Sequence analysis of zein cDNAs obtained by an efficient mRNA cloning method

Area of Science:

• Molecular Biology
• Plant Science
• Genetics

Background:

• Zein proteins are the primary storage proteins in maize (Zea mays) endosperm.
• Understanding zein gene structure and expression is crucial for improving maize nutritional value and yield.

Purpose of the Study:

• To develop an improved method for constructing cDNA libraries from maize endosperm mRNA.
• To analyze the DNA sequences of zein subfamily cDNAs to elucidate gene structure and transcription regulation.

Main Methods:

• Isolation of mRNA from developing W22 maize inbred endosperm.
• Construction of a novel cDNA library using oligo-dT and oligo-dG tailing with pUC9 plasmid.
• Alkaline sucrose gradient centrifugation for cDNA separation.
• DNA sequencing of zein cDNA clones.
• Colony hybridization screening using labeled probes.

Main Results:

• Detailed DNA sequences of four zein subfamily cDNA clones were determined.
• Genes for larger zein species contain eleven repeat units, differing from the previously known nine.
• Transcription termination occurs at two distinct polyadenylation signals.
• Transcription initiation site identified 31 base pairs downstream of the TATA box.

Conclusions:

• The novel cDNA library construction method is effective for analyzing maize endosperm transcripts.
• Zein gene structure exhibits variations in repeat units, impacting protein size.
• Multiple polyadenylation signals and a specific transcription start site influence zein gene expression regulation.