Poster: Regulation of gene expression

Abs # 768: Gene expression programs on different pathways leading to shoot, callus and root development in Arabidopsis tissue culture

Presenter:	Che, Ping , pche@iastate.edu
Authors	Che, Ping  (A)   Lall, Sonia  (A) (A)  Howell, Stephen H (A)
Affiliations:	(A): Iowa State University Plant Sciences Institute

Ping Che, Sonia Lall and Stephen H. Howell Plant Sciences Institute Iowa State University, Ames Iowa 50011 The balance of plant hormones, cytokinin and auxin, acts as a switch to direct regeneration in Arabidopsis tissue culture along different developmental paths leading to the formation of shoots, callus or roots. The expression programs underlying these different developmental programs differ in the expression of hundreds of genes, and the genes encoding transcription factors or signaling components that are specifically expressed in one developmental pathway, but not the others, were identified. During shoot development, genes such as At5g13330, encoding a putative Rap2.6-like, AP2-domain transcription factor, and At3g48100, encoding ARABIDOPSIS RESPONSE REGULATOR5, ARR5, were highly upregulated, but not during the formation of callus or roots. T-DNA knock-outs of these two genes showed opposite regeneration phenotypes. Rap 2.6-like, AP2-domain transcription factor mutants showed severely impaired shoot formation, but ARR5 mutants showed enhanced shoot formation. The impact on global gene expression in these mutants was further studied with Affymetrix 20K gene oligoncleotide arrays. Genes upregulated during shoot formation and constituting the early shoot induction medium (SIM) regulon were identified, and the promoters of genes in the regulon were scanned for common sequence motifs.