Figure. PolyA+ RNA was prepared from 7 B-I and 7 B' plants at various developmental stages. The RNA was slot-blotted and probed with a B-specific probe. Each sample was loaded in duplicate, and approximately 0.5 micrograms of RNA was loaded into each well. The developmental stage of the plants is indicated along the side.
Understanding the alteration in expression
that leads to decreased pigmentation in B' plants might provide
clues as to the nature of the genetic alteration that occurs in the B-I/B'
heterozygote. As a first step, we have examined the difference in expression
in B-I and B' plants. We isolated polyA+ RNA from husks of
B-I and B' plants of various ages. These RNA samples were
slot-blotted onto nitrocellulose and probed with a B-specific probe.
We find that B-I plants have 20-100 fold more B mRNA than
B' plants at each age examined, as shown in the figure. Northern
blot analysis demonstrated that the B polyA+ transcripts are the
same size in B-I and B' plants. These same B-I husks
have accumulated 20-100 fold more anthocyanin pigment than B' husks.
Pigment accumulation was measured by acid extraction and spectrophotometric
determination of anthocyanin concentration. The same slot blot was stripped
and reprobed with A1 and Bz1 probes (A1 and Bz1
are structural genes induced by B in husk tissue). The B-I
husks also have much more mRNA from these loci. These results demonstrate
that the difference in pigmentation and structural gene induction between
B-I and B' correlates with a difference in mRNA accumulation.
Experiments are in progress to determine if there are differences in transcription
of the two alleles.
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