Synergistic repression of the embryonic programme by SET DOMAIN GROUP 8 and EMBRYONIC FLOWER 2 in Arabidopsis seedlings

The seed maturation programme occurs only during the late phase of embryo development, and repression of the maturation genes is pivotal for seedling development. However, mechanisms that repress the expression of this programme in vegetative tissues are not well understood. A genetic screen was performed for mutants that express maturation genes in leaves. Here, it is shown that mutations affecting SDG8 (SET DOMAIN GROUP 8), a putative histone methyltransferase, cause ectopic expression of a subset of maturation genes in leaves. Further, to investigate the relationship between SDG8 and the Polycomb Group (PcG) proteins, which are known to repress many developmentally important genes including seed maturation genes, double mutants were made and formation of somatic embryos was observed on mutant seedlings with mutations in both SDG8 and EMF2 (EMBRYONIC FLOWER 2). Analysis of histone methylation status at the chromatin sites of a number of maturation loci revealed a synergistic effect of emf2 and sdg8 on the deposition of the active histone mark which is the trimethylation of Lys4 on histone 3 (H3K4me3). This is consistent with high expression of these genes and formation of somatic embryos in the emf2 sdg8 double mutants. Interestingly, a double mutant of sdg8 and vrn2 (vernalization2), a paralogue of EMF2, grew and developed normally to maturity. These observations demonstrate a functional cooperative interplay between SDG8 and an EMF2-containing PcG complex in maintaining vegetative cell identity by repressing seed genes to promote seedling development. The work also indicates the functional specificities of PcG complexes in Arabidopsis

Economic Analysis of Knowledge: The History of Thought and the Central Themes

Following the development of knowledge economies, there has been a rapid expansion of economic analysis of knowledge, both in the context of technological knowledge in particular and the decision theory in general. This paper surveys this literature by identifying the main themes and contributions and outlines the future prospects of the discipline. The wide scope of knowledge related questions in terms of applicability and alternative approaches has led to the fragmentation of research. Nevertheless, one can identify a continuing tradition which analyses various aspects of the generation, dissemination and use of knowledge in the economy

Minimum Information about a Biosynthetic Gene cluster

A wide variety of enzymatic pathways that produce specialized metabolites in bacteria, fungi and plants are known to be encoded in biosynthetic gene clusters. Information about these clusters, pathways and metabolites is currently dispersed throughout the literature, making it difficult to exploit. To facilitate consistent and systematic deposition and retrieval of data on biosynthetic gene clusters, we propose the Minimum Information about a Biosynthetic Gene cluster (MIBiG) data standard.Chemistry and Chemical Biolog

Cloning of Brassica napus phospholipase C2 (BnPLC2), phosphatidylinositol 3-kinase (BnVPS34) and phosphatidylinositol synthase1 (BnPtdlns S1)--comparative analysis of the effect of abiotic stresses on the expression of phosphatidylinositol signal transduction-related genes in B. napus

NRC publication: Ye

Two naturally occurring deletion mutants of 12S seed storage proteins in Arabidopsis thaliana

NRC publication: Ye

Transcriptome profiling and methyl homeostasis of an Arabidopsis mutant deficient in S-adenosylhomocysteine hydrolase1 (SAHH1)

Transcriptome profiling was conducted to detect genes whose expression is significantly changed in an Arabidopsis mutant deficient in S-adenosylhomocysteine hydrolase1 (SAHH1) during early seedling development when mutant phenotypes could be clearly observed. A total of 2,040 differentially expressed genes were identified, representing approximately 6.7 % of the 30,385 DNA oligonucleotide targets on the microarray. Among these differential expressed genes, many were mapped to pathways essential to plant growth and development including those of primary, secondary and hormone metabolisms. A significant proportion of up-regulated genes encoded transposable elements which were mapped to the centromeric and pericentromeric regions of the Arabidopsis chromosomes that were analyzed. A number of down-regulated genes were found to be involved in root hair formation, which might have contributed to the root hair defective phenotype of the mutant. Analysis of genes encoding transposable elements and those associating with root hair development indicated that these genes were highly co-expressed during seedling development. Despite SAHH1 deficiency, the expression of genes encoding methyltransferase remained largely unchanged in the sahh1 mutant. Bisulfite sequencing analysis of the transposable elements and the FWA gene revealed that their sequences in the mutant were deficient of 5-methylcytosines. Analysis of mutant genomic DNA using restriction endonucleases that were unable to cut methylated DNA suggested a genome-wide hypomethylation had occurred in the mutant. These results indicated that SAHH1 plays a critical role in methyl homeostasis, and its deficiency is a major contributing factor to the change of global gene expression, metabolic pathways and activation of transposable elements in the sahh1 mutant.Peer reviewed: YesNRC publication: Ye

The Arabidopsis BRAHMA Chromatin-Remodeling ATPase Is Involved in Repression of Seed Maturation Genes in Leaves1[W][OA]

Synthesis and accumulation of seed storage proteins (SSPs) is an important aspect of the seed maturation program. Genes encoding SSPs are specifically and highly expressed in the seed during maturation. However, the mechanisms that repress the expression of these genes in leaf tissue are not well understood. To gain insight into the repression mechanisms, we performed a genetic screen for mutants that express SSPs in leaves. Here, we show that mutations affecting BRAHMA (BRM), a SNF2 chromatin-remodeling ATPase, cause ectopic expression of a subset of SSPs and other embryogenesis-related genes in leaf tissue. Consistent with the notion that such SNF2-like ATPases form protein complexes in vivo, we observed similar phenotypes for mutations of AtSWI3C, a BRM-interacting partner, and BSH, a SNF5 homolog and essential SWI/SNF subunit. Chromatin immunoprecipitation experiments show that BRM is recruited to the promoters of a number of embryogenesis genes in wild-type leaves, including the 2S genes, expressed in brm leaves. Consistent with its role in nucleosome remodeling, BRM appears to affect the chromatin structure of the At2S2 promoter. Thus, the BRM-containing chromatin-remodeling ATPase complex involved in many aspects of plant development mediates the repression of SSPs in leaf tissue

Improving euricic acid content in rapeseed through biotechnology: what can the Arabidopsis FAE1 and the Yeast SLC1-1 genes contribute

The main goal of our research is to produce, by genetic manipulation, Brassica napus L. cultivars with higher amounts of 22:1 in their seed oil than in present Canadian high erucic acid rapeseed (HEAR) cultivars developed through traditional breeding, ideally with proportions of 22:1 approaching 80 mol% (828 g kg\u207b\ub9). To probe some rate-limiting steps in the accumulation of triacylglycerols containing very long chain fatty acids (VLCFAs), particularly erucic acid (22:1), we have taken a transgenic approach, studying the effect of expressing two target genes in HEAR B. napus cv. Hero. To study the role of the elongase complex, involved in elongation of C18 fatty acid moieties to produce VLCFAs, we expressed the Arabidopsis thaliana L., fatty acid elongase 1 (FAE1) gene under the control of a seed-specific promoter (napin), in Hero. This resulted in increased proportions of 22:1 in the seed oil, rising from 430 g kg\u207b\ub9 in non-transformed controls to 480 to 530 g kg\u207b\ub9 22:1 in FAE1 transgenic Hero lines. The FAE1 lines exhibited higher elongase activity in vitro compared to control lines. These data suggest that the level of active condensing enzyme in the native elongase complex is somewhat rate limiting for synthesis of erucic acid and other VLCFAs in HEAR. In small scale field trials, the VLCFA and 22:1 content of FAE1 transgenic lines were superior to field-grown control lines. We report that in field plot trials, the progeny of our best T4 B. napus cv. Hero SLC1-1 transgenic lines clearly out-performed controls in terms of 22:1, oil content, and yield.Peer reviewed: YesNRC publication: Ye

Brassica carinata-A New Molecular Farming Platform for Delivering Bio-industrial Oil Feedstocks: Case studies of Genetic Modifications to Improve Seed Very Long-Chain Fatty Acid and Oil Content in Seeds

Crop development and species diversity are important aspects of the emerging global bioeconomy, as is maximizing crop value through total crop utilization. We advocate development of Brassica carinata as a biorefinery and bioindustrial oils platform using traditional and molecular breeding techniques and tools. We review genetic studies and breeding efforts to develop elite B. carinata germplasm, work involving development of transformation and regeneration protocols, target gene isolation, and transgene expression. Genetic modification strategies using a B. carinata breeding line as a delivery platform for very long-chain fatty acid-enhanced/modified oils are presented as case studies. The target oil products are erucic acid (22:1 \u39413), docosadienoic acid (22:2 \u3945, \u39413) and nervonic acid (24:1 \u39415); in addition transgenic efforts to enhance B. carinata seed oil content are discussed. The overall advantages and current limitations to utilizing this crop are delineated. Other anticipated biobased products from a B. carinata platform may include, but are not limited to, the production of biolubricants, biofuels and biopolymers from the oil, biopesticides, antioxidants, as well as plant gums, and vegetable protein-based bioplastics and novel food and feed products. In summation, this collaborative B. carinata breeding/germplasm development/value-added molecular modification effort will not only contribute to the development of renewable feedstocks for the emerging Canadian bioeconomy (biorefinery/bioproducts), but also promises to generate positive economic and environmental benefits.Peer reviewed: YesNRC publication: Ye

Metabolic engineering of brassica seeds oils: improvement of oil quality and quantity and alteration of carbon flux

NRC publication: Ye