Isolation of a gene encoding a glycosylated cytokinin oxidase from maize.
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Resumo
The major cytokinin oxidase in immature maize kernels was purified to homogeneity. Selected tryptic peptides were used to design degenerate oligonucleotide primers for PCR isolation of a fragment of the oxidase gene. Hybridization of the PCR fragment to a maize genomic library allowed isolation of a full-length cytokinin oxidase gene (ckx1). The gene encodes a protein of approximately 57 kDa that possesses a signal peptide, eight consensus N-glycosylation sequences and a consensus FAD binding sequence. Expression of ckx1 in Pichia caused secretion of active glycosylated cytokinin oxidase that contains a substrate-reducible FAD. The gene displays sequence homology with a putative oxidoreductase from Arabidopsis thaliana and with the fas5 gene from Rhodococcus fascians.