1. Section of Plant Biology, Cornell University, Ithaca, New York 14853
2. Computational Biology Service Unit, Cornell University, Ithaca, New York 14853
3. Department of Developmental Genetics, University of Wyoming, Laramie, Wyoming 82071
4. Plant Gene Expression Center, U.S. Department of Agriculture-Agricultural Research Service, Plant and Microbial Biology Department, University of California at Berkeley, Berkeley, California 94720