Functional analysis of various conserved domains of NPH3 involved in phototropism in Arabidopsis thaliana

Abstract only availablePhototropism - the directional growth (curvature) for a plant towards light, is a very important adaptive response in plants in order for them to maximize photosynthesis. Blue light triggers phototropic response in Arabidopsis thaliana via the dominant photoreceptor phototropin 1 (phot1). Genetic studies have identified several genes that encode phot1 interacting proteins. Of these, currently, only NON PHOTOTROPIC HYPOCOTYL 3 (NPH3) is known to be absolutely required for phototropism. nph3 mutants are completely aphototropic, resembling phot1 null mutants. NPH3 is a phosphoprotein containing a BTB and a coiled coil domain, and the dephosphorylation of this protein into its active state in light is known to be entirely phot1 dependant. Yet little is known of the role of NPH3 as a mediator in the phototropic signal-response pathway. To better understand the role of conserved domains of NPH3 in phototropism, a range of serial deletions and mutants of NPH3 were generated, driven by its own native NPH3 promoter and the constitutive CaMV 35S promoter in nph3-6 and wild-type Col-0 backgrounds respectively. All truncated and mutant NPH3 proteins were also translationally fused with a green fluorescent protein (GFP). Multiple T3 homozygous transgenic lines were evaluated by comparing average angles of hypocotyl curvature with those of aphotoropic nph3-6 and wild-type Col-0. Over-expression of NPH3 or different portions of NPH3 in Col-0 resulted in reduced phototropism. Selective expression of the NPH3 domains under the native promoter could not complement the null nph3-6 phenotype. The alterations in the subcellular localization of these transgenic lines were also investigated using confocal fluorescence microscopy.NSF Plant Genomics Internship @ M

Physiological responses of a hyper-phototropic mutant to various light stimuli [abstract]

Abstract only availableFaculty Mentor: Mannie Liscum, Biological SciencesPhysiological responses of a hyper-phototropic mutant to various light stimuli Phototropic responses are the directional curvature of organs in response to differences in light intensity and/or quality. The experimental plant is the hyper-phototropic hypocotyl () mutant that is associated specifically with phototropism and is hyper-responsive to blue light stimulation. In wild-type seedlings the response is dependent upon the fluence of blue light (number of incident of photons) used to stimulate seedlings. In this analysis seedlings were exposed to several fluence rates of blue light. Results from these experiments suggest that the phenotypes are specific to lower fluence rates. Additionally, red light which has been shown to enhance the phototropic response to blue light was used as a pretreatment to assess whether is altered in its response to red light as well as blue. Results from this latter analysis show that mutant seedling still exhibit a higher degree of curvature than control samples, suggesting the red light enhances the phototropic response of as well. Together these experiments suggest that affects a repressor of phototropin 1-dependent phototropism in low blue light conditions.University of Missouri--Columbia. Office of Undergraduate ResearchPlant Genomics Internship @ M

Expression of aT4g27260/GH3-5/GH3a studied with in situ hybridization

Abstract only availableTropisms, the responses of plants to external stimuli, have been studied as important evolutionary adaptations and as possible areas of future advantageous genetic manipulation. The goal of our current research is to identify targets of NPH4/ARF7 activity in the elongating hypocotyl cells of tropically-stimulated seedlings. The finding that NPH4/ARF7 is necessary for establishment of phototropic and gravitropic curvature lends credence to the long-held notion that a tropic curve requires formation and response to localized changes in auxin concentration. As a result of previous microarray experiments, we have isolated a suite of eight targets that are potentially under the control of NPH4/ARF7, and therefore acting in response to an auxin gradient. One of the targets is a member of the GH3 family, At4g27260/GH3-5/GH3a. Many of the GH3 family members have been shown to be responsive to, or to be regulated by, auxin. In order to elucidate the expression of At4g27260/GH3-5/GH3a in tropically-stimulated Brassica seedlings, in situ hybridization with sense and antisense RNA probes is being performed. These experiments are meant to clarify where At4g27260/GH3-5/GH3a is expressed in the stem in response to tropic stimulation. These experiments will provide critical insight into how At4g27260/GH3-5/GH3a is regulated under physiological conditions and suggest future experiments to test the functional significance of the encoded protein in the establishment of tropic curves.Plant Genomics Internship @ M

Natural variation in phenotypes associated with phototropins among geographically isolated populations of Arabidopsis thaliana [abstract]

Abstract only availableIn Arabidopsis thaliana several phenotypes are controlled by blue light including chloroplast relocation movements and bending of the seedling stem in phototropism. These responses are controlled by the phototropins, phot1 and phot2. Chloroplasts move towards the brightest area in a plant cell under low light intensity to maximize light interception (accumulation response), but toward darker areas under high intensity light to minimize photo-damage (avoidance response). Phot1 and phot2 control the accumulation movement, but phot2 alone controls the avoidance response. Phototropism in response to weak blue light is controlled solely by phot1. Here, we have tested seventeen different accessions of A. thaliana for phenotypes uniquely associated with phot1 and phot2 and examined variation in phot1 and phot2 sequence data for a small subset. Accessions were chosen to better understand the ecological context of variation in phototropin function in nature.National Science Foundation grant to M. Liscu

Plant Adaptation to Drought --- Interdisciplinary Research at the University of Missouri [abstract]

Only abstract of poster available.Track V: BiomassDrought is the most important cause of crop failure in Missouri and limits plant productivity in large parts of the US and the world. Drought induces severe reductions in average annual crop yields on a regional scale and can have devastating effects at the farm level. Regional droughts can also strikingly reduce net primary productivity of natural ecosystems. Research on plant adaptation to drought is a long-standing, important component of MU faculty members, who comprise a strong, collaborative team of university and USDA-ARS scientists and are among the international leaders in drought research. Group members represent expertise from a broad range of disciplines, including plant physiology, agronomy, forestry, plant breeding, molecular biology, biotechnology, entomology, plant pathology, and soil science. Areas of research span from basic to applied aspects of plant adaptation to drought, fostering the translation of basic discoveries of underlying mechanisms to the delivery of more drought-tolerant crops at the doorsteps of American farmers. In addition to local collaborations, the team interacts with other scientists in the state of Missouri (e.g. Danforth Plant Sciences Center and Washington University in St. Louis) and at the national and international levels (including Australia, England, India, Mexico [CIMMYT], and The Philippines [International Rice Research Institute]). Active research projects conducted by the drought community at MU include research funded by state, federal, commodity group (e.g. Missouri Soybean Merchandising Council, United Soybean Board, Cotton Inc.) and private (Monsanto, Syngenta) sources. Of particular note, members of the group were recently awarded over $1.5 million from the Missouri Life Sciences Research Board to establish “rainout shelters” that will allow control of precipitation under field conditions. The ability to manage the timing, duration, and intensity of water deficit stress under field conditions is essential to examine plant responses to drought and interactions of drought and biotic stresses in mid-western environments. The track record of excellence in drought research and the broad range of expertise of the interdisciplinary group provide fertile grounds for creative and productive research endeavors that are directed to optimize crop and woody plant biomass production