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.
Institute of Molecular Biology, Academia Sinica, Nankang, Taipei 11529, Taiwan, Republic of China.
J J
JJ
Sheu
T S
TS
Yu
W F
WF
Tong
S M
SM
Yu
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