NUCLEIC ACID SYNTHESIS DURING DIFFERENTIATION 

 OF BLASTOCLADIELLA EMERSONII 



James S. Lovett 



Department of Biological Sciences, Purdue University, 

 Lafayette, Indiana 



Because Dr. Cantino has already presented 

 an excellent summary of the life cycle of B. 

 emersonii (1), I can jump right into the material 

 I want to discuss without further introduction. 

 This will deal with the formation of zoospores, 

 which he skipped over very lightly, and their 

 germination, two phases in the life cycle that 

 are very close together. Before starting, how- 

 ever, I would like to mention that most of the 

 work on spore differentiation was done by a stu- 

 dent in my laboratory, Sister Mary Nadine 

 Murphy, now at Mundelein College, and the 

 electron micrographs I will show were prepared 

 in cooperation with Dr. A. E. Vatter, at the 

 University of Colorado Medical School, who 

 introduced me to the mysteries of electron 

 microscopy. 



We are interested in the formation of spores 

 and their germination for two reasons: one gen- 

 eral and one specific. In general, we feel that 

 the continuous transition from a relatively undif- 

 ferentiated plant with many nuclei to a large 

 number of highly differentiated spores and the 

 germination of these spores to give back tiny, 

 but nevertheless very similar, plants should 

 provide an excellent opportunity to study, and 

 perhaps even discover, some control mechan- 

 isms for the cellular regulation of differentia- 

 tion. Our specific reason is an interest in nuclei 

 acids and, particularly, the spore nuclear cap, 

 which is shown in the first figure (Fig. 1).* 



The zoospore is characterized by the large 

 "nuclear cap," a structure which has been known 

 for a long time. The spores in this photograph 



*Most of the figures presented here are schematic and 

 approximate to illustrate the material discussed. The com- 

 plete curves, micrographs, and experimental details will be 

 published elsewhere. 



were fixed and stained with the basic dye, tolui- 

 dine blue. In addition to the barely visible 

 flagellum, one can see the nucleus and a nucle- 

 olus. All of these structures can be seen better 

 in Fig. 2, which is an electron micrograph 



Fig. 1. 



Photomicrograph of a Blastocladiella zoospore, nc, 

 clear cap; n, nucleus; nu, nucleolus; fl, flagellum. 



Fig. 2. 



Electron micrograph of a section through a zoospore, 

 m, mitochondrion; v, vesicle; g, unidentified granule. 



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