<p> During leaf senescence nutrients are mobilized towards newly developing vegetative and reproductive structures. The IAOx pathway that produces auxin and defense molecules [indole glucosinolates (IGs) and camalexin] is up-regulated during senescence. To investigate the role of the IAOx metabolites we isolated two independent cyp79B2/cyp79B3 double mutants, which are deficient in IGs and camalexin and had reduced auxin levels. Chlorophyll, protein, and gene expression data indicate that cyp79B2/cyp79B3 mutants display early leaf senescence. Furthermore, leaves accumulated higher levels of hydrogen peroxide and seed production was significantly reduced. Auxin signaling at hydathodes and vascular tissue decreased as leaves aged, even though endogenous auxin levels increased. Since CYP79B2/CYP79B3 play only a minor role in auxin synthesis, it is most likely that IGs and/or camalexin are playing a protective role during age-induced developmental leaf senescence. Identifying molecules that slow down the rate of senescence may allow for genetic manipulation to increase nutritional value and crop yield</p>

The cotton (Gossypium hirsutum L.) necrotic leaf-spot mutation is due to a single recessive gene. Cytologically the necrotic leaf-spot mutant affects the development and necrosis of leaves associated with the changed staining pattern, contraction and collapse of palisade and spongy parenchyma cells sequentially. The scanning electron microscope revealed that the stomata are also involved or affected by necrosis. The mutation exhibits a slightly deleterious effect on pollen viability, but not on the viability of the embryo.

Yield and quality of nondormant alfalfa (Medicago sativa L.) may be reduced by winter frost. This study surveyed 12 populations for injury and regrowth following artificial frost. Approximately 40 plants per population were grown in a greenhouse for 70 d in styrofoam flats for each of 2 treatments (control and frost) with 4 replications. At 70 d of age, plants were clipped to 4 cm, regrown for 14 d, exposed to 5°C for 5 d to harden, and then exposed to -3°C for 6-8 h. After 2-3 d plants were scored for damage, stem height and stem number. Measurements were repeated weekly for 21 d, including a final damage score. Simulated selection comparing index selection and direct selection demonstrated positive response to selection in all populations analyzed. Selection for growth rate ratio resulted in reduced damage score, while selection for reduced damage did not improve growth rate ratio. Index selection improved both traits. Results indicate that response following frost in alfalfa may be improved.

The objectives of this study were to describe demographic change in an alfalfa population and determine whether genetic changes were associated with stand loss in an alfalfa field during the year of establishment. A nondormant composite population (AZ-88NDC) was sown at 1944 seeds per square meter in Oct. 1988 at Tucson, AZ. Only 29% of the seeds sown germinated and emerged. Survivorship curve of the emerged seedling population had some characteristics of Deevey type III. Two heavy mortality periods were observed. Low temperatures might be the major cause of the first heavy stand loss. The second significant stand loss could be explained by increased density stress. Isozyme profiles were produced from 60 day survivors dug from the field, unselected greenhouse-grown AZ-88NDC (='Unsel') and 300-d progenies produced by intermating plants surviving 300 days. Significant differences were observed in overall level of population heterozygosity of 60-d and unselected populations based on fixation indices of six isozyme loci. This suggests that genetic changes may be associated with establishment of an alfalfa stand.

Three maize populations developed for their ability to withstand drought and salinity, and their reciprocal F1 crosses were tested under induced water stress and normal moisture conditions. Two commercial hybrids and one open-pollinated variety were also included in the study. The objective was to investigate yield and its components under induced drought. Significant differences in yield were observed in both irrigation treatments. DeKalb 689, one of the commercial hybrids, outyielded all the other entries under wet conditions, whereas under dry conditions the open-pollinated variety, Page Ranch, had the highest yield. Significant differences between populations and their hybrids were also observed. Significant correlations were noted in grain yield as observed in wet and dry conditions and the reduction in the number of ears per plant was positively correlated with the reduction in grain yield resulting from drought.

Understanding patterns of genetic diversity in crop species may enhance the efficiency of germplasm conservation and utilization. Nondormant alfalfa (Medicago sativa L.) is an important forage crop in southwest Arizona, and originates from low elevations of the Middle East and India. This study examined 60 accessions of nondormant alfalfa from India, north Africa and Arabia in a field trial in Tucson, AZ during 1989-91. Nondormant Indian and African alfalfas have previously been considered independent germplasm sources. Principal components of 6 morphological and 15 agronomic traits were used to classify accessions using average linkage cluster analysis. Low elevation Indian accessions did not differ phenotypically from most African and Arabian alfalfas. This indicates that Indian alfalfas are not an independent source of germplasm in need of conservation as such, but western Arabian alfalfas may be.

<p> The yeast <i>Yarrowia lipolytica</i> naturally produces ammonia and oils from protein substrates. The protein residue in the waste material from fermentations in a biorefinery can be utilized by this strain in order to produce additional bioproducts. In order to improve the amount of ammonia and oil produced, <i>Y. lipolytica</i> NRRL YB-567 was irradiated with UV-C and the resulting mutant strains were screened for ammonia production on plates containing bromothymol blue. Seven mutant strains were selected based on increased ammonia production (indicated by deep blue color) and colony density. The mutant strains were evaluated for ammonia production, protein utilization, growth rate, oil production, and 2-phenylethanol production. Oil composition was also evaluated for the mutant strain that produced the most oil relative to all other strains. Of the seven mutant strains, 5 produced more ammonia than the wild-type strain while only one strain produced more oil than the wild-type strain. The mutant strain has potential applications for use in biorefineries to produce valuable commercial products.</p>

<p>Soybean (Glycine max) yield is significantly affected by soybean cyst nematode (SCN), Heterodera glycines, and causes an annual loss of billions of US dollars. In this study, Glycine max xyloglucan endotransglycosylase/hydrolase gene (Gm-XTH52) was transformed into a nematode susceptible G. max [Williams 82/PI 518671] variety of soybean to test whether the protein expression has a role in resistance to H. glycines, and possible chemical changes the expression may cause in the plant composition. Expression level of the Gm-XTH52 gene was three times higher than in controls. Significant reduction in the number of SCN cysts suggested suppression of H. glycines parasitism upon transformation. While total sugar amounts did not significantly differ between the transformed and control plants, xyloglucan amounts of loosely bound sugars of genetically mosaic plants were significantly lower in comparison to controls. Control plants showed lower molecular weight sugars than the transformed plants not subjected to H. glycines infection.

<p> Genome sequencing technology has enabled the identification of genetic variants that are linked with cancer phenotypes, whether these are somatically acquired mutations or common inherited single nucleotide polymorphisms (SNPs). Whereas coding variants have been reported to disrupt protein function to promote cancer, most variants map to noncoding regions, with no known function. Recently, much effort has gone into annotating the human noncoding genome, enabling the characterization of the functional basis of noncoding SNPs. As an example of functional impact, breast cancer (BrCa) risk-associated SNPs can alter transcription factor binding at distal enhancers. </p><p> Identifying the targets of risk SNPs remains a challenge. One reason for this is the complex three-dimensional structure of the genome. Local chromatin openness correlates with chromatin activity, and sites of chromatin that are open concurrently across multiple cell types indicates a functional relationship between them. We mapped BrCa risk-associated SNPs to regions of open chromatin to predict the most likely functional risk SNPs. Then, we predicted their targets by identifying the gene promoters whose openness correlated with these risk regions. Further, we validated a gene which is a novel therapeutic target and relevant in breast cancer biology. </p><p> In addition to SNPs, noncoding somatic mutations are also predicted to play a role in cancer. In 2012, driver mutations were reported in the telomerase gene promoter, hinting at the relevance of mutations in regulatory elements. This is particularly true when considering oncogenes whose elevated expression in certain cancers is not attributable to coding mutations or copy number amplification. We reveal the enrichment and functional nature of somatic mutations mapping to enhancers that regulate the estrogen receptor gene, which is known to drive over two-thirds of breast cancer. </p><p> Attributing function to noncoding SNPs and mutations associated with cancer risk and progression is a growing necessity in this era of whole-genome cancer biology. This thesis demonstrates a methodology to identify the functional consequence and gene targets of significantly mutated or risk variant-bearing enhancer sets to narrow the gap between known and unknown risk factors in BrCa.</p>

It is often proposed that the shape of animals evolves as a correlated response to selection on life history traits such as whole body growth and differentiation rates. This scenario is certainly true for shape variation that is an allometric consequence of body size variation, because body size is determined by growth and differentiation rates. However, we are aware of few examples in which development rate variation is correlated with body size-independent shape variation. In this study on the green treefrog, Hyla cinerea, we test whether that fraction of the variance in tibiofibula length and head width that is left after removing snout vent length as a covariate is correlated with either genetically or environmentally based variation in development rates. / Size-adjusted tibiofibula length and head width at metamorphosis are both positively genetically correlated with larval period length. Thus, relative limb and head proportions in adult treefrogs could evolve as a correlated response to selection on a larval life history trait. Neither larval growth rate nor juvenile growth rate is significantly genetically correlated with the morphological traits. The two size-adjusted morphological traits are strongly genetically correlated with each other, a situation which could either hinder or accelerate their joint evolution, depending on the directions of selection. / The growth rate of larvae raised under different food levels and temperatures had no effect on their size-adjusted head width or tibiofibula length at metamorphosis. The food-controlled rate at which small juveniles became large ones also had no influence on their shape. However, the head width versus snout vent length relationship among metamorphs has a shallower slope than the same relationship within growing juveniles. Thus, size at metamorphosis alone controls head width at a given larger body size. To our knowledge, we are the first to identify this difference in allometries as a potential source of size-independent shape variation in adult frogs. / Source: Dissertation Abstracts International, Volume: 51-01, Section: B, page: 0106. / Major Professor: Joseph Travis. / Thesis (Ph.D.)--The Florida State University, 1989.