A combination of a single stranded plasmid vector and ordered deletions were used to determine the complete nucleotide sequence of a rDNA spacer region isolated from the DNA of maize Black Mexican Sweet suspension cells. The sequence reveals the presence of ten "200 base" subrepeats within the maize rDNA spacer region. By S1 protection experiments we have tentatively determined that the start of maize rRNA transcription is 144 bases 3' of the end of the last spacer subrepeat. We propose that the spacer subrepeats may have an important role in regulating maize rRNA transcription.

The protein sequence of a representative of the zeins, the major storage proteins of maize, has been derived from the nucleotide sequence of a zein cDNA clone. This cDNA was sequenced both by the Maxam and Gilbert and the M13-dideoxy techniques. The nucleotide sequence encompasses the non-translated 3' terminus of the mRNA, the entire coding sequence specifying both the mature zein protein and a small signal peptide, and a portion of the non-translated 5' region. The deduced amino acid composition and the amino-terminal amino acid sequence closely resemble those derived from chemical analysis of the zein protein fraction. The data presented represent the first complete amino acid sequence of a plant storage protein.

No abstract

No abstract

We have isolated several Zea mays cDNAs encoding the 40S subunit ribosomal protein S14. In maize, this ribosomal protein is encoded by a small multigene family, at least three members of which are expressed. S14 transcript levels are highest in mitotically active tissues, such as seedling shoot, developing endosperm, and tassel primordia, and lowest in tissues with little cell division, such as mature leaf and root. Very little S14 RNA is present in pollen, suggesting that translation of pollen mRNAs during pollen germination uses preformed ribosomes. During kernel development, the highest levels of S14 transcripts in endosperm tissue are found at 10-12 days postpollination; S14 RNA levels decline continuously from this point onward. The period of maximal expression of the S14 ribosomal protein gene appears to precede the onset of storage protein synthesis and does not correlate with the reported times of increased nucleolar volume or genome amplification.