Nitrogen fixation in plants was long considered to be accomplished only by bacteria living in the root nodules of leguminous plants such as beans, alfalfa and peas. However, it is becoming increasingly apparent that many microbes live all throughout the insides of the shoot and root tissues, which serve important roles as symbionts in a broader range of plant hosts. Many of these so called "endophytitic" microbes are capable of nitrogen fixation, and our lab's and others' research has shown that certain endophytes can increase plant growth, confer drought tolerance, and reduce the need for chemical fertilizers. In order to better understand these endophytes, I am working on one of our lab’s most promising bacteria, WP5, to generate a mutant which lacks a functional copy of a gene necessary for nitrogen fixation, nifH, but is otherwise genetically identical to its predecessor. This will serve as an ideal negative control for future experiments involving WP5. Additionally, I am working to analyze the regulation of nifH RNA expression in the presence of various environmental and nutritional conditions.

Every plant needs Nitrogen to grow. Nitrogen is usually given through synthetic fertilizer which is expensive and causes a lot of environmental problems. Synthetic fertilizer is bad for the envieronment not only it need a lot of fossil fuel to make the high temperature and pressure condition for Nitrogen reaction, but also excess Fertilizer will bring blooming algae to the surround ponds, which will make the organism in the water die out because lack of Oxygen since the sunshine cannot get through algae and help underwater plants to photosynthesis. Since previous research in the lab showed that endophytes isolated from Willow and Poplar trees can promote growth of crops such as pepper, tomatoes, and sweet corn under low nitrogen conditions, we hope that Endophyte can reduce or completely substitute synthetic fertilizer of other commercial plants, such as corn. Endophytes (microbes living inside plants) can produce phytohormones and provide fixed nitrogen for plants. My research focuses on corn, a bioenergy crop species typically grown with large inputs of fertilizer. I screened ten commercial varieties of corn and compared the growth of endophyte inoculated plants with the uninoculated controls, in low nitrogen soil. In one variety of corn there was increased biomass in the inoculated plants compared to the controls. Currently I am testing which isolate is responsible for the plant growth promotion. These findings will have a great impact on commercial production of corn in a sustainable way.

 The first floral mutations ever documented, double flowers have been prized for centuries for their beauty. The double mutant variants ‘Shoaf’s Double’ and ‘Cameo’ are found in Thalictrum thalictroides, a member of the buttercup family. The purpose of this research is to determine the genetic mutation underlying this desirable phenotype. We predicted that a mutation in a C-class floral organ identity gene would cause the homeotic transformation (conversion of one organ type to another) of stamens and carpels to petalloid sepals in this species. C-class genes are also involved in floral determinacy, the termination of floral organ growth, which is why double flowers appear to have a second flower nested inside the first. As expected, the expression of the C-class gene ThtAG1 was greatly reduced in our mutants. Finding no changes in the coding region from wild type, we further investigated the entire genomic locus, where we found evidence of the action of a transposable element in both mutants. In ‘Shoaf’s Double’ a Mutator Like Element (MuLE) has inserted itself into a regulatory intron of TthAG1, disrupting its function. In ‘Cameo’ a ‘footprint’ at the exact same place in the sequence indicates that the same element may have jumped out, deleting a section of the intron. We hypothesize that the double phenotype in ‘Cameo’ is likely due to the accumulation of mutations before the MuLE jumped out. Since the MuLE’s transposase is expressed in ‘Shoaf’s Double’ (but not in wildtype), these results illustrate the rare case of an autonomous transposable element underlying a regulatory mutation that results in a visible phenotype. We hope that our work will provide insight into the genetic basis for the double phenotype of popular commercial flowers such as roses, camellias and carnations.

In the model organism Arabidopsis thaliana, the B-class genes of flower development are responsible for proper formation of petals and stamens in a flower. Studies in Thalictrum thalictroides, a representative of the sister lineage to all other eudicots provides insight into the ancestral function of the B-class genes. Unlike Arabidopsis, the flowers of T. thalictroides lack petals, and yet the sepals are large and colored similar to petals. Here, we investigate the function of B-class proteins in T. thalictroides through the study of the horticultural mutant known as ‘Betty Blake.’ The ‘Betty Blake’ mutant phenotype consists of many non-petaloid (green) sepals and carpels but no stamens. We have previously shown reduced expression of most B class genes in ‘Betty Blake’, yet we were not able to find any meaningful mutations in these loci. Therefore, we hypothesize that an upstream regulator of the B-class genes may be mutated in ‘Betty Blake’. UNUSUAL FLORAL ORGAN (UFO) is a known upstream regulator of the B-class genes and is therefore a logical candidate. We hypothesize that the UFO mutation is the cause of the B class phenotype in ‘Betty Blake.’ The investigation of B-class function in this non-core eudicot has provided us with insight into the evolution of gene regulatory networks affecting ectopic petaloidy and stamen identity that we will continue to pursue in future experiments.

Stickseed (Hackelia) is a genus of plants comprised of about forty species distributed primarily across the dry forests and mountains of interior western North America. This study seeks to build an evolutionary tree of Hackelia using DNA sequences from both the chloroplast and nuclear genomes. Preliminary analyses suggest possible conclusions regarding their geographic history and the evolution of their fruit characteristics. While it is currently unclear where the genus started, it appears there were two major migrations; one started in Washington and moved southward into Mexico, while another started in the Midwest and traveled southwest into California, Mexico, and Peru. Consequently, California is a diversity hotspot for this genus. Hackelia, like the rest of its family, has a fruit that divides into four nutlets at maturity. However, Hackelia is unique from other genera; it possesses elaborate prickles on its nutlets. These prickles can be described using two physical traits: whether the prickles along the border of the nutlet (marginal prickles) fuse to form a cup-like border, and if there additional prickles between the marginal prickles (intramarginal prickles). Our results suggest that ancestral species had nutlets with a cup-like border of marginal prickles and obvious intramarginal prickles. Most species of the genus have since lost the cup-like border, resulting in free marginal prickles. On the other hand, while most species have retained their intramarginal prickles, at least three lineages spread across the tree have lost them. This study will help us understand how plants have diversified in western North America, as well as how physical traits can be evolutionarily variable or conservative. 

The plant genus Thalictrum (meadow-rues) contains numerous shifts in ploidy number, ranging from diploid (2x) in the earliest diverging species to 24x in recently derived species. Polyploidy can result from a whole genome duplication event within an individual (autopolyploidy) or following a hybridization event (allopolyploidy). The rates and evolutionary consequences of these two mechanisms of polyploidy are currently under debate, and I am therefore attempting to estimate their relative roles within this genus using a phylogenetic approach. The current Thalictrum phylogeny relies on chloroplast DNA and nuclear ribosomal regions, which tend to underestimate the role of hybridization due to maternal inheritance and concerted evolution patterns, respectively. I am using single-copy nuclear genes to uncover potential hybridization signals in Thalictrum’s evolutionary history. This information will be used to compare the relative numbers of autopolyploids and allopolyploids in the genus. I hypothesize that allopolyploidy played a larger role in shaping the diversity of this genus, due to its potential for differential survival and reproduction as a consequence of immediate, novel gene expression in hybrid progeny. Furthermore, this analysis will estimate the hybrid origins of particular alleles within a species. In the future, this information will be applied to questions on the evolution of genes involved in flower development after whole genome duplications.

Pollination syndrome refers to suites of floral traits that influence biotic or abiotic vectors transporting pollen from one flower to another. These traits typically include flower color, position, shape, size, scent and reward. Scent is a major component of pollination syndrome, as the volatile organic compounds (VOCs) that compose “scent” often attract pollinators or deter predators. The genus Thalictrum in the Ranunculaceae (buttercup family) includes both insect- and wind-pollinated species, enabling comparisons of the role of scent in floral diversification among recently diverged taxa with distinct pollination syndromes. To characterize floral scent, we identified and compared the bouquet of VOCs emitted by insect- and wind-pollination species, as well as by floral vs. vegetative tissue. Scent was collected from tissue samples by traps in a filtered air system, then eluted and analyzed with gas chromatography mass spectrometry. Quantitation and emission rate were calculated to generate floral bouquets. Electroantennograms were performed on selected compounds to examine pollinator response. Focusing on eleven species representative of the two pollination syndromes and spanning the Thalictrum phylogeny, we identified ten key compounds of which five are deterrents against herbivory, two are pollinator attractants, and three have unknown functions. Given that these scent profiles consist primarily of defensive rather than attractive compounds, we hypothesize that repeated transitions from insect- to wind-pollination in Thalictrum may be due to the breakdown of an ancestrally weak insect pollination syndrome. Moreover, scent bouquets appear to follow phylogenetic patterns more so than pollination mode. The variation in distribution of VOCs across species in a phylogenetic framework allows us to test evolutionary patterns of compound co-option during evolution.

Pollination is often facilitated by insects and animals guided to flowers by a mixture of volatile compounds: the components of floral scent. As an attractive cue for pollinators, scent emission may be highly regulated so that its release coincides with the activity of its preferred pollinator. This relationship is particuarly evident in the release of benzenoid volatiles by Petunia, through which it attracts its pollinator, the nocturnal hawk moth (Sphingidae). Though Petunia release volatile benzenoid compounds nocturnally through a process mediated by the circadian clock, the molecular mechanisms responsible remain uncharacterised. We hypothesise that the transcription of the ODORANT1 (ODO1) gene in Petunia, which encodes a key transcription factor involved in regulation of volatile benzenoid synthesis, is regulated by an ortholog of the highly conserved Arabidopsis core-clock genes - CIRCADIAN CLOCK ASSOCIATED 1 (CCA1)/LATE ELONGATED HYPOCOTYL (LHY) - in Petunia. To investigate this potential association, we have characterised the Petunia ortholog of LHY (PhLHY) and will look to analyse its influence on volatile benzenoid production. We aim to understand the interaction between the PhLHY protein and ODO1, and will investigate the intracellular localisation of PhLHY as well as the tissue specific expression of ODO1. We anticipate that PhLHY will influence the rhythmic oscillation of the circadian clock, as well as influence the synthesis and emission of floral volatiles by directly regulating ODO1. In elucidating the mechanisms by which the circadian clock control scent emission, we will likely be able to generate floral varieties that display significant chronological shifts in their daily scent emmision regimes.