The cellular and molecular biology of conifer embryogenesis

Abstract

511 Review SummaryGymnosperms and angiosperms are thought to have evolved from a common ancestor c . 300 million yr ago. The manner in which gymnosperms and angiosperms form seeds has diverged and, although broad similarities are evident, the anatomy and cell and molecular biology of embryogenesis in gymnosperms, such as the coniferous trees pine, spruce and fir, differ significantly from those in the most widely studied model angiosperm Arabidopsis thaliana . Molecular analysis of signaling pathways and processes such as programmed cell death and embryo maturation indicates that many developmental pathways are conserved between angiosperms and gymnosperms. Recent genomics research reveals that almost 30% of mRNAs found in developing pine embryos are absent from other conifer expressed sequence tag (EST) collections. These data show that the conifer embryo differs markedly from other gymnosperm tissues studied to date in terms of the range of genes transcribed. Approximately 72% of conifer embryo-expressed genes are found in the Arabidopsis proteome and conifer embryos contain mRNAs of very similar sequence to key genes that regulate seed development in Arabidopsis. However, 1388 loblolly pine ( Pinus taeda ) embryo ESTs (11.4% of the collection) are novel and, to date, have been found in no other plant. The data imply that, in gymnosperm embryogenesis, differences in structure and development are achieved by subtle molecular interactions, control of spatial and temporal gene expression and the regulating agency of a few unique proteins.New Phytologist (2007) 176 : 511-536

Identification of molecular processes that differ among Scots pine somatic embryogenic cell lines leading to the development of normal or abnormal cotyledonary embryos

“…Arabidopsis genes related to embryogenesis, 85% had a strong sequence similarity to an expressed sequence tag in the loblolly pine (Pinus taeda) database (Cairney and Pullman 2007). However, it is important to gain knowledge about the temporal and spatial expression pattern for different genes in order to understand the fundamentals of embryogenesis in conifers.…”

Pine embryogenesis

“…In conifer seeds, similar kind of recognition may take place between the megagametophyte and embryos during the different stages of embryogenesis. Expressed sequence tags (ESTs) of loblolly pine (Pinus taeda L.) embryos 36 together with identified loblolly pine microRNAs (miRNAs) that modulate in the megagametophyte and zygotic embryo stage-specifically will help to unravel the actual signal cascades directing the development of different conifer seed tissues.…”

Forest tree genomics: 10 achievements from the past 10 years and future prospects

“…The number of transcribed genes appears to be 30 to 40 % larger than in any other tissue (Cairney and Pullman 2007;Yakovlev et al 2014) with high relevance to the gene network in A. thaliana (300-450 genes, Cairney and Pullman 2007;Zhang et al 2012a). Transcript profiles during zygotic embryogenesis are highly correlated between Pinus pinaster and A. thaliana, with only 3 % of the transcripts estimated to be gymnosperm-specific (de Vega-Bartol et al 2013).…”

“…Transcript profiles during zygotic embryogenesis are highly correlated between Pinus pinaster and A. thaliana, with only 3 % of the transcripts estimated to be gymnosperm-specific (de Vega-Bartol et al 2013). Differences between angiosperms and gymnosperms are thought to arise principally from spatiotemporal variations in gene expression resulting partly from epigenetic modifications, which may act as an adaptive mechanism in such long-lived species (Cairney and Pullman 2007;Vestman et al 2011;de VegaBartol et al 2013). Yakovlev et al (2014) specifically reported temperature-dependent differential transcriptomes in Picea abies embryogenic masses potentially associated with the formation of an epigenetic memory, with a delayed, persistent impact on seedling growth.…”