Carbohydrate starvation stimulates differential expression of rice alpha-amylase genes that is modulated through complicated transcriptional and posttranscriptional processes.
Expression of alpha-amylase genes in cultured rice suspension cells is induced by sucrose starvation. To study the mechanism of sugar metabolite regulation on the expression of individual alpha-amylase genes, DNA fragments specific to each of eight rice alpha-amylase genes were synthesized and used as gene-specific probes. Comparison of the relative abundance of mRNA revealed that expression of the eight alpha-amylase genes in rice cells was differentially regulated by sucrose starvation. Accumulation of all the alpha-amylase mRNAs increased in response to sucrose starvation; however, levels of the alphaAmy3 and alphaAmy8 mRNAs were distinctly higher and constituted 90% of total alpha-amylase mRNAs. RNA gel blot and nuclear run-on transcription analyses demonstrated a positive correlation between the increased transcription rates and the elevated steady-state levels of alpha-amylase mRNAs induced by sucrose starvation. The half-lives of alphaAmy3, alphaAmy7, and alphaAmy8 were prolonged by sucrose-starvation; however, the stability of the three mRNAs seems controlled by different mechanisms. The translation inhibitors cycloheximide and anisomycin preferentially blocked the sucrose-suppressed expression of alphaAmy3 but not that of alphaAmy7 and alphaAmy8. These inhibitors also enhanced the sucrose starvation-induced accumulation of alphaAmy3 mRNA but not that of alphaAmy7 or alphaAmy8 mRNAs. Cycloheximide did not significantly alter the transcription rates of alpha-amylase genes, suggesting that labile proteins may selectively stabilize the alphaAmy7 and alphaAmy8 mRNAs but destabilize the alphaAmy3 mRNA.
Sheu
J J
JJ
Institute of Molecular Biology, Academia Sinica, Nankang, Taipei 11529, Taiwan, Republic of China.
Yu
T S
TS
Tong
W F
WF
Yu
S M
SM
D000841:Anisomycin / Q000494:pharmacology; D001483:Base Sequence; D002478:Cells, Cultured; D053938:DNA Fragmentation; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D012275:Oryza / Q000166:cytology / Q000201:enzymology*; D014176:Protein Biosynthesis / Q000187:drug effects; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid; D013395:Sucrose; D014158:Transcription, Genetic; D000516:alpha-Amylases / Q000235:genetics*
D012333:RNA, Messenger; D013395:Sucrose; D000841:Anisomycin; D000516:alpha-Amylases