J. Biol. Chem., Vol. 265, Issue 17, 9652-9658, 06, 1990
Analysis of seed storage protein genes of oats
MA Shotwell, SK Boyer, RS Chesnut and BA Larkins
Department of Plant Sciences, University of Arizona, Tucson 85721.
We have isolated genomic clones encoding the two major classes of seed
storage proteins in oats, the 12 S globulins and the avenins. The globulin
genes encode glutamine-rich, sulfur-poor storage proteins that are highly
conserved in sequence and structure. The globulin genes contain three short
introns whose positions in the coding sequence are the same as in storage
globulin genes in legumes and other dicots. The avenin genomic clone
contains four tightly linked genes that belong to both of the two avenin
gene subfamilies. The avenin genes encode glutamine-rich, lysine-poor
proteins that vary in length due to differences in the number of peptide
repeats. Although globulin and avenin genes are expressed coordinately
during oat seed development, their promoter regions do not contain any
conserved sequence elements that might determine developmental timing.
Previous studies showed that there are roughly equal amounts of globulin
and avenin mRNAs in developing oat seed, despite there being much more
globulin than avenin in mature seed. Storage protein synthesis in oats must
therefore be controlled partially by post-transcriptional mechanisms.
Sequence analysis of globulin and avenin genes has provided several clues
as to why globulin mRNAs may be translated more efficiently than avenin
mRNAs.