Encouraging Science Communication through Deliberative Pedagogy: A Study of a Gene Editing Deliberation in a Nonmajors Biology Course.

Deliberative pedagogy encourages productive science communication and learning through engagement and discussion of socio-scientific issues (SSI). This article examines a two-day deliberation module on gene editing that took place in an introductory nonmajors biology course, furthering research on integrating deliberative discussion into the biology classroom. The results demonstrate the benefits of a single, episodic deliberation in the classroom, which can positively encourage active discussion and critical awareness of connections between biology and real-world issues, thus contributing to the development of scientific citizenship. Additionally, the findings show that gene editing is an apt SSI topic for the deliberative process because it encourages productive communication practices of scientific citizenship, including discussion, perspective taking, questioning, and consideration of different types of evidence when coming to a decision.

Evolutionary history of chloridoid grasses estimated from 122 nuclear loci.

Chloridoideae (chloridoid grasses) are a subfamily of ca. 1700 species with high diversity in arid habitats. Until now, their evolutionary relationships have primarily been studied with DNA sequences from the chloroplast, a maternally inherited organelle. Next-generation sequencing is able to efficiently recover large numbers of nuclear loci that can then be used to estimate the species phylogeny based upon bi-parentally inherited data. We sought to test our chloroplast-based hypotheses of relationships among chloridoid species with 122 nuclear loci generated through targeted-enrichment next-generation sequencing, sometimes referred to as hyb-seq. We targeted putative single-copy housekeeping genes, as well as genes that have been implicated in traits characteristic of, or particularly labile in, chloridoids: e.g., drought and salt tolerance. We recovered ca. 70% of the targeted loci (122 of 177 loci) in all 47 species sequenced using hyb-seq. We then analyzed the nuclear loci with Bayesian and coalescent methods and the resulting phylogeny resolves relationships between the four chloridoid tribes. Several novel findings with this data were: the sister lineage to Chloridoideae is unresolved; Centropodia+Ellisochloa are excluded from Chloridoideae in phylogenetic estimates using a coalescent model; Sporobolus subtilis is more closely related to Eragrostis than to other species of Sporobolus; and Tragus is more closely related to Chloris and relatives than to a lineage of mainly New World species. Relationships in Cynodonteae in the nuclear phylogeny are quite different from chloroplast estimates, but were not robust to changes in the method of phylogenetic analysis. We tested the data signal with several partition schemes, a concatenation analysis, and tests of alternative hypotheses to assess our confidence in this new, nuclear estimate of evolutionary relationships. Our work provides markers and a framework for additional phylogenetic studies that sample more densely within chloridoid tribes. These results represent progress towards a robust classification of this important subfamily of grasses, as well as proof-of-concept for hyb-seq next-generation sequencing as a method to generate sequences for phylogenetic analyses in grasses and other plant families.

Molecular phylogenies disprove a hypothesized C4 reversion in Eragrostis walteri (Poaceae).

BACKGROUND AND AIMS: The main assemblage of the grass subfamily Chloridoideae is the largest known clade of C(4) plant species, with the notable exception of Eragrostis walteri Pilg., whose leaf anatomy has been described as typical of C(3) plants. Eragrostis walteri is therefore classically hypothesized to represent an exceptional example of evolutionary reversion from C(4) to C(3) photosynthesis. Here this hypothesis is tested by verifying the photosynthetic type of E. walteri and its classification. METHODS: Carbon isotope analyses were used to determine the photosynthetic pathway of several E. walteri accessions, and phylogenetic analyses of plastid rbcL and ndhF and nuclear internal transcribed spacer DNA sequences were used to establish the phylogenetic position of the species. RESULTS: Carbon isotope analyses confirmed that E. walteri is a C(3) plant. However, phylogenetic analyses demonstrate that this species has been misclassified, showing that E. walteri is positioned outside Chloridoideae in Arundinoideae, a subfamily comprised entirely of C(3) species. CONCLUSIONS: The long-standing hypothesis of C(4) to C(3) reversion in E. walteri is rejected, and the classification of this species needs to be re-evaluated.

The origin and evolution of Eragrostis tef (Poaceae) and related polyploids: evidence from nuclear waxy and plastid rps16.

Tef (Eragrostis tef; Poaceae) is an allotetraploid (2n = 4x = 40) cereal crop whose origin within the large genus Eragrostis is unknown. Previous studies have suggested a total of 14 wild Eragrostis species as potential progenitors. Phylogenetic analysis of sequence data from the nuclear gene waxy and the plastid locus rps16 strongly supports the widely held hypothesis of a close relationship between tef and E. pilosa, a wild allotetraploid. Eragrostis heteromera, another previously proposed progenitor, is shown by the waxy data to be a close relative of one of the tef genomes. Other putative progenitors included in the taxon sample are not supported as closely related to tef. Plastid sequences from five varieties of tef and four E. pilosa accessions are identical and therefore are uninformative with respect to the question of multiple origins of these polyploids. The waxy phylogeny also resolves the relationships among other allopolyploids, supporting a close relationship between the morphologically similar allotetraploids E. macilenta, E. minor, and E. mexicana. Eragrostis cilianensis, another morphologically similar allopolyploid, appears to have shared one diploid progenitor with these species but derived its other genome from an unrelated diploid.