Reactive oxygen species (ROS) such as superoxide (O2–) and hydrogen peroxide (H2O2) are partially reduced oxygen molecules produced during cellular metabolism in all organisms. Plant chloroplasts and mitochondria are major ROS sources because of photosynthesis and aerobic respiration in these organelles. We previously found that the levels of oxidants were higher and antioxidants lower in maize (Zea mays) seedlings grown in the light than in the dark; these changes were accompanied by greater oxidative damage to the DNA in both chloroplasts and mitochondria in light-grown than dark-grown plants. In my research project, we will measure both H2O2 and antioxidants (catalase and peroxidase) after exposing dark-grown plants to light for increasing periods of time. Maize seedlings were grown in continuous darkness followed by 2, 4, 6, 12, and 24 hours of light. We then measured the levels of H2O2 and antioxidants in the chloroplasts and mitochondria isolated from leaf and stalk tissues during seedling development. Our data show the time course of ROS accumulation after the transfer from dark to light growth conditions and should provide a better understanding of the role of light in plant oxidative stress. Specifically, oxidative stress by ROS can be linked to DNA (mitochondria, plastid and organismal genomes) damage and by looking at the gradient of light exposure, it can open doors to discover how plants physiologically limit genetic impairment. This research can be used to assess more cancer-related topics in regards to ROS levels and how scientists can possibly find a solution in plant evolutionary-engineered genetics.

While pregnancies with multiple offspring are known among cetaceans, sources of differences in rates of monozygotic (identical) twins versus dizygotic (fraternal) twins across cetacean species are not highly studied. The present study determined the most likely proportions of monozygotic and dizygotic twins using Weinberg’s Differential Rule and a large historical data set supplied by years of whaling data across six cetacean species: blue whale (Balaenoptera musculus), fin whale (Balaenoptera physalus), sperm whale (Physeter macrocephalus) humpback whale (Megaptera novaeangliae), sei whale (Balaenoptera borealis), and Antarctic minke whale (Balaenoptera bonaerensis). Additionally, we use this data to test the hypothesis that twins are less likely to survive to birth compared to a single offspring, by testing whether the proportions of twins decrease with increasing fetus length in each species. All six cetaceans were more likely to have dizygotic twins than monozygotic twins, with the exception of the humpback whale. Probability of monozygotic twins were found to be 0%-29% in blue whale, 23%-44% in fin whale, 8%-54% in sperm whale, 14%-85% in humpback whale, 2%-25% in sei whale, and 9%-34% in Antarctic minke whale. This study has the potential to determine what factors govern successful twin pregnancies within cetaceans and provide a better understanding of the reproductive capabilities of the order.

Plant hormones are necessary for their growth, development, and overall function. Gibberellins (GAs) are a class of plant hormones that are used for cell elongation and growth. The GA pathway has been genetically manipulated in many crops to enhance agricultural yields. Research has also found that under elevated CO2 concentration conditions, GA dwarf plants revert to their less productive wild-type forms. This is very problematic for the agriculture industry because this reversion can potentially reduce their yields by half. Through my research, I hope to test whether modulation of GA signaling pathways can create crops that are more productive and better adapted to climate change. Interventions like this are needed because climate change is occurring more rapidly than plants are able to adapt to. Rewiring of the GA pathway is a potentially significant solution to this problem because we can modify plants in a manner that is likely transferable across many species. By using a novel genetic tool called a GA-sensitive Hormone Activated Cas9-based Repressor (GA HACR), we can modulate targeted genes in the GA hormone response pathway to turn down their transcriptional activity. The GA HACR targets specific genes through guide RNAs to repress the gene with complementary DNA sequence. The GA HACR is degraded in the presence of GA, which allows them to have a natural response to the activating hormone signal. We hypothesize that by targeting the HACRs to genes involved in GA biosynthesis (GA20 oxidase) and GA response (GID1 genes), we can modulate root growth of these plants. We are currently growing plants with ideal dwarf GA phenotypes in a CO2-enriched growth chamber to simulate future climate conditions and test how their growth responds. In this way, I will determine whether genetic intervention targeting the GA is a feasible strategy.

Herbivore associated molecular patterns (HAMPs) can be recognized by a plant’s immune system. Inceptin is a HAMP peptide that is present in the oral secretions of caterpillars and can be detected by plants in the legume subtribe Phaseolinae. Steinbrenner et al. recently identified the inceptin receptor (INR) which is native to legume species and is able to recognize and respond to the presence of inceptin. In order to validate that INR contributes to anti-herbivore defense responses, I am developing a variety containing the genetic background of a responsive accession, with an INR locus from an unresponsive accession. In order to create a near-isogenic line with a naturally occurring deletion, I am going through a process of crossing, backcrossing and screening. In order to create the new accession, I crossed a bean accession that has been shown to respond to inceptin with a bean accession that is not responsive to inceptin. The F1 progeny of this cross can then be screened using single nucleotide polymorphism genotyping to ensure that the plant is heterozygous for INR. The heterozygous F1 plants are backcrossed to the responsive parent plant, each time selecting for the resulting heterozygous plants. The backcrossing process is repeated a minimum of five times until I have an accession whose genome is almost completely that of the responsive parent, except the INR locus which is that of the non-responsive parent. I am creating a backcrossed accession between G19833 (genome sequenced Andean common bean) and a compatible, unresponsive accession Pv255 (Argentinian Phaseolus vulgaris). From this work, I hope to develop an accession that is able to test the contribution of INR to plant defense systems.

 Phytoliths are microscopic silica structures produced in plant tissue, and palms (family Arecaceae) are prolific producers of them. The stability of these structures contributes to the abundance of palms within the fossil record, as these structures can fossilize in sediments where leaves cannot, providing a wider range of evidence of the past palm geographic distribution. Palms generally grow in warmer and wetter environments, but certain species can live in more extreme climates (i.e., cold, dry). However, because 90% of palms are currently distributed around the equator and tropical rainforests, they are often used as an indicator of warmer environments in the fossil record. The current understanding of the taxonomic groups below the family level is limited, and it is unclear whether palm phytolith shape can be used to identify different palm groups in the fossil record. The Palm Project hopes to address this gap by testing phytolith classification using a morphometric approach. Over 100 species of known modern Arecaceae (~30 images/species) phytoliths have been imaged with a confocal microscope, and a semi-automated script in ImageJ quantifies the overall shape (globular or hat), density, and size of the phytolith ornamentations. Next, multivariate analysis on the morphometric data attempts to distinguish the phytoliths of various modern subfamilies based on distinct morphological traits, forming a quantitative baseline to describe and classify phytoliths. When combined with the collected ecological data, this could potentially identify signals between the environment of modern palm species and the phytoliths they form. Once the morphological differences between groups of modern palms are quantified, the same analysis can be applied to fossil phytoliths of unknown origins. This could reveal which taxonomic and ecological groups they belong to based on the most similar modern phytolith, giving insight into the phylogeny of Arecaceae and the paleoenvironment the fossils came from.