Implications of expansin-like 3 gene in Dictyostelium morphogenesis.

Dictyostelium harbors multiple expansin-like genes with generally unknown functions. Thus, we analyzed the expansin-like 3 (expL3) gene and found that its expression was reduced in a null mutant for a STATa gene encoding a transcription factor. The expression of expL3 was developmentally regulated and its transcript was spliced only in the multicellular stages. The expL3 promoter was activated in the anterior prestalk region of the parental strain and downregulated in the STATa null slug, although the expL3 promoter was still expressed in the prestalk region. The expL3 overexpressing strain exhibited delayed development and occasionally formed an aberrant structure, i.e., a fruiting body-like structure with a short stalk. The ExpL3-myc protein bound cellulose.