Posttranscriptional regulation of α-amylase II-4 expression by gibberellin in germinating rice seeds

• Published in: Plant physiology and biochemistry 2004-06, Vol.42 (6), p.477-484
• Main Authors: Nanjo, Yohei, Asatsuma, Satoru, Itoh, Kimiko, Hori, Hidetaka, Mitsui, Toshiaki, Fujisawa, Yukiko
• Format: Article
• Language: English
• Subjects: Aleurone; alpha-Amylases - genetics; Base Sequence; Biological and medical sciences; Blotting, Northern; Ca 2; Calmodulin; Cell physiology; DNA Primers; Fundamental and applied biological sciences. Psychology; G protein; Gene Expression Regulation, Developmental - physiology; Gene Expression Regulation, Enzymologic - physiology; Gene Expression Regulation, Plant - physiology; Germination; Gibberellin; Gibberellins - metabolism; Molecular and cellular biology; Mutation; Oryza - drug effects; Oryza - enzymology; Oryza - genetics; Oryza - growth & development; Reverse Transcriptase Polymerase Chain Reaction; Rice; RNA Processing, Post-Transcriptional - genetics; Signal transduction; α-Amylase
• ISSN: 0981-9428; 1873-2690
• DOI: 10.1016/j.plaphy.2004.04.005

Hormonal regulation of expression of α-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 α-amylase II-4 in the aleurone layer were essentially identical to those of α-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 α-amylase II-4 was also similar to that of α-amylase I-1. However, the level of α-amylase II-4 mRNA was not increased by gibberellin, indicating that the transcriptional enhancement of α-amylase II-4 expression did not occur in the aleurone. Gibberellin stimulated the accumulation of 45Ca 2+ into the intracellular secretory membrane system. In addition, several inhibitors for Ca 2+ signaling, such as EGTA, neomycin, ruthenium red (RuR), and W-7 prevented the gibberellin-induced expression of α-amylase II-4 effectively. While the gibberellin-induced expression of α-amylase II-4 occurred normally in the aleurone layer of a rice dwarf mutant d1 which is defective in the α subunit of the heterotrimeric G protein. Based on these results, it was concluded that the posttranscriptional regulation of α-amylase II-4 expression by gibberellin operates in the aleurone layer of germinating rice seed, which is mediated by Ca 2+ but not the G protein.