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

391 Characterization of the Sugar-Insensitive Mutants sis3, sis7 and sis8
Yadong Huang, Sue Gibson
University of Minnesota, Department of Plant Biology
Plants respond to environmental cues during seed germination and early seedling development. Sugar molecules,
as well as phytohormones, coordinate to control seed germination and seedling growth. It has been shown by our lab
and others that low to moderate concentrations of exogenous sugars (e.g. 30 mM sucrose) can delay seed germination in
wild-type Arabidopsis. High concentrations of sugars (e.g. 300 mM sucrose) in the media inhibit cotyledon expansion
and true leaf formation in wild-type seedlings. Several sugar insensitive (sis) mutants have been identified. Some of our
recent results on three of these mutants, sis7, sis3 and sis8, are presented here. The SIS7 gene was recently identified
using a map-based cloning approach and found to be the same as the NCED3 gene, which encodes 9-cis-epoxycarotenoid
dioxygenase, a key enzyme in the biosynthesis of abscisic acid. The sis7-1 mutant exhibits resistance to mannose and to
the gibberellin biosynthesis inhibitor paclobutrazol during seed germination. Genome wide transcriptional analyses of
the sis7-1 and sis7-2 mutants and several other sis mutants have been performed and the results of these analyses will be
described. The sis3 mutant shows wild type or near wild type responses in all phytohormone response assays conducted
to date. Another sis mutant, sis8, exhibits hypersensitivity to mannose and paclobutrazol. In addition, the morphology
of sis8 is distinct from the wild type. Identification of the SIS3 and SIS8 genes is in progress.
392 Arabidopsis Photomorphogenic Regulatory Network Discovery
Matthew Hudson, Kankshita Swaminathan, Stephanie Bellendir
University of Illinois, Urbana-Champaign
The transition between heterotrophic and autotrophic growth is orchestrated by a transcriptional regulatory network
under the control of photoreceptors. While immediate / early events that transduce signals from the phytochrome
photoreceptors to gene expression have been well studied, our understanding of the downstream transcriptional network
is limited. Using our own computational tools, we have identified new cis-regulatory DNA motifs from Arabidopsis
transcriptional profiling and genomic sequence data. We chose to focus on motifs specific to late responding light inducible
promoters, since these later events may be mediated by unknown regulatory pathways. Four novel motifs were identified
in the late responding, light inducible promoters. These motifs are capable of conferring light-inducibility on a reporter
gene in vivo. To elucidate the transcriptional regulatory effects of the pathways that regulate these elements, we have
constructed transgenic Arabidopsis lines that express the reporter gene luciferase under the control of these motifs. Results
from these experiments will be presented. In addition, we have used the output of the motif discovery software, including
the four late-response motifs, to develop a support vector machine model. Using this model, we are able to predict the
behavior of a large number of Arabidpsis light-induced genes in silico, based solely on the sequence of their promoters.
The annotation and prediction of gene expression from promoter sequence in Arabidopsis will be discussed.