THE PLANT CELL, Vol 2, Issue 11 1039-1049, Copyright © 1990 by American Society of Plant Biologists
Bronze-2 Gene of Maize: Reconstruction of a Wild-Type Allele and Analysis of Transcription and Splicing
J. Nash, K. R. Luehrsen and V. Walbot
Department of Biological Sciences, Stanford University, Stanford, California 94305-5020
The maize Bronze-2 (Bz2) gene, whose product acts late in the anthocyanin
biosynthetic pathway, has been cloned and its transcript has been mapped.
We have developed a general procedure for reconstructing wild-type alleles
from transposable element-induced mutants. An existing
transposon-containing clone, bz2::mu1 [McLaughlin, M., and Walbot, V.
(1987). Genetics 117, 771-776], was modified by replacing the region of
bz2::mu1 containing the transposon with the corresponding polymerase chain
reaction-amplified sequence from the progenitor allele that has no Mu
insertion. Particle gun delivery of the reconstructed Bz2 gene to embryonic
scutellar tissue lacking a functional Bz2 gene complemented the bz2 mutant
phenotype, as demonstrated by the production of purple spots. Having cloned
the wild-type allele, we then analyzed the Bz2 transcript, whose features
include an 82-nucleotide 5[prime] -untranslated leader, one small intron
(78 base pairs) within the coding region, and multiple polyadenylation
sites. Four Mutator transposon insertions that eliminate gene function were
mapped within the 850-nucleotide transcription unit. We found that variable
levels of unspliced Bz2 RNA are present in purple husk tissue; this finding
may indicate that the expression of Bz2 is regulated in part at the level
of transcript processing.
