Isolation and characterization of a genomic sequence of maize coding for a zein gene

Summary An EcoRI restriction endonuclease fragment of maize DNA coding for the 19,000 dalton zein protein was cloned in phage gt WES. The zein gene was identified by the electron microscopic analysis of RNA-DNA hybrids (R-loops) and DNA-DNA hybrids (D-loops). The R-loops were formed with poly(rA)-containing RNA isolated from 18 days post-pollination maize endosperm and showed no intervening non-hybridizing sequences (introns) within their 800 base length. A cDNA clone specific for the 19,000 dalton zein protein formed D-loops in the same position and orientation as the R-loops. The cloned fragment measured 4.4 kilobases (kb), the same size as an EcoRI fragment of maize DNA revealed by Southern analysis.