Project description:Cellular differentiation is associated with changes in transcript populations. Accurate quantification of transcriptomes during development can thus provide global insights into differentiation processes including the fundamental specification and differentiation events operating during plant embryogenesis. However, multiple technical challenges have limited the ability to obtain high quality early embryonic transcriptomes, namely the low amount of RNA obtainable and contamination from surrounding endosperm and seed-coat tissues. We compared the performance of three low-input mRNA sequencing (mRNA-seq) library preparation kits on 0.1 to 5 nanograms (ng) of total RNA isolated from Arabidopsis thaliana (Arabidopsis) embryos and identified a low-cost method with superior performance. This mRNA-seq method was then used to profile the transcriptomes of Arabidopsis embryos across eight developmental stages. By comprehensively comparing embryonic and post-embryonic transcriptomes, we found that embryonic transcriptomes do not resemble any other plant tissue we analyzed. Moreover, transcriptome clustering analyses revealed the presence of four distinct phases of embryogenesis which are enriched in specific biological processes. We also compared zygotic embryo transcriptomes with publicly available somatic embryo transcriptomes. Strikingly, we found little resemblance between zygotic embryos and somatic embryos derived from late-staged zygotic embryos suggesting that somatic and zygotic embryo transcriptomes are distinct from each other. In addition to the biological insights gained from our systematic characterization of the Arabidopsis embryonic transcriptome, we provide a data-rich resource for the community to explore.
Project description:After fertilization, a plant's life relies on progression through embryogenesis and maintenance of the stem cell niches from which all post-embryonic organs arise. BABY BOOM (BBM) and other members of the AINTEGUMENTA-LIKE (AIL)/PLETHORA (PLT) clade of the AP2-type transcription factor family play important roles controlling these processes in Arabidopsis thaliana (Arabidopsis). Development of the plt2/bbm double mutant is blocked at during early embryogenesis (Galinha et al., 2007), and combinations of bbm with plt1 and plt3 lead to short roots as a result of meristem differentiation. In contrast, overexpression of BBM in Arabidopsis seedlings induces the formation of somatic embryos on cotyledons and leaves (Boutilier, 2002), showing that BBM is a key regulator of cell identity and proliferation. Although the functions of BBM and other AIL genes have been well described, the molecular mode of action of these transcription factors has not been well examined (reviewed in Horstman et al., 2013). Our previous study provided the first insight into BBM molecular function by identifying BBM targets through a microarray-based approach (Passarinho, 2008), but only a few BBM targets have been functionally characterized. To obtain a better understanding of BBM function, we identified direct BBM targets using a chromatin immunoprecipitation (ChIP) combined with massively-parallel DNA sequencing (ChIP-seq) approach. Somatic embryo tissue was used for the ChIP-seq experiments with the native BBM promoter (pBBM::BBM-YFP), with a line expressing nuclear-localized GFP from the same BBM promoter (pBBM::NLS-GFP) as a negative control. Whole, embryogenic seedlings of the 35S::BBM-GFP line were used for the 35S::BBM-GFP ChIP-seq experiments, with 35S::BBM embryogenic seedlings serving as a negative control. Both experiments were performed once, making a total of 4 samples.
Project description:After fertilization, a plant's life relies on progression through embryogenesis and maintenance of the stem cell niches from which all post-embryonic organs arise. BABY BOOM (BBM) and other members of the AINTEGUMENTA-LIKE (AIL)/PLETHORA (PLT) clade of the AP2-type transcription factor family play important roles controlling these processes in Arabidopsis thaliana (Arabidopsis). Development of the plt2/bbm double mutant is blocked at during early embryogenesis (Galinha et al., 2007), and combinations of bbm with plt1 and plt3 lead to short roots as a result of meristem differentiation. In contrast, overexpression of BBM in Arabidopsis seedlings induces the formation of somatic embryos on cotyledons and leaves (Boutilier, 2002), showing that BBM is a key regulator of cell identity and proliferation. Although the functions of BBM and other AIL genes have been well described, the molecular mode of action of these transcription factors has not been well examined (reviewed in Horstman et al., 2013). Our previous study provided the first insight into BBM molecular function by identifying BBM targets through a microarray-based approach (Passarinho, 2008), but only a few BBM targets have been functionally characterized. To obtain a better understanding of BBM function, we identified direct BBM targets using a chromatin immunoprecipitation (ChIP) combined with massively-parallel DNA sequencing (ChIP-seq) approach.