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Type: Journal article
Title: Enlarging cells initiating apomixis in Hieracium praealtum transition to an embryo sac program prior to entering mitosis
Author: Okada, T.
Hu, Y.
Tucker, M.
Taylor, J.
Johnson, S.
Spriggs, A.
Tsuchiya, T.
Oelkers, K.
Rodrigues, J.
Koltunow, A.
Citation: Plant Physiology, 2013; 163(1):216-231
Publisher: American Society of Plant Biologists
Issue Date: 2013
ISSN: 0032-0889
Statement of
Takashi Okada, Yingkao Hu, Matthew R. Tucker, Jennifer M. Taylor, Susan D. Johnson, Andrew Spriggs, Tohru Tsuchiya, Karsten Oelkers, Julio C.M. Rodrigues and Anna M.G. Koltunow
Abstract: Hieracium praealtum forms seeds asexually by apomixis. During ovule development, sexual reproduction initiates with megaspore mother cell (MMC) entry into meiosis and formation of a tetrad of haploid megaspores. The sexual pathway ceases when a diploid aposporous initial (AI) cell differentiates, enlarges and undergoes mitosis forming an aposporous embryo (AE) sac that displaces sexual structures. Embryo and endosperm development in AE sacs is fertilization-independent. Transcriptional data relating to apomixis initiation in Hieracium ovules is scarce and the functional identity of the AI cell relative to other ovule cell types is unclear. Enlarging AI cells with undivided nuclei, early aposporous embryo (EAE) sacs containing two to four nuclei, and random groups of sporophytic ovule (SO) cells not undergoing these events were collected by laser capture microdissection (LCM). Isolated amplified mRNA samples were sequenced using the 454 pyrosequencing platform and comparatively analysed to establish indicative roles of the captured cell types. Transcriptome and protein motif analyses showed that approximately half of the assembled contigs identified homologous sequences in Arabidopsis, of which the vast majority were expressed during early Arabidopsis ovule development. The SO cells were enriched in signaling functions. Gene expression indicative of meiosis was notably absent in enlarging AI cells, consistent with subsequent aposporous embryo sac formation without meiosis. The AI cell transcriptome was most similar to the EAE sac transcriptome when comparing known functional annotations and both shared expressed genes involved in gametophyte development, suggesting that the enlarging AI cell is already transitioning to an embryo sac program prior to mitotic division.
Keywords: Asteraceae
RNA, Plant
Signal Transduction
Models, Biological
Rights: © 2013 American Society of Plant Biologists. All Rights Reserved.
DOI: 10.1104/pp.113.219485
Appears in Collections:Agriculture, Food and Wine publications
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