75 Integrating Membrane Transport with Male Gametophyte ... - TAIR

77 Alterations in Sphingolipid Hydroxylation Have Profound Effects on Plant Growth and
Sphingolipid Composition
Ming Chen 1 , Jonathan Markham 1 , Charles Dietrich 2 , Jan Jaworski 1 , Edgar Cahoon 2
1
Donald Danforth Plant Science Center, 975 N. Warson Rd., St. Louis, MO 63132, 2 USDA-ARS Plant Genetics
Research Unit, Donald Danforth Plant Science Center
Sphingolipids are major structural components of the plasma membrane and tonoplast of plant cells and are enriched,
along with sterols, in detergent resistant membrane fractions or lipid rafts prepared from plasma membrane. Lipid rafts
are also enriched in GPI-anchored proteins, which have been linked with a number of cell surface-related functions,
including cell wall synthesis and signal transduction. One goal of our research is to understand the effects of sphingolipid
composition on plant growth and development. In this study, Arabidopsis mutants with defects in the C-4 hydroxylation
of sphingolipid long-chain bases (LCBs) were characterized. The C-4 LCB hydroxylase catalyzes the conversion of
dihydroxy LCBs to the trihydroxy form. Typically, ~90% of the sphingolipids in Arabidopsis leaves contain tri-hydroxy
LCBs. Two genes for the C-4 LCB hydroxylase occur in Arabidopsis. T-DNA mutants for either gene displayed partial
reductions in the tri-hydroxy LCB content of sphingolipids. These mutants, however, had no observable growth phenotype.
By contrast, double mutants of the two hydroxylase genes, which completely lacked trihydroxy LCBs, were severely
dwarfed and did not bolt. By use of RNAi, reductions in the growth of plants were found to be closely correlated with
the trihydroxy LCB content. In addition, global analysis of sphingolipids in the C-4 hydroxylase mutants revealed large
alterations in the composition of all sphingolipid classes. These results demonstrate that relatively small changes in
the structure of sphingolipids (e.g. the loss of a single hydroxyl group) can have profound effects on the growth and
development of Arabidopsis.
This work was supported by a National Science Foundation Arabidopsis 2010 grant (MCB-0313466) "Collaborative Research: The Synthesis
and Function of Arabidopsis thaliana Sphingolipids."
78 Authentic Investigations as Pedagogical Tool for Learning Scientific Inquiry
David Lally, Julia Grady, Dayna Wilhelm, Marshall Swafford, Erin Dolan
Virginia Tech
We hypothesize that, by engaging in authentic investigation (i.e., experiments that have no known outcomes and
that are of interest to the broader scientific community), students can learn the process of scientific inquiry, especially
determining how data constitute evidence, generating alternative explanations, and making connections between evidence
and explanations. We anticipate that authentic investigations can serve as a sustainable mechanism for partnership
among students, teachers, and scientists because they are bi-directional in nature and execution and they consider the
needs and resources of all partners. For example, students can offer many pairs of hands, teachers can offer expertise in
communicating with non-technical audiences, and scientists can offer experimental resources and know-how. An inquirybased
biotechnology education program, the Partnership for Research and Education in Plants (PREP; www.prep.biotech.
vt.edu), serves as a framework for determining the outcomes and impacts of authentic investigation and partnership.
PREP brings together high school teachers and research scientists to guide high school students in characterizing genes
in Arabidopsis thaliana. Scientists provide wild-type and mutant (T-DNA insertion line) seeds and experimental knowhow
to students, and students design and conduct experiments to examine the effects of abiotic stressors (e.g., drought,
salinity, soil pH, etc.) on wild-type vs. mutant plants, thereby helping to determine the function of each altered gene. We
are analyzing student lab reports to determine how students use their research questions to guide their experiment design,
data collection, and data analysis, as well as how students explain the implications of their findings.