Browsing by Author "Donahue, Janet L."

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    Certain Malvaceae Plants Have a Unique Accumulation of myo-Inositol 1,2,4,5,6-Pentakisphosphate
    Phillippy, Brian Q.; Perera, Imara Y.; Donahue, Janet L.; Gillaspy, Glenda E. (MDPI, 2015-05-29)
    Methods used to quantify inositol phosphates in seeds lack the sensitivity and specificity necessary to accurately detect the lower concentrations of these compounds contained in the leaves of many plants. In order to measure inositol hexakisphosphate (InsP6) and inositol pentakisphosphate (InsP5) levels in leaves of different plants, a method was developed to concentrate and pre-purify these compounds prior to analysis. Inositol phosphates were extracted from leaves with diluted HCl and concentrated on small anion exchange columns. Reversed-phase solid phase extraction cartridges were used to remove compounds that give peaks that sometimes interfere during HPLC. The method permitted the determination of InsP6 and InsP5 concentrations in leaves as low as 10 µM and 2 µM, respectively. Most plants analyzed contained a high ratio of InsP6 to InsP5. In contrast, certain members of the Malvaceae family, such as cotton (Gossypium) and some hibiscus (Hibiscus) species, had a preponderance of InsP5. Radiolabeling of cotton seedlings also showed increased amounts of InsP5 relative to InsP6. Why some Malvaceae species exhibit a reversal of the typical ratios of these inositol phosphates is an intriguing question for future research.
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    Regulation of Sucrose non-Fermenting Related Kinase 1 genes in Arabidopsis thaliana
    Williams, Sarah P.; Rangarajan, Padma; Donahue, Janet L.; Hess, Jenna S.; Gillaspy, Glenda E. (2014-07-10)
    The Sucrose non-Fermenting Related Kinase 1( SnRK1) proteins have been linked to regulation of energy and stress signaling in eukaryotes. In plants, there is a small SnRK1 gene family. While the SnRK1.1 gene has been well studied, the role other SnRK1 isoforms play in energy or stress signaling is less well understood. We used promoter:GUS analysis and found SnRK1.1is broadly expressed, while SnRK1.2 is spatially restricted. SnRK1.2 is expressed most abundantly in hydathodes, at the base of leaf primordia, and in vascular tissues within both shoots and roots. We examined the impact that sugars have on SnRK1 gene expression and found that trehalose induces SnRK1.2 expression. Given that the SnRK1.1 and SnRK1.2 proteins are very similar at the amino acid level, we sought to address whether SnRK1.2 is capable of re-programming growth and development as has been seen previously with SnRK1.1 over expression. While gain-of-function transgenic plants over expressing two different isoforms of SnRK1.1 flower late as seen previously in other SnRK1.1 over expressors, SnRK1.2 over expressors flower early. In addition, SnRK1.2 over expressors have increased leaf size and rosette diameter during. Early development, which is the opposite of SnRK1.1 over expressors. We also investigated whether SnRK1.2 was localized to similar subcellular compartments as SnRK1.1, and found that both accumulate in the nucleus and cytoplasm in transient expression assays. In addition, we found SnRK1.1 accumulates in small puncta that appear after a mechanical wounding stress. Together, these data suggest key differences in regulation of the SnRK1.1 and SnRK1.2 genes in plants, and highlights differences over expression of each gene has on the development of Arabidopsis.