October 7, 1953

Dear Dr. Rizet:

We have been folowing your work on Podospora with the greatest
interest. I hope you will continue to favor me with reprints dealing
with it.

Our labo. group recently held a seminar, during which some questions
came up that I ask to bring to your attention, I would not exclude the
possibility that they have been dealt with your two reviews (Rev.
Cytol. Biol. Veg. 1949 and 1952), and I hope| that, if so, you will
forgive our overlooking this.

 
  
  

In connection with the formation
+/-, should any serious attention be given, o
gular (atypical) r

typically dikaryotic
possibility that
ction of the centro-
nh once suggestéd that a amall

          
   
   
  
  
  
 

  

mere at the first division.
para-centric inversion might s
a¢ ySuch an inversion might also
omere and the marker]. This
vs the assumption of a regular,
thé Only criterion I can visualize at
j\aarker on the "sex"—chromosome which
showing that the centromere (or some

hypothesis is, a préori, no less atte
single crossover near the cpntromere.
the instant would be the be e
did show regular first—di
point at least) mst do

\
We were especially rested in tHe barrage results [e.g. in view of pos-
sible connections with thi ective’F+ factor in E. coli:: I hope Professor

    
  
  

Ephrussi will ha orwarded “to you addrgssed under cover to him].
If I understand 7 onelusion;-it is that the s produced from crosses of
S x 8 obtain age of some "plasmid" from S to s. However, you note

that the resh}{t is the safe regardless of the sexual polarity (with respect to

ascogonia/spekmatia) of thé cross, while the results of s x s are affected by
x. wever that you emphasize that it is the issue of the

Ss heterozygotes ay show the s* type, so perhaps I have oversimplified your

would be mech more readily compatible with a slightly different scheme, your
views on which [if not already given] would be of eon&éderable interest here:

Let us assume that it is 3 (rather than S) which carries a plasmid g, and that
f is in jf a sense essentially inviable in the presence of the S gene. The s5
genopype would #gk then differ from the originalxx s in completely lor im view
of occasional spontaneous reversions] st completely] lacking 4. This might
be comparable to the relationship s ppa not to K but to other "sensitivity
genes" in Paramedium. Alterngtavély, S might carry an alternative plasmid g
which competes against 4 it Sata Esag type, but this is a needless miltiplication
pf particles. To explain raion, one mist assume either a de movo
initiation of g# from another source, or its persistencg at a very low level.
Induced reversion would be simply the "&nfection" cf s€lackingYgs)with #. One
could then state that barrage results from the confrontation ofhyphae carrying
g and S respectively.

Yours sincerely,

Joshua Lederbérg