SPERM-EGG INTERACTING SUBSTANCES, III 53 



mutants to produce wo-rhamnetin is due to their inability to 



OCR 



OH O 



Z50-Rhamnetin 



synthesize the intracellular precursor of this substance, quercetin. 

 In the presence of added quercetin they can produce wo-rhamnetin 

 and then become able to copulate with male gametes. Clone 2 is 

 a homothallic strain which normally produces female and male 

 gametes. When Clone 2 cells are treated with peonin or 4-hydroxy- 

 ^-cyclocitral, which induce male characteristics, all of them 

 copulate with female cells if these are available; if, however, 

 homothallic cells are treated with wo-rhamnetin, which induces 

 female characteristics, all of them pair with male cells. Clone 3 

 consists of normal male cells. 



OCH, 



HO 



OH 



Y"-^^o^ 



HjC CH, 



"\ V CHO 



O 



I 



elucose 



glucose 



H— C 



\/-/^\. 



/ ^C' 



OH /\ 

 H H 



Peonin 



CH, 



4-hydroxy-^- cyclocitral 



When a solution is believed to contain quercetin, it is added to 

 a suspension of Clone i ; if quercetin is present, the Clone i cells 

 produce wo-rhammetin. Clone 2 cells are then treated with the 

 solution containing /^o-rhamnetin. This causes them to react as 

 female cells so that Clone 3 cells will copulate with them. The test 

 procedure can therefore be summarised as follows: 



Test solution — > Clone i — > Clone 2 < — Clone 3 



If Clone 3 cells copulate with Clone 2 cells, quercetin is present in 

 the test solution. 



As often happens, other scientists have been unable to con- 

 firm Moewus' findings. Lewis (1954, p. 266), for example. 



