Worm Breeder's Gazette 10(3): 27

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.

More Blue Worms

Steven Stone and Jocelyn Shaw

As described in the last issue of WBG, we are obtaining 
transformants with a plasmid containing the gene fusion, act-4  5'  
/lacZ/act-4  3' The aims of these experiments are to use expression of 
lacZ as a screen for transformed animals, and also to study the 
regulation of act-4 gene expression.
We have used our original transformed line to develop a reliable 
screen for transformants based on their ability to cleave the 
chromogenic substrate X-gal.  Briefly, the F2 progeny of injected 
worms are washed off their plates and permeabilized in a solution of 
5% SDS.  They are then washed and incubated in a staining solution 
containing X-gal at 25 C for 3-5 hours.  Worms containing the 
exogenous DNA turn strikingly blue while N2 nontransformed worms 
remain colorless.  The hermaphrodites are killed by the procedure but 
progeny eggs within them remain viable and are recovered.  Since 
developing the screen we have screened the F2 progeny of thirty 
injected worms.  From those injections we have obtained three 
independent transformed lines.  In one transformant the injected DNA 
has integrated into the genome, mapping to the X chromosome.  The 
other two transformants appear to have extra-chromosomal exogenous DNA 
based on the pattern of inheritance of lacZ expression in subsequent 
generations.  We have recently modified our original plasmid so that 
the chimeric gene lies between the inverted repeats of a Tc1 element.  
No transformed lines have been obtained, as yet, from this 
The pattern of expression of  -galactosidase transformants has been 
studied histochemically.  With the possible exception of the most 
recent transformant, the pattern of staining seems constant among the 
transformed lines.  When fixed adults are stained with X-gal, strong 
expression of lacZ appears to be tissue specific, with staining in 
body wall muscle and particularly vulval muscle and spermathaeca.  
There is expression in embryonic and larval animals as well, but it is 
not clear yet whether the adult tissue specificity applies to all 
developmental stages.  We also don't know whether act-4/lacZ is 
actually expressed in all tissues but is more highly expressed or more 
easily detected in these tissues.