Arabidopsis Gynoecium Development – Reproductive competence of flowering plants requires proper development of the carpel, which is the female reproductive organ of the plant. The meristematic regions along the margin of the developing carpel generate ovules that will later develop into seeds. These meristematic regions have been termed carpel margin meristems (CMMs) and are functionally analogous to the mammalian ovary and placenta. The CMMs provide an excellent system to study basic problems in developmental biology such as patterning, the regulation of cellular proliferation and the control of organ size and shape. Dr. Franks’ research program seeks to clarify basic mechanisms of organ size and shape regulation and understand relationships between patterning cues and cellular proliferation within the carpel. Current research focuses on (1) the elucidation of the transcriptional gene regulatory network that controls ovule initiation and meristematic competence in the carpel; 2) the identification and functional studies of novel genes that play a critical role in CMM development; 3) the application of fluorescent activated cell sorting (FACS) technology to isolate transcriptionally-distinct populations of carpel cell types.
Hybrid Seed Inviability and the Evolution of Endosperm Development in Mimulus – The endosperm is the starch- and/or protein-rich tissue within the seed. It is estimated that 67% of the calories of the human diet are derived from the endosperm of agricultural varieties (mostly grains). In addition to its agricultural importance, the study of embryo and endosperm development is of interest to both developmental biologists and evolutionary biologists. The parental conflict theory is an evolutionary theory that predicts that genes supporting endosperm and embryo development will be subject to imprinting and parent-of-origin effects. Furthermore, the rapid evolution of genes that function in the regulation of parental conflict has been proposed to act as a reproductive isolation mechanism and thus may support speciation events. In this collaboration with Dr. John Willis in the Dept. of Biology at Duke University, we are examining embryo and endosperm developmental defects resulting from incompatible inter-specific crosses between Mimulusspecies. We expect these studies will illuminate developmental, molecular and evolutionary mechanisms of reproductive isolation and speciation, as well as mechanisms of endosperm development.
- GN 434 (spring)
Area(s) of Expertise
Molecular Genetics of Plant Development
- Functional characterization of Terminal Flower1 homolog in Cornus canadensis by genetic transformation , Plant Cell Reports (2019)
- Alterations of CorTFL1 and CorAP1 expression correlate with major evolutionary shifts of inflorescence architecture in Cornus (Cornaceae) – a proposed model for variation of closed inflorescence forms , New Phytologist (2017)
- Redundant cArG box cis-motif activity mediates SHATTERPROOF2 transcriptional regulation during arabidopsis thaliana gynoecium development , Frontiers in Plant Science (2017)
- Analysis of two TFL1 homologs of dogwood species (Cornus L.) indicates functional conservation in control of transition to flowering. , Planta (2016)
- Disruption of endosperm development is a major cause of hybrid seed inviability between Mimulus guttatus and Mimulus nudatus. , New Phytologist (2016)
- Histological Analysis of the Arabidopsis Gynoecium and Ovules Using Chloral Hydrate Clearing and Differential Interference Contrast Light Microscopy. , Methods in Molecular Biology (2016)
- SEUSS integrates gibberellin signaling with transcriptional inputs from the SHR-SCR-SCL3 module to regulate middle cortex formation in the Arabidopsis root. , Plant Physiology (2016)
- Transcriptomic Signature of the SHATTERPROOF2 Expression Domain Reveals the Meristematic Nature of Arabidopsis Gynoecial Medial Domain. , Plant Physiology (2016)
- Auxin and cytokinin act during gynoecial patterning and the development of ovules from the meristematic medial domain , Wiley Interdisciplinary Reviews: Developmental Biology (2015)
- Molecular basis of fruit development , Frontiers in Plant Science (2015)
We are using the diversity of Mimulus (Monkey Flower) species to identify the molecular mechanisms of reproductive isolation and speciation. Our work will significantly contribute of our understanding of the molecular, ecological and evolutionary bases of speciation and biodiversity generation.
Enabling the next generation of sustainable farms requires a paradigm shift in resource management of the two most critical agricultural inputs for food production: water and nitrogen (N) - based fertilizer. Inefficient management of these resources increases food production costs, decreases productivity, and impacts the environment. An integrated approach is needed to improve the sustainability and efficiency throughout the production chain. Emerging (bio)electrochemical (BEC) technologies offer alternatives to conventional, fossil-fuel intensive N fertilizer production. Recently our team has demonstrated two game-changing BEC technologies: 1) microbial conversion of nitrogen gas into ammonium, and 2) plasma generation of N species (e.g., nitrate, nitrite) and other reactive species in water for fertilization and anti-pathogen benefits. We will integrate these technologies to produce BEC, N-based fertilizer, and with advanced sensor and delivery systems, we will precisely supply fertilizers for sustainable precision agriculture. Our proposed approach focuses on the development of a novel â€œBEC fertigation on demand systemâ€ by using sensor-driven data and molecular analyses to investigate BEC fertigation impact on the plantsâ€™ growth, adaptation, and microbiome; its impact on food safety and quality, and its economic feasibility for on-farm deployment.
Here we propose to determine the evolutionary genetic basis underlying species divergence in endosperm development and embryogenesis and their consequences for hybrid seed lethality, a principal isolating barrier in the Mimulus guttatus sp. complex . We focus on two diploid species, the serpentine endemic M. nudatus and the widespread M. guttatus, which do not hybridize in the wild despite their coexistence and shared pollinators. Controlled interspecific crosses yield two hybrid seed types: hybrid seed that exhibit early arrested endosperm development and hybrid seed with relatively normal early endosperm development but late endosperm deficiency. We integrate molecular and developmental experiments, RNA sequencing, and high-throughput genome mapping to elucidate the genetic mechanisms contributing to seed abortion in M. guttatus x M. nudatus crosses.
The coordination of spatial patterning cues and cellular proliferation underlies diverse processes from cancerous growth to reproductive development. A long-term objective of my research program is to understand how proliferative cues are coordinated with spatial information during organogenesis. In Arabidopsis thaliana this coordination of patterning and proliferation is necessary within the carpel margin meristem (CMM) to generate ovules that when fertilized will become seeds. In the previous funding period we demonstrated that the SEUSS (SEU) and AINTEGUMENTA (ANT) transcription factors regulate critical patterning events that support carpel margin meristem and ovule development. Our genetic analysis demonstrates that SEU and ANT share a partially redundant and overlapping function essential for proper seed formation. As SEU and ANT do not share sequence similarity, the molecular basis for this redundancy is not understood. We propose that the SEU and ANT activities synergistically converge at key transcriptional nodes. A node in this sense is a gene or a set of related genes that requires the combined activities of SEU and ANT for its expression. Our recently published transcriptomic analysis indicates that many of these nodes encode known transcriptional regulators. By studying these nodes we hope to better understand the transcriptional hierarchies that control CMM development and uncover the mechanistic basis of the synergistic action of SEU and ANT. Our transcriptomics study cannot determine if the nodes that we have identified are directly or indirectly regulated by SEU or ANT activity, However, even if these genes are indirectly controlled by SEU and ANT activity, their expression within the developing CMM suggests they may still play a critical functional role during CMM development. Furthermore, having now identified a set of genes that are enriched for CMM expression we are in a position to study the cis-regulatory elements that support gene expression within the CMM and medial gynoecial domain. Thus here we propose to: 1) Identify direct targets of SEU regulation within the CMM to further refine the transcriptional hierarchy required for CMM development; 2) assay the functional role of two of these nodes during CMM development; one encoded by the transcription factor PERIANTHIA and the second encoded by members of the REM family of B3 domain-containing proteins; 3) Identify cis-acting DNA regulatory elements required for CMM expression. Scientific significance: Understanding the coordination of cellular proliferation and spatial patterning during organogenesis is broadly of interest to scientists working in a diversity of fields. Completion of these specific aims will move us toward this future goal by illuminating the mechanistic basis for the overlapping functions of SEU and ANT during carpel margin and ovule development. Additionally, we expect that by elucidating the molecular mechanisms of the synergistic action of SEU and ANT upon key transcriptional nodes, we will engender a greater understanding of the molecular underpinnings of non-additivity within transcriptional networks and the complexity of developmental programs. Past NSF funding for this project (IOS-0821896) has resulted in the publication of five articles in well-respected journals (two in Plant Physiology, and one each in Developmental Biology, PLoS One, and BMC Plant Biology). Broader impacts: I ensure a broad societal impact from my program by integrating my research efforts with my teaching and training responsibilities and by widely disseminating materials and results. Furthermore, I initiated and continue to lead an outreach group that prepares and presents hands-on science demonstrations at local North Carolina schools. Our group has reached over 1500 Kindergarten through Grade 12 students over the past six years and continues to develop new demonstration modules inspired by our current work in developmental biology and genetics.
Variation in floral display (inflorescence) affects the success of plant reproduction and the yield of a crop by influencing seed number and dispersal/harvest ability. Despite its importance, little progress has been made in understanding how developmental and genetic changes have shaped inflorescence architectures in angiosperm evolution, in part because existing model organisms exhibit little variation in these traits. Species of Dogwood (Cornus L.) are popular ornamental trees in American landscapes due to their spectacular inflorescences often associated with large showy (petaloid) bracts. The genus offers us a unique opportunity to tackle this important problem. Cornus exhibits a wide variation in inflorescence structure, including heads, umbels and compound cymes. A recent breakthrough in our laboratory has resulted in successful regeneration and transformation of a key species of the genus. This new ability along with our recent achievements in phylogenetic reconstruction and nearly completed comparative developmental studies, now provides a timely opportunity to develop a model for investigating the molecular mechanisms shaping inflorescence architectures in a non-model plant lineage. In this proposal, we aim to test four hypotheses to gain insights into the changes in developmental and genetic mechanisms that may have led to alteration of inflorescence forms in dogwoods. Hypotheses: 1. Differences in early development processes lay the ground for divergence of inflorescence architectures in dogwood species. 2. Spatial, temporal, and quantitative variation of expression of conserved key inflorescence regulatory genes are essential for the changes of inflorescence architecture. 3. Expression of petal identity genes in bracts is essential for the origin of the petaloidy of bracts in dogwoods. 4. Spatial, temporal, and quantitative variation of expression of other genes are essential for the modification of inflorescence architecture and origin of petaloid bracts in dogwoods. Objectives: 1. Complete the comparative developmental characterization of four Cornus inflorescence types. 2. Comparative characterization of the expression of conserved key inflorescence regulators and petal identity genes in different inflorescence types. 3. Identify new genes regulating inflorescence development and bract petaloidy in dogwood. 4. Optimize the existing transformation system of Cornus canadensis and test the function of conserved key inflorescence regulatory genes Intellectual merits: This project represents the first study investigating the molecular controls of inflorescence development and evolution using a comparative approach on multiple closely related woody species from a non-model plant lineage. Although the proposal has technical challenges, we have overcome the most significant hurdles and achieving of our objectives would offer novel insights into the genetic basis underlying the evolutionary transitions of floral display strategies, of which the knowledge is presently lacking. The transformation system has tremendous potentials for future research of genetic controls of other plant traits including resistance to fungal diseases and drought, and flowering time divergence among species. By providing a transformation system in a non-model plant, this study will potentially provide a new tool for genetic analysis in other plants that are more closely related to the dogwoods than to the few existing model species. Broader impact: The project will not only enhance our understanding of inflorescence development and evolution in angiosperms, but also hold promise in breeding and bioengineering of dogwoods. Biotechnological improvement of Cornus species in display, disease and drought resistance holds tremendous industrial potential. Thus the results of this project will have broad interests to the scientific, biotechnolgical, and industrial communities. Perfection of the transformation system will immediately benefit the research of identifying genes resistant to the dogwood anthracnose disease that