Gibberellic acid (GA3)-induced enhancement of alpha-amylase activity in the aleurone of shrunken-2 maize kernels
1994
Sanwo, M.M. | DeMason, D.A.
The aleurone of RB-3 shrunken-2 (sh2) maize kernels is deficient in alpha-amylase activity during germination, but exogenous applications of gibberellic acid (GA3) (0.001-10 micromolar) induced low levels of activity. The highest activity was measured in the aleurone of kernels treated with 10 micromolar GA3 (14,600 +/- 945 units), but was lower than untreated Starchy (Su) aleurone tissues (35,280 +/- 5,010 units). On isoelectric focusing gels, no alpha-amylase isozymes were detected in the untreated sh2 aleurone using starch zymograms or immunoblots, but the 1.0 and 10 micromolar GA3 treatments induced nearly all the isozymes (eight to ten) present in the Su aleurone. There was a very low level of alpha-amylase mRNA in the untreated sh2 aleurone, an intermediate level in the 1.0 micromolar GA3-treated sh2 aleurone, and the highest level in the untreated Su aleurone. On the confocal microscope, the 1.0 micromolar GA3-treated aleurone cells had enhanced levels of cytoplasmic membranes and RNA compared to untreated sh2 aleurone cells. The 1.0 micromolar GA3 treatment also induced shoot elongation in the sh2 seedlings. The data demonstrate that the sh2 aleurone is deficient in its function to produce alpha-amylases, and exogenous GA3 can partially restore cell function in the sh2 kernels.
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