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GENE EXPRESSION CHANGES IN EARLY CERATOPTERIS RICHARDII SPORE DEVELOPMENT.  M.L. Salmi, S.C. Stout and S.J. Roux.  Section of Molecular Cell and Developmental Biology.  University of Texas at Austin.  Austin TX 78712.

   As an approach to understanding the cellular basis of gravity responses, we are using germinating spores of the fern Ceratopteris richardii. Gravity determines the developmental polarity of the single celled spore, and does so within the first 24 h after the cell is induced by light to begin its germination. A major benefit of this system is that both gravity sensing and gravity response occur in the same cell.  We are using microarrays to examine differential gene expression between spores grown in microgravity and 1g. 

   Microarrays were printed with 3,072 randomly chosen cDNAs. These microarrays are being used to evaluate the pattern of gene expression over the first 24 h of spore development, the time in which spores are emerging from dormancy and determining polarity. Within the first 24 h about 1% of genes on the microarray are differentially expressed at least 2.5 fold. In a comparison of spores at 12 h after germination verses 24 h after germination, a Peroxidase gene was 4-5 times more abundant in the latter developmental stage. During the same period an NidD Aldolase gene was decreased 4 fold. Genes implicated in early spore development will be knocked out via RNA interference to evaluate their role in normal spore germination. Once 1g gene expression patterns have been determined, the microarray will be used to evaluate changes in gene expression of spores developing in microgravity (from STS-93) compared with spores developing in 1g.

(Supported by NAG10-0295 and NAG2-1347 to SJR)