Abstract
We have cloned gibberellin (GA) 3β-hydroxylase cDNA, (HvGA3ox), a homolog of the rice gene OsGA3ox from germinating barley seeds. HvGA3ox cDNA was expressed in Escherichia coli capable of oxidizing GA9 to GA4 and GA20 to GA1. Deduced amino acid sequence analysis showed that HvGA3ox was identical to HvGA3ox2 reported by Spielmeyer et al. (2004). Northern analysis showed that HvGA3ox2 was expressed only in germinating seeds, not in other organs. Typical feedback regulation was not observed in seedling treated with either GA3 or uniconazole. HvGA3ox2 mRNA was detected from 12 hours after imbibition just before the expression of a-amylase gene, Amy1. In situ hybridization of germinating seeds revealed that HvGA3ox2 mRNA was localized in the epithelium. Our results suggest that GA biosynthesis in epithelium is important for the expression of α-amylase in germinating barley seeds, and HvGA3ox2 encodes the key enzyme of this event.
