Heat shock causes destabilization of specific mRNAs and destruction of endoplasmic reticulum in barley aleurone cells.
In response to a phytohormone, gibberellic acid, the aleurone layers of barley seeds synthesize and secrete alpha-amylases, which are coded by a set of stable mRNAs. When aleurone layers are subjected to heat shock treatment, the synthesis of alpha-amylase is suppressed while heat shock proteins are induced. The suppression of alpha-amylase synthesis is not the result of translational control as reported in several other systems. Rather, the sequences of alpha-amylase mRNA are rapidly degraded during heat shock as shown by in vitro translation and dot blot hybridization with a cDNA probe. Upon recovery from heat shock, the tissue resumes the synthesis of alpha-amylase in 2-4 hr. However, in the presence of a transcription inhibitor, cordycepin, the resumption of synthesis of alpha-amylase does not take place, indicating that new transcription of alpha-amylase genes is necessary for this recovery process. The degradation of alpha-amylase mRNAs correlates with the rapid destruction of endoplasmic reticulum as observed by electron microscopy, a phenomenon that has not been reported previously as a heat shock response. Since alpha-amylase mRNA is associated with the endoplasmic reticulum via membrane-bound polyribosomes, we suggest that the destruction of the endoplasmic reticulum during heat shock causes the destabilization and the eventual degradation of alpha-amylase mRNA.
D003839:Deoxyadenosines / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000648:ultrastructure; D004790:Enzyme Induction / Q000187:drug effects; D005875:Gibberellins / Q000494:pharmacology; D006360:Heat-Shock Proteins / Q000235:genetics*; D001467:Hordeum / Q000166:cytology / Q000378:metabolism; D006358:Hot Temperature; D012333:RNA, Messenger / Q000378:metabolism*; D013997:Time Factors; D014158:Transcription, Genetic; D000516:alpha-Amylases / Q000235:genetics / Q000378:metabolism
D003839:Deoxyadenosines; D005875:Gibberellins; D006360:Heat-Shock Proteins; D012333:RNA, Messenger; C007842:gibberellic acid; D000516:alpha-Amylases