ANALYSIS OF ZEIN GENE EXPRESSION IN DEVELOPING MAIZE ENDOSPERM (POLYADENYLATION, REGULATION, STORAGE PROTEIN)
Abstract
To characterize the heterogeneity of zein mRNA a cDNA library was constructed. Clones from this library, which were of sufficient size to be full-length or near full-length copies of their corresponding mRNA, were characterized by restriction enzyme mapping, cross-hybridization analysis, and DNA sequencing. Based on these analyses nine different classes of zein sequences were distinguished. These were a single class of Mr 15,000 sequences, five classes of Mr 19,000 sequences and three classes of Mr 22,000 sequences. Each of the three Mr 22,000 zein groups are 60% to 70% homologous to each of the Mr 19,000 zein groups. Sequences within the Mr 22,000 zein groups showed 92% homology, and sequences within the Mr 19,000 groups showed homology ranging from 75% to 95%. The Mr 15,000 zein sequences showed no homology to those for either the Mr 19,000 or Mr 22,000 zeins. Representative clones from these nine groups were used as probes in hybridization experiments to measure the levels of mRNA from developing maize endosperms. It was found that the groups are represented by varying amounts of mRNA that range from 2% to 20% of the total zein mRNA population. For the Mr 19,000 and Mr 22,000 zein clone groups there is a correlation between the percentage of transcripts in the mRNA population representing a clone group and the apparent number of genes for that group in the maize genome (as determined by Southern blot hybridization analysis). For instance, a clone group represented by 2% of the transcripts is only represented in the maize genome by 1 or 2 copies, whereas, a clone group represented by 20% of the transcripts is represented in the maize genome by 10 to 15 copies. This correlation suggests that these genes are transcribed to nearly the same extent during endosperm development. An exception to this is the Mr 15,000 zein clone group. This group represents 6% of the endosperm transcripts but is only present in the maize genome in 1 or 2 copies. This suggests that it is transcribed at a higher rate during endosperm development or that its transcripts are more stable.
Degree
Ph.D.
Subject Area
Genetics
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.