Worm Breeder's Gazette 10(3): 86

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

A Paraquat Sensitive Mutant, mev-1

Naoaki Ishii, Kiyoko Takahashi, Satoru Tomita, Tetsuo Keino and Kenshi Suzuki

There is an attractive idea that active oxygen species act as a 
promoter of aging.  In order to get knowledge on the relationship 
between active oxygen species and aging, we isolated mutants which are 
hypersensitive to paraquat (methylviologen).  This is a herbicidal 
drug and is known to yield superoxide anion (O2-).  
First screening to isolate paraquat sensitive 
N2 hermaphrodites were mutated with EMS.  F2 progenies having eggs 
were treated with 30mM paraquat for 4 hr and inactive worms were 
separated onto small spotted NG agar plates.  Paraquat sensitive F2 
animals must die, but the eggs were expected to survive because 
paraquat does not enter into unhatched eggs in mother, while paraquat 
resistant wild animals and the hatched larvae must survive altogether.
Young adult worms were hypochlorited to isolate eggs.  The eggs were 
washed with M9 buffer and resuspended in S buffer.  Next day the 
hatched starved L1 larvae were transferred to NG agar plate including 
2 mM paraquat and three days later survivors were scored as animals 
which had developed into L4 larvae or adults.  
One of these mutants, mev-1, was investigated for its properties.  
It was found that mev-1 is about four times more sensitive to this 
drug than the wild type.  Preliminary experiments showed that mev-1 
was also more sensitive to exposure to oxygen gas and to Cr(-6).  Mev-
1 was found to have a shorter life span as compared with that of the 
wild type.  Namely, the half-life for mev-1 was 8 days at 20 C, while 
the half-life for the wild type was 12.5 days.  It was found that the 
level of superoxide dismutase (SOD) of mev-1 was about half the level 
of the wild type.  The mev-1 gene was found to be located on linkage 
group III and fine mapping is in progress now.  
It is suggested that superoxide anion of which the level in normal 
cell is delicately controlled by SOD, however the exceeding superoxide 
anions or lack of SOD must cause cell damages and reduce the life span.