Potential for urban agriculture to support accessible and impactful undergraduate biology education.

Active learning in STEM education is essential for engaging the diverse pool of scholars needed to address pressing environmental and social challenges. However, active learning formats are difficult to scale and their incorporation into STEM teaching at U.S. universities varies widely. Here, we argue that urban agriculture as a theme can significantly increase active learning in undergraduate biology education by facilitating outdoor fieldwork and community-engaged education. We begin by reviewing benefits of field courses and community engagement activities for undergraduate biology and discuss constraints to their broader implementation. We then describe how urban agriculture can connect biology concepts to pressing global changes, provide field research opportunities, and connect students to communities. Next, we assess the extent to which urban agriculture and related themes have already been incorporated into biology-related programs in the United States using a review of major programs, reports on how campus gardens are used, and case studies from five higher education institutions (HEIs) engaging with this issue. We found that while field experiences are fairly common in major biology programs, community engagement opportunities are rare, and urban agriculture is almost nonexistent in course descriptions. We also found that many U.S. HEIs have campus gardens, but evidence suggests that they are rarely used in biology courses. Finally, case studies of five HEIs highlight innovative programming but also significant opportunities for further implementation. Together, our results suggest that urban agriculture is rarely incorporated into undergraduate biology in the United States, but there are significant prospects for doing so. We end with recommendations for integrating urban agriculture into undergraduate biology, including the development of campus gardens, research programs, community engagement partnerships, and collaborative networks. If done with care, this integration could help students make community contributions within required coursework, and help instructors feel a greater sense of accomplishment in an era of uncertainty.

Genetic diversity of Chamaecrista fasciculata (Fabaceae) from the USDA germplasm collection.

OBJECTIVE: Chamaecrista fasciculata is a widespread annual legume across Eastern North America, with potential as a restoration planting, biofuel crop, and genetic model for non-papillinoid legumes. As a non-Papilinoid, C. fasciculata, belongs to the Caesalpiniod group in which nodulation likely arose independently of the nodulation in Papilinoid and Mimosoid legumes. Thus, C. fasciculata is an attractive model system for legume evolution. In this study, we describe population structure and genetic diversity among 32 USDA germplasm accessions of C. fasciculata using 317 AFLP markers developed from 12 primer pairs, to assess where geographically there is the most genetic variation. RESULTS: We found that the C. fasciculata germplasm collection fall into four clusters with admixture among them. After correcting for outliers, our analysis shows two primary groups across Eastern and Central North America. To better understand the population biology of this species, further sampling of the full range of this widespread species is needed across North America, as well as the development of a larger set of markers providing denser coverage of the genome. Further sampling will help clarify geographical relationships in this widespread temperate species.

From the NSF: The National Science Foundation's Investments in Broadening Participation in Science, Technology, Engineering, and Mathematics Education through Research and Capacity Building.

The National Science Foundation (NSF) has a long history of investment in broadening participation (BP) in science, technology, engineering, and mathematics (STEM) education. A review of past NSF BP efforts provides insights into how the portfolio of programs and activities has evolved and the broad array of innovative strategies that has been used to increase the participation of groups underrepresented in STEM, including women, minorities, and persons with disabilities. While many are familiar with these long-standing programmatic efforts, BP is also a key component of NSF's strategic plans, has been highlighted in National Science Board reports, and is the focus of ongoing outreach efforts. The majority of familiar BP programs, such as the Louis Stokes Alliances for Minority Participation (now 25 years old), are housed in the Directorate for Education and Human Resources. However, fellowship programs such as the Graduate Research Fellowships and Postdoctoral Research Fellowships under the Directorate for Biological Sciences (and parallel directorates in other STEM disciplines) are frequently used to address underrepresentation in STEM disciplines. The FY2016 and FY2017 budget requests incorporate funding for NSF INCLUDES, a new cross-agency BP initiative that will build on prior successes while addressing national BP challenges. NSF INCLUDES invites the use of innovative approaches for taking evidence-based best practices to scale, ushering in a new era in NSF BP advancement.

Making maxillary barbels with a proximal-distal gradient of Wnt signals in matrix-bound mesenchymal cells.

The evolution of specific appendages is made possible by the ontogenetic deployment of general cell signaling pathways. Many fishes, amphibians and reptiles have unique skin appendages known as barbels, which are poorly understood at the cellular and molecular level. In this study, we examine the cell arrangements, cell division patterns, and gene expression profiles associated with the zebrafish maxillary barbel, or ZMB. The earliest cellular organization of the ZMB is an internal whorl of mesenchymal cells in the dermis of the maxilla; there is no epithelial placode, nor any axially-elongated epithelial cells as expected of an apical ectodermal ridge (AER). As the ZMB develops, cells in S-phase are at first distributed randomly throughout the appendage, gradually transitioning to a proliferative population concentrated at the distal end. By observing ZMB ontogenetic stages in a Wnt-responsive transgenic reporter line, TCFsiam, we identified a strongly fluorescent mesenchymal cell layer within these developing appendages. Using an in vitro explant culture technique on developing barbel tissues, we co-localized the fluorescent label in these cells with the mitotic marker EdU. Surprisingly, the labeled cells showed little proliferation, indicating a slow-cycling subpopulation. Transmission electron microscopy of the ZMB located these cells in a single, circumferential layer within the barbel's matrix core. Morphologically, these cells resemble fibroblasts or osteoblasts; in addition to their matrix-bound location, they are identified by their pancake-shaped nuclei, abundant rough endoplasmic reticulum, and cytoplasmic extensions into the surrounding extracellular matrix. Taken together, these features define a novel mesenchymal cell population in zebrafish, the "TCF(+) core cells." A working model of barbel development is proposed, in which these minimally mitotic mesodermal cells produce collagenous matrix in response to ectodermally-derived Wnt signals deployed in a proximal-distal gradient along the appendage. This documents a novel mechanism of vertebrate appendage outgrowth. Similar genetic signals and cell behaviors may be responsible for the independent and repeated evolution of barbel structures in other fish species.

Polyploidy did not predate the evolution of nodulation in all legumes.

BACKGROUND: Several lines of evidence indicate that polyploidy occurred by around 54 million years ago, early in the history of legume evolution, but it has not been known whether this event was confined to the papilionoid subfamily (Papilionoideae; e.g. beans, medics, lupins) or occurred earlier. Determining the timing of the polyploidy event is important for understanding whether polyploidy might have contributed to rapid diversification and radiation of the legumes near the origin of the family; and whether polyploidy might have provided genetic material that enabled the evolution of a novel organ, the nitrogen-fixing nodule. Although symbioses with nitrogen-fixing partners have evolved in several lineages in the rosid I clade, nodules are widespread only in legume taxa, being nearly universal in the papilionoids and in the mimosoid subfamily (e.g., mimosas, acacias)--which diverged from the papilionoid legumes around 58 million years ago, soon after the origin of the legumes. METHODOLOGY/PRINCIPAL FINDINGS: Using transcriptome sequence data from Chamaecrista fasciculata, a nodulating member of the mimosoid clade, we tested whether this species underwent polyploidy within the timeframe of legume diversification. Analysis of gene family branching orders and synonymous-site divergence data from C. fasciculata, Glycine max (soybean), Medicago truncatula, and Vitis vinifera (grape; an outgroup to the rosid taxa) establish that the polyploidy event known from soybean and Medicago occurred after the separation of the mimosoid and papilionoid clades, and at or shortly before the Papilionoideae radiation. CONCLUSIONS: The ancestral legume genome was not fundamentally polyploid. Moreover, because there has not been an independent instance of polyploidy in the Chamaecrista lineage there is no necessary connection between polyploidy and nodulation in legumes. Chamaecrista may serve as a useful model in the legumes that lacks a paleopolyploid history, at least relative to the widely studied papilionoid models.

Biología del desarrollo

Principios de la biología del desarrollo. Biología del desarrollo: la tradición anatómica. Ciclos de vida y la evolución de los patrones de desarrollo. Principios de embriología experimental. La base genética del desarrollo. Comunicación en el desarrollo. Desarrollo embrionario temprano. Fecundación: el comienzo de un nuevo paradigma. Desarrollo temprano en invertebrados seleccionados. La genética de especificacioón del eje en drosophila. Desarrollo temprano y formación del eje en anfibios. Desarrollo temprano en los vertebrados: peces, aves y mamíferos. Desarrollo embrionario tardío. El surgimiento del extodermo: el sistema nervioso central y la epidermis. Células de la cresta neural y especificidad axonal. Mesodermo paraxial e intermedio. Lámina del mesodermo lateral y endodermo. Desarrollo de la extremidad de los tetrápodos. Determinación del sexo. Metamorfosis, regeneración y envejecimiento. La safa de la línea germinal. Ramificaciones adicionales de la biología del desarrollo. Una perspectiva general sobre el desarrollo de las plantas. Implicaciones médicas de la biología del desarrollo. regulación ambiental del desarrollo animal. Mecanismos de desarrollo del cambio evolutivo

Biología del desarrollo

Principios de la biología del desarrollo. Biología del desarrollo: la tradición anatómica. Ciclos de vida y la evolución de los patrones de desarrollo. Principios de embriología experimental. La base genética del desarrollo. Comunicación en el desarrollo. Desarrollo embrionario temprano. Fecundación: el comienzo de un nuevo paradigma. Desarrollo temprano en invertebrados seleccionados. La genética de especificacioón del eje en drosophila. Desarrollo temprano y formación del eje en anfibios. Desarrollo temprano en los vertebrados: peces, aves y mamíferos. Desarrollo embrionario tardío. El surgimiento del extodermo: el sistema nervioso central y la epidermis. Células de la cresta neural y especificidad axonal. Mesodermo paraxial e intermedio. Lámina del mesodermo lateral y endodermo. Desarrollo de la extremidad de los tetrápodos. Determinación del sexo. Metamorfosis, regeneración y envejecimiento. La safa de la línea germinal. Ramificaciones adicionales de la biología del desarrollo. Una perspectiva general sobre el desarrollo de las plantas. Implicaciones médicas de la biología del desarrollo. regulación ambiental del desarrollo animal. Mecanismos de desarrollo del cambio evolutivo

PROLIFERATING INFLORESCENCE MERISTEM, a MADS-box gene that regulates floral meristem identity in pea.

SQUAMOSA and APETALA1 are floral meristem identity genes from snapdragon (Antirrhinum majus) and Arabidopsis, respectively. Here, we characterize the floral meristem identity mutation proliferating inflorescence meristem (pim) from pea (Pisum sativum) and show that it corresponds to a defect in the PEAM4 gene, a homolog of SQUAMOSA and APETALA1. The PEAM4 coding region was deleted in the pim-1 allele, and this deletion cosegregated with the pim-1 mutant phenotype. The pim-2 allele carried a nucleotide substitution at a predicted 5' splice site that resulted in mis-splicing of pim-2 mRNA. PCR products corresponding to unspliced and exon-skipped mRNA species were observed. The pim-1 and pim-2 mutations delayed floral meristem specification and altered floral morphology significantly but had no observable effect on vegetative development. These floral-specific mutant phenotypes and the restriction of PIM gene expression to flowers contrast with other known floral meristem genes in pea that additionally affect vegetative development. The identification of PIM provides an opportunity to compare pathways to flowering in species with different inflorescence architectures.