Dissecting the cellular architecture and genetic circuitry of the soybean seed.

Seeds are complex structures composed of three regions, embryo, endosperm, and seed coat, with each further divided into subregions that consist of tissues, cell layers, and cell types. Although the seed is well characterized anatomically, much less is known about the genetic circuitry that dictates its spatial complexity. To address this issue, we profiled mRNAs from anatomically distinct seed subregions at several developmental stages.

Genome-wide profiling of soybean WRINKLED1 transcription factor binding sites provides insight into seed storage lipid biosynthesis.

Understanding the regulatory mechanisms controlling storage lipid accumulation will inform strategies to enhance seed oil quality and quantity in crop plants. The WRINKLED1 transcription factor (WRI1 TF) is a central regulator of lipid biosynthesis. We characterized the genome-wide binding profile of soybean (Gm)WRI1 and show that the TF directly regulates genes encoding numerous enzymes and proteins in the fatty acid and triacylglycerol biosynthetic pathways.

A reevaluation of the role of the trihelix transcription factors as repressors of the seed maturation program.

Developmental transitions are typically tightly controlled at the transcriptional level. Two of these transitions involve the induction of the embryo maturation program midway through seed development and its repression during the vegetative phase of plant growth. Very little is known about the factors responsible for this regulation during early embryogenesis, and only a couple of transcription factors have been characterized as repressors during the postgerminative phase.

Comparative analysis of embryo proper and suspensor transcriptomes in plant embryos with different morphologies.

An important question is what genes govern the differentiation of plant embryos into suspensor and embryo proper regions following fertilization and division of the zygote. We compared embryo proper and suspensor transcriptomes of four plants that vary in embryo morphology within the suspensor region. We determined that genes encoding enzymes in several metabolic pathways leading to the formation of hormones, such as gibberellic acid, and other metabolites are up-regulated in giant scarlet runner bean and common bean suspensors.

Combinatorial interactions of the LEC1 transcription factor specify diverse developmental programs during soybean seed development.

The LEAFY COTYLEDON1 (LEC1) transcription factor is a central regulator of seed development, because it controls diverse biological programs during seed development, such as embryo morphogenesis, photosynthesis, and seed maturation. To understand how LEC1 regulates different gene sets during development, we explored the possibility that LEC1 acts in combination with other transcription factors. We identified and compared genes that are directly transcriptionally regulated by ABA-RESPONSIVE ELEMENT BINDING PROTEIN3 (AREB3), BASIC LEUCINE ZIPPER67 (bZIP67), and ABA INSENSITIVE3 (ABI3) with those regulated by LEC1.

Central role of the LEAFY COTYLEDON1 transcription factor in seed development.

Seed development is a complex period of the flowering plant life cycle. After fertilization, the three main regions of the seed, embryo, endosperm and seed coat, undergo a series of developmental processes that result in the production of a mature seed that is developmentally arrested, desiccated, and metabolically quiescent. These processes are highly coordinated, both temporally and spatially, to ensure the proper growth and development of the seed.

Seed genome hypomethylated regions are enriched in transcription factor genes.

The precise mechanisms that control gene activity during seed development remain largely unknown. Previously, we showed that several genes essential for seed development, including those encoding storage proteins, fatty acid biosynthesis enzymes, and transcriptional regulators (e.g.

Similarity between soybean and seed methylomes and loss of non-CG methylation does not affect seed development.

We profiled soybean and methylomes from the globular stage through dormancy and germination to understand the role of methylation in seed formation. CHH methylation increases significantly during development throughout the entire seed, targets primarily transposable elements (TEs), is maintained during endoreduplication, and drops precipitously within the germinating seedling. By contrast, no significant global changes in CG- and CHG-context methylation occur during the same developmental period.

LEC1 sequentially regulates the transcription of genes involved in diverse developmental processes during seed development.

LEAFY COTYLEDON1 (LEC1), an atypical subunit of the nuclear transcription factor Y (NF-Y) CCAAT-binding transcription factor, is a central regulator that controls many aspects of seed development including the maturation phase during which seeds accumulate storage macromolecules and embryos acquire the ability to withstand desiccation. To define the gene networks and developmental processes controlled by LEC1, genes regulated directly by and downstream of LEC1 were identified. We compared the mRNA profiles of wild-type and -null mutant seeds at several stages of development to define genes that are down-regulated or up-regulated by the mutation.

A naïve Bayesian classifier for identifying plant microRNAs.

MicroRNAs (miRNAs) are important regulatory molecules in eukaryotic organisms. Existing methods for the identification of mature miRNA sequences in plants rely extensively on the search for stem-loop structures, leading to high false negative rates. Here, we describe a probabilistic method for ranking putative plant miRNAs using a naïve Bayes classifier and its publicly available implementation.

Light-Induced Indeterminacy Alters Shade-Avoiding Tomato Leaf Morphology.

Plants sense the foliar shade of competitors and alter their developmental programs through the shade-avoidance response. Internode and petiole elongation, and changes in overall leaf area and leaf mass per area, are the stereotypical architectural responses to foliar shade in the shoot. However, changes in leaf shape and complexity in response to shade remain incompletely, and qualitatively, described.

Down-Regulating the Expression of 53 Soybean Transcription Factor Genes Uncovers a Role for SPEECHLESS in Initiating Stomatal Cell Lineages during Embryo Development.

We used an RNA interference screen to assay the function of 53 transcription factor messenger RNAs (mRNAs) that accumulate specifically within soybean (Glycine max) seed regions, subregions, and tissues during development. We show that basic helix-loop-helix (bHLH) transcription factor genes represented by Glyma04g41710 and its paralogs are required for the formation of stoma in leaves and stomatal precursor complexes in mature embryo cotyledons. Phylogenetic analysis indicates that these bHLH transcription factor genes are orthologous to Arabidopsis (Arabidopsis thaliana) SPEECHLESS (SPCH) that initiate asymmetric cell divisions in the leaf protoderm layer and establish stomatal cell lineages.

Transcriptome atlas of the Arabidopsis funiculus--a study of maternal seed subregions.

The funiculus anchors the structurally complex seed to the maternal plant, and is the only direct route of transport for nutrients and maternal signals to the seed. While our understanding of seed development is becoming clearer, current understanding of the genetics and cellular mechanisms that contribute to funiculus development is limited. Using laser microdissection combined with global RNA-profiling experiments we compared the genetic profiles of all maternal and zygotic regions and subregions during seed development.

Genomic dissection of the seed.

Seeds play an integral role in the global food supply and account for more than 70% of the calories that we consume on a daily basis. To meet the demands of an increasing population, scientists are turning to seed genomics research to find new and innovative ways to increase food production. Seed genomics is evolving rapidly, and the information produced from seed genomics research has exploded over the past two decades.

AtRH57, a DEAD-box RNA helicase, is involved in feedback inhibition of glucose-mediated abscisic acid accumulation during seedling development and additively affects pre-ribosomal RNA processing with high glucose.

The Arabidopsis thaliana T-DNA insertion mutant rh57-1 exhibited hypersensitivity to glucose (Glc) and abscisic acid (ABA). The other two rh57 mutants also showed Glc hypersensitivity similar to rh57-1, strongly suggesting that the Glc-hypersensitive feature of these mutants results from mutation of AtRH57. rh57-1 and rh57-3 displayed severely impaired seedling growth when grown in Glc concentrations higher than 3%.

LEAFY COTYLEDON1, a key regulator of seed development, is expressed in vegetative and sexual propagules of Selaginella moellendorffii.

LEAFY COTYLEDON1 (LEC1) is a central regulator of seed development that plays a key role in controlling the maturation phase during which storage macromolecules accumulate and the embryo becomes tolerant of desiccation. We queried the genomes of seedless plants and identified a LEC1 homolog in the lycophyte, Selaginella moellendorffii, but not in the bryophyte, Physcomitrella patens. Genetic suppression experiments indicated that Selaginella LEC1 is the functional ortholog of Arabidopsis LEC1.

Comprehensive developmental profiles of gene activity in regions and subregions of the Arabidopsis seed.

Seeds are complex structures that consist of the embryo, endosperm, and seed-coat regions that are of different ontogenetic origins, and each region can be further divided into morphologically distinct subregions. Despite the importance of seeds for food, fiber, and fuel globally, little is known of the cellular processes that characterize each subregion or how these processes are integrated to permit the coordinated development of the seed. We profiled gene activity genome-wide in every organ, tissue, and cell type of Arabidopsis seeds from fertilization through maturity.

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.

Indispensable Roles of Plastids in Arabidopsis thaliana Embryogenesis.

The plastid is an organelle vital to all photosynthetic and some non-photosynthetic eukaryotes. In the model plant Arabidopsis thaliana, a number of nuclear genes encoding plastid proteins have been found to be necessary for embryo development. However, the exact roles of plastids in this process remain largely unknown.

Regulation of imprinted gene expression in Arabidopsis endosperm.

Imprinted genes are expressed primarily or exclusively from either the maternal or paternal allele, a phenomenon that occurs in flowering plants and mammals. Flowering plant imprinted gene expression has been described primarily in endosperm, a terminal nutritive tissue consumed by the embryo during seed development or after germination. Imprinted expression in Arabidopsis thaliana endosperm is orchestrated by differences in cytosine DNA methylation between the paternal and maternal genomes as well as by Polycomb group proteins.

Global analysis of gene activity during Arabidopsis seed development and identification of seed-specific transcription factors.

Most of the transcription factors (TFs) responsible for controlling seed development are not yet known. To identify TF genes expressed at specific stages of seed development, including those unique to seeds, we used Affymetrix GeneChips to profile Arabidopsis genes active in seeds from fertilization through maturation and at other times of the plant life cycle. Seed gene sets were compared with those expressed in prefertilization ovules, germinating seedlings, and leaves, roots, stems, and floral buds of the mature plant.

Effects of APETALA2 on embryo, endosperm, and seed coat development determine seed size in Arabidopsis.

Arabidopsis APETALA2 (AP2) controls seed mass maternally, with ap2 mutants producing larger seeds than wild type. Here, we show that AP2 influences development of the three major seed compartments: embryo, endosperm, and seed coat. AP2 appears to have a significant effect on endosperm development.

Arabidopsis homolog of the yeast TREX-2 mRNA export complex: components and anchoring nucleoporin.

Nuclear pore complexes (NPCs) are vital to nuclear-cytoplasmic communication in eukaryotes. The yeast NPC-associated TREX-2 complex, also known as the Thp1-Sac3-Cdc31-Sus1 complex, is anchored on the NPC via the nucleoporin Nup1, and is essential for mRNA export. Here we report the identification and characterization of the putative Arabidopsis thaliana TREX-2 complex and its anchoring nucleoporin.

LECs go crazy in embryo development.

Two fundamental aspects of plant development are the maturation phase of embryo development in seed plants and totipotency via somatic embryogenesis (SE). The LEAFY COTYLEDON (LEC) transcription factors (TFs) establish environments that promote cellular processes characteristic of the maturation phase and the initiation of somatic embryo formation. Based on recent studies, we and others propose that specific target genes activated by the LEC TFs underlie, in part, their roles in the maturation phase and SE.

The Arabidopsis BRAHMA chromatin-remodeling ATPase is involved in repression of seed maturation genes in leaves.

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.