917, Brazil.
Plant Cell Rep. 2018 Feb;37(2):293-306. doi: 10.1007/s00299-017-2230-0. Epub 2017 Oct 28.
BbrizGID1 is expressed in the nucellus of apomictic Brachiaria brizantha, previous to aposporous initial differentiation. AtGID1a overexpression triggers differentiation of Arabidopsis thaliana MMC-like cells, suggesting its involvement in ovule development. GIBBERELLIN-INSENSITIVE DWARF1 (GID1) is a gibberellin receptor previously identified in plants and associated with reproductive development, including ovule formation. In this work, we characterized the Brachiaria brizantha GID1 gene (BbrizGID1). BbrizGID1 showed up to 92% similarity to GID1-like gibberellin receptors of other plants of the Poaceae family and around 58% to GID1-like gibberellin receptors of Arabidopsis thaliana. BbrizGID1 was more expressed in ovaries at megasporogenesis than in ovaries at megagametogenesis of both sexual and apomictic plants. In ovules, BbrizGID1 transcripts were detected in the megaspore mother cell (MMC) of sexual and apomictic B. brizantha. Only in the apomictic plants, expression was also observed in the surrounding nucellar cells, a region in which aposporous initial cells differentiate to form the aposporic embryo sac. AtGID1a ectopic expression in Arabidopsis determines the formation of MMC-like cells in the nucellus, close to the MMC, that did not own MMC identity. Our results suggest that GID1 might be involved in the proper differentiation of a single MMC during ovule development and provide valuable information on the role of GID1 in sexual and apomictic reproduction.
BbrizGID1 在无融合生殖 Brachiaria brizantha 的珠心表达，早于无孢子原基的分化。AtGID1a 的过表达触发拟南芥 MMC 样细胞的分化，提示其参与胚珠发育。赤霉素不敏感矮化 1 型（GID1）是一种先前在植物中发现的赤霉素受体，与生殖发育有关，包括胚珠的形成。在这项工作中，我们对 Brachiaria brizantha GID1 基因（BbrizGID1）进行了表征。BbrizGID1 与其他禾本科植物的 GID1 样赤霉素受体的相似性高达 92%，与拟南芥的 GID1 样赤霉素受体的相似性约为 58%。BbrizGID1 在大孢子母细胞（MMC）减数分裂期的表达高于有性和无融合生殖植物的大孢子母细胞减数分裂期。在胚珠中，BbrizGID1 转录本在有性和无融合生殖的 B. brizantha 的 MMC 中被检测到。只有在无融合生殖植物中，在周围珠心细胞中也观察到表达，这是一个无孢子原基细胞分化形成无孢子胚囊的区域。AtGID1a 在拟南芥中的异位表达决定了 MMC 样细胞在珠心的形成，靠近 MMC，但不具有 MMC 的特性。我们的结果表明，GID1 可能参与了胚珠发育过程中单一大孢子母细胞的适当分化，并为 GID1 在有性和无融合生殖中的作用提供了有价值的信息。
