Bass, H W; Goode, J H; Greene, T W; Boston, R S. (1994)
Control of ribosome-inactivating protein (RIP) RNA levels during maize
seed development. Plant Science v101(1):17-30.
ABSTRACT:
The maize RIP1 gene encodes proRIP, the zymogen form of a
ribosome-inactivating protein that accumulates to high levels in
endosperm. ProRIP is synthesized coordinately with the major storage
proteins and requires a functional allele of the transcriptional
activator, Opaque-2 (O2)-3 for maximal accumulation. RIP1 gene expression
was characterized by developmental RNA gel blot analysis. RIP1 RNA was
first detected at 10 days after pollination (DAP), and increased in
abundance to reach maximal levels at mid-maturation of the kernel. In four
W64A maize lines with independently-derived opaque-2 (o2) alleles, RIP1
RNA still accumulated in a developmentally specific pattern, but showed
qualitative and quantitative changes from normal. RNA gel blots reprobed
with an O2-specific probe provided evidence for coordinate accumulation of
RIP1 and O2 RNAs throughout normal kernel development. The pleiotropic
endosperm mutations brittle-1 (bt1), brittle-2 (bt2), shrunken-2 (sh2),
sugary-2 (su2), Mucronate (Mc), Defective endosperm-B30 (De*-B30), and
floury-2 (fl2), affected RIP1 and O2 RNA accumulation to varying degrees.
None of these mutations, however, resulted in RIP1 RNA reductions
comparable to that seen in W64Ao2. When coupled with o2, bt1 and bt2
mutations showed synergistic interactions in their effects of reducing
RIP1 RNA levels. Thus, RIP1 gene expression and relative RNA levels are
controlled by multiple factors including O2, an O2-independent
mutations.
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