PLANT PHYSIOLOGY , Vol 102, Issue 1 195-203, Copyright © 1993 by American Society of Plant Biologists
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MOLECULAR BIOLOGY AND GENE REGULATION |
Aleurones from a Barley with Low [alpha]-Amylase Activity Become Highly Responsive to Gibberellin When Detached from the Starchy Endosperm
R. W. Skadsen
United States Department of Agriculture, Agricultural Research Service, Cereal Crops Research Unit, 501 North Walnut Street, Madison, Wisconsin 53705
The physiological and molecular bases for contrasting [alpha]-amylase
phenotypes were examined in germinating seeds of two barley (Hordeum
vulgare L.) cultivars, Morex and Steptoe. Morex is a high-quality malting
barley that develops high [alpha]-amylase activity soon after germination.
Steptoe is a feed barley that develops only low [alpha]-amylase activity
levels during this period. The expression of all high- and low-isoelectric
point (pl) [alpha]-amylase isozymes is reduced in Steptoe. The amount of
[alpha]-amylase mRNA per gram of seedling tissue is correspondingly lower
in Steptoe. Southern blot analysis revealed that the cultivars have the
same copy number and organization for most high- and low-pl genes. Steptoe
seedlings or embryoless half-seeds produce little [alpha]-amylase in
response to exogenous applications of gibberellic acid (GA3) compared with
Morex. However, when isolated aleurones of both cultivars are treated with
GA3, they produce similar amounts of high- and low-pl [alpha]-amylase RNAs.
This suggests that a factor in the starchy endosperm is responsible for
lowered [alpha]-amylase response in Steptoe. The factor is probably not
abscisic acid (ABA), since the two cultivars have similar concentrations of
ABA during germination.