Project description:The effectiveness of microspore embryogenesis and plant formation from in vitro cultivated microspores is determined by a complex network of internal and environmental factors. Plant breeding and genetic engineering widely use haploids/doubled haploids (DHs) derived from in vitro-cultured microspores, but the mechanism of ME induction remains poorly defined. Here, RNA-sequencing was used to characterize the transcriptional landscapes of four early stages of ME in two barley cultivars (Golden Promise and Igri) that are contrastingly responsive in the microspore-derived plant formation. Our experimental setup revealed fundamental regulatory networks, key marker genes of ME (628 stage-specific markers), and 160 candidate genes crucial for genotype-dependent responsiveness/resistance to ME. We found that transcription factors probably give rise to embryo-like structure and callus formation at stage III and determine their further development. Our high-resolution temporal transcriptome atlas provides an important resource for future functional studies aiming at unravelling the genetic control of microspore transition.
Project description:Somatic embryogenesis (SE), a morphogenic process that takes advantage of the regenerative potential of plants to replicate whole plants starting from somatic explants, can be a source of variation with potential applications in plant breeding. It is one of the most suitable tools to apply functional genomics studies and genetic improvement in plants. However, beyond a few pioneering works mainly focused on model plants, the molecular characterization of SE mechanisms is still elusive, especially for woody species. In grapevine, this process is affected by many factors such as explant type, culture conditions and, most importantly, genotype. Many cultivars, in fact, have shown recalcitrance to tissue culture and transformation, and very low SE competence. Thus, the understanding of SE competence behind the regenerative aptitude is fundamental to the widespread application of the so-called “next-generation breeding techniques”, such as cisgenesis and genome editing, in grapevine. Here, we explored genetic and epigenetic features of the SE process in grapevine by investigating the behavior of two genotypes showing opposite SE competence. Embryogenic tissues were induced from immature stamens excised from field-collected flower clusters of Sangiovese (highly competent for embryogenesis) and Cabernet Sauvignon (poorly competent for embryogenesis). A multilayered approach was used to profile mRNA, smallRNAs and methylated DNA with high-throughput sequencing technologies in the initial explants, on undifferentiated calli induced after 40 days of culture, and in embryogenic and non-embryogenic calli after 3 months of culture. A comprehensive comparison of transcriptomes of the different types of calli with the grapevine gene expression atlas revealed that, in grapevine, the dedifferentiation to the callus formation during the embryogenesis process occurs via a ‘berry’ developmental pathway. This is dissimilar from that shown in Arabidopsis, in which dedifferentiated calli are more similar to the tip of a root meristem. Interestingly, a Gene Ontology (GO) analysis revealed that secondary metabolism and gene expression regulation/epigenetics are the enriched functional categories of genes differentially down- and up-regulated in embryogenic vs non-embryogenic calli, respectively. These results prompted us to define the epigenetic landscape dynamics during SE in grapevine, revealing a significant increase in DNA methylation, especially in intergenic regions, in the embryogenic calli tissues. Finally, we proposed potential key regulators of SE in different genotypes that could represent putative targets of next-generation breeding techniques in grapevine.
Project description:Waterlogging leads to major crop losses globally, particularly for waterlogging sensitive crops such as barley. Waterlogging reduces oxygen availability and results in additional stresses, leading to the activation of hypoxia and stress response pathways that promote plant survival. Although certain barley varieties have been shown to be more tolerant to waterlogging than others and some tolerance-related QTLs have been identified, the molecular mechanisms underlying this trait are mostly unknown. Transcriptomics approaches can provide very valuable information for our understanding of waterlogging tolerance. Here, we surveyed 21 barley varieties for the differential transcriptional activation of conserved hypoxia-response genes under waterlogging, and selected five varieties with different levels of induction of core hypoxia-response genes. We further characterized their phenotypic response to waterlogging in terms of shoot and root traits. RNA-sequencing to evaluate the genome-wide transcriptional responses to waterlogging of these selected varieties led to the identification of a set of 98 waterlogging-response genes common to the different datasets. Many of these genes are orthologs of the so-called ‘core hypoxia response genes’, thus highlighting the conservation of plant responses to waterlogging. Hierarchical clustering analysis also identified groups of genes with intrinsic differential expression between varieties prior to waterlogging stress. These genes could constitute interesting candidates to study ‘predisposition’ to waterlogging tolerance or sensitivity in barley.
Project description:Somatic embryogenesis (SE), a morphogenic process that takes advantage of the regenerative potential of plants to replicate whole plants starting from somatic explants, can be a source of variation with potential applications in plant breeding. It is one of the most suitable tools to apply functional genomics studies and genetic improvement in plants. However, beyond a few pioneering works mainly focused on model plants, the molecular characterization of SE mechanisms is still elusive, especially for woody species. In grapevine, this process is affected by many factors such as explant type, culture conditions and, most importantly, genotype. Many cultivars, in fact, have shown recalcitrance to tissue culture and transformation, and very low SE competence. Thus, the understanding of SE competence behind the regenerative aptitude is fundamental to the widespread application of the so-called “next-generation breeding techniques”, such as cisgenesis and genome editing, in grapevine. Here, we explored genetic and epigenetic features of the SE process in grapevine by investigating the behavior of two genotypes showing opposite SE competence. Embryogenic tissues were induced from immature stamens excised from field-collected flower clusters of Sangiovese (highly competent for embryogenesis) and Cabernet Sauvignon (poorly competent for embryogenesis). A multilayered approach was used to profile mRNA, smallRNAs and methylated DNA with high-throughput sequencing technologies in the initial explants, on undifferentiated calli induced after 40 days of culture, and in embryogenic and non-embryogenic calli after 3 months of culture. A comprehensive comparison of transcriptomes of the different types of calli with the grapevine gene expression atlas revealed that, in grapevine, the dedifferentiation to the callus formation during the embryogenesis process occurs via a ‘berry’ developmental pathway. This is dissimilar from that shown in Arabidopsis, in which dedifferentiated calli are more similar to the tip of a root meristem. Interestingly, a Gene Ontology (GO) analysis revealed that secondary metabolism and gene expression regulation/epigenetics are the enriched functional categories of genes differentially down- and up-regulated in embryogenic vs non-embryogenic calli, respectively. These results prompted us to define the epigenetic landscape dynamics during SE in grapevine, revealing a significant increase in DNA methylation, especially in intergenic regions, in the embryogenic calli tissues. Finally, we proposed potential key regulators of SE in different genotypes that could represent putative targets of next-generation breeding techniques in grapevine.
Project description:Transcript levels of barley genes were examined in the wheat-barley chromosome addition lines having one of six barley chromomes, 2H, 3H, 4H, 5H, 6H and 7H. ****[PLEXdb(http://www.plexdb.org) has submitted this series at GEO on behalf of the original contributor, Seungho Cho. The equivalent experiment is BB8 at PLEXdb.]