Poster: Late and Moved Abstracts

Abs # 956: Transcriptional profiling at the onset of seed-fill during seed development in soybean.

Presenter:	Moskalenko, Oleksandr V., malex@purdue.edu
Authors	Moskalenko, Oleksandr V. (A)   Livingstone III, Donald S. (A)   Nielsen, Niels C. (B)
Affiliations:	(A): Purdue Universtiy (B): USDA Agricultural Research Service
Web Site:	http://www.agry.purdue.edu/nnlab

The transition from rapid cell division to cell expansion (seed-fill) reflects an important developmental shift that takes place during the formation of soybean seeds. Genetic events that occur at the time of this switch can be expected to influence the size of mature seeds and their composition. Amongst other things, the transition causes the normal mitotic cell cycle to be converted to an endoreduplication cycle. To identify genes whose expression changes with the appearance of the endo-cycle, large scale transcriptional profiling was performed using soybean seeds collected at 7 to 22 DAF (Days After Flowering). This interval was chosen because it appears to include the entire transition period. For this purpose, two-way Suppression Subtractive Hybridization (SSH) was performed between 14 DAF and 22 DAF cDNAs to create an 18,000 member library of SSH clones that encoded differentially expressed messages. A total of 2976 clones from these libraries were selected and used to generate a cDNA microarray. To collect the seed tissue required for target preparation, a seed length versus age study was carried out using the soybean variety Resnik. The microarrays were used to probe target RNA prepared from 7 DAF (1.09 mm), 14 DAF (3.17 mm), 18 DAF (5.02 mm) for 22 DAF (7.31 mm) seeds. Following microarray hybridizations and computation of relative transcription levels, quantitative PCR was used to validate results. DNA sequence analysis was carried out to identify genes that exhibit changes in transcription levels throughout the transition from cell division to cell expansion in soybean seeds.