Posttranscriptional regulation of alpha-amylase II-4 expression by gibberellin in germinating rice seeds.
Hormonal regulation of expression of alpha-amylase II-4 that lacks the gibberellin-response cis-element (GARE) in the promoter region of the gene was studied in germinating rice (Oryza sativa L.) seeds. Temporal and spatial expression of alpha-amylase II-4 in the aleurone layer were essentially identical to those of alpha-amylase I-1 whose gene contains GARE, although these were distinguishable in the embryo tissues at the early stage of germination. The gibberellin-responsible expression of alpha-amylase II-4 was also similar to that of alpha-amylase I-1. However, the level of alpha-amylase II-4 mRNA was not increased by gibberellin, indicating that the transcriptional enhancement of alpha-amylase II-4 expression did not occur in the aleurone. Gibberellin stimulated the accumulation of 45Ca2+ into the intracellular secretory membrane system. In addition, several inhibitors for Ca2+ signaling, such as EGTA, neomycin, ruthenium red (RuR), and W-7 prevented the gibberellin-induced expression of alpha-amylase II-4 effectively. While the gibberellin-induced expression of alpha-amylase II-4 occurred normally in the aleurone layer of a rice dwarf mutant d1 which is defective in the alpha subunit of the heterotrimeric G protein. Based on these results, it was concluded that the posttranscriptional regulation of alpha-amylase II-4 expression by gibberellin operates in the aleurone layer of germinating rice seed, which is mediated by Ca2+ but not the G protein.
Nanjo
Yohei
Y
Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan.
Asatsuma
Satoru
S
Itoh
Kimiko
K
Hori
Hidetaka
H
Mitsui
Toshiaki
T
Fujisawa
Yukiko
Y
D001483:Base Sequence; D015152:Blotting, Northern; D017931:DNA Primers; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D018525:Germination; D005875:Gibberellins / Q000378:metabolism*; D009154:Mutation; D012275:Oryza / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D012323:RNA Processing, Post-Transcriptional / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000516:alpha-Amylases / Q000235:genetics*
D017931:DNA Primers; D005875:Gibberellins; D000516:alpha-Amylases