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

399 Identification and Characterization of Sugar-Response Genes by Genomics and Reverse
Genetics in Arabidopsis
Chunyao Li, Tim Heisel, Sue Gibson
Department of Plant Biology, University of Minnesota
Sugars play a critical role in modulating plant development, metabolism and gene expression. In addition, sugarresponse
pathways are thought to help regulate allocation of fixed carbon between source and sink tissues, and so play
an important role in carbon partitioning and, ultimately, crop yields. Sugar signaling networks are also found to interact
with phytohormone signaling networks, such as those regulated by abscisic acid, ethylene and gibberellins. Despite the
importance of sugar-response pathways, only a small percentage of the components predicted to act in these pathways
have been identified so far. We are employing an approach combining genomics and reverse genetics to identify and
characterize genes that are involved in sugar response pathways. By analyzing Affymetrix GeneChip data we selected 189
glucose- and/or sucrose-regulated genes that are predicted to encode proteins with activities commonly associated with
response pathways, such as transcription factors, protein kinases and protein phosphatases. We then identified T-DNA
insertion lines that are homozygous for insertions in most of these 189 target genes. Currently we are screening these
T-DNA insertion lines for defects in any of several sugar responses. To date we have identified two mutants, sov1 and
hac1, that show altered sensitivity to the inhibitory effects of high concentrations of exogenous sugars on early seedling
development. The sov1 mutant exhibits a hypersensitive response to the inhibitory effects of both sucrose and glucose
during seed germination and early seedling development. In addition, sov1 is hypersensitive to the phytohormone abscisic
acid. The hac1 mutant exhibits weak insensitivity to sucrose during seed germination and early seedling development.
In addition to sov1 and hac1, we have also found that several other mutants exhibit alterations in sugar-regulated gene
expression by real-time PCR analysis.
400 Light regulation of gene expression in soybean
Ying Li, Matthew Hudson
University of Illinois at Urbana-Champaign
Photomorphogenesis is relatively well understood in model systems like Arabidopsis. For example, the expression
profiles of genes response to light signals in Arabidopsis have been examined in detail, using oligonucleotide microarrays.
However, although the importance of photomorphogenic effects on crop morphology, physiology and yield are undoubted,
photomorphogenic effects in crop plants are under-researched. In our study, we focused on the transcriptional regulation of
photomorphogenesis in soybean using microarrays and real-time PCR. We used the soybean cDNA microarray developed
by the NSF Soybean Functional Genomics project to find genes whose expression changes rapidly in etiolated soybean
seedlings in response to a pulse of far red light. We then used published Arabidopsis microarray data to translate existing
knowledge of photomorphogenesis into a better understanding of the mechanism of light-regulated development and signal
transduction in soybean, and the natural variation in this process between soybean and Arabidopsis. We computationally
determined the orthologous relationships between the genes represented on the NSF soybean cDNA microarray and the
Arabidopsis oligonucleotide array, and compared the phytochrome regulated networks in soybean and Arabidopsis. Our
results show that although some of the light regulated genes in the soybean microarray have orthologs in Arabidopsis, many
are unique to soybean, suggesting overlapping and yet distinct transcriptional networks controlling photomorphogenesis
in the two plant species. Results from this analysis will be presented.