mRNAs that don't go away

Lorraine Sohlberg drayage at EARTHLINK.NET
Thu Jun 26 10:34:58 EST 1997


I have gotten some odd results when localizing a mRNA in a senescing 
tissue and was wondering if you have seen anything similar in 
senescing leaves or other tissues.  I have localized the mRNA encoding 
an endopeptidase which degrades seed storage protein in cotyledons of 
bean during germination. 

My observation is that the endopeptidse mRNA remains at high levels 
even in cells that appear to be collapsed and have very little 
cytoplasm and have been thought to be dead due to their lack of 
staining with tetrazolium which detects activity of basic enzymes of 
respiration. It is strange to me that this message would not be 
degraded by RNAses in the senescing cells. Have you observed any long 
lived mRNAs in senescing cells? Do you know of anyone else doing work 
on senescing tissues who might have observed patterns of RNA 
accumulation?

I had known from Northerns that this message was abundant in 
cotyledons that were shriveled and depleted of storage protein, but I 
did not expect the message to be concentrated in the cells which 
appeared collapsed.

This endopeptidase appears to be specific to the senescing cotyledon 
in bean. I had been curious if this endopeptidase would also be 
expressed in senesing leaves, nodules and pods and did westerns and 
northern blots on samples from these tissues and did not see any 
expression.



If you have any ideas, please e-mail or call me. 

Thanks, Lorraine Sohlberg, lorraine at nature.berkeley.edu



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