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TUBULIN GENES EXPRESSED DURING EARLY DEVELOPMENT OF PATELLA VULGATA.

A.E. van Loon, M.E.M. Weijtens and A.J.J.M. Daemen, Department of Experimental Zoology, State University at Utrecht, Padualaan 8, 3584 CH Utrecht.

As a first step in studying the regulation of gene expression during the early development of the marine mollusc Patella vulgata, we have cloned cDNAs coding for tubulin. Tubulin was chosen because it is a major component of the cytoskeleton and present in high amounts in the embryo. Three different 8-tubulin cDNA clones were isolated and a large number of ~- tubulin cDNA clones. The DNA sequence of one ~-tubulin cDNA clone and of several s-tubulin cDNA clones has been determined. The fl- tubulin clone was nearly full length. The ~- tubulin clones were all 600 b.p. in length and corresponded to a part of the coding region in the C-terminal half of ~-tubulins of other species. Both the ~- and the ~- tubulin form a large gene family. In a Southern blot analysis more than 50 fragments could be detected with a probe corresponding to a coding region of either an ~- or #- tubulin cDNA clone. Both ~- and ~-tubulin mRNA is present in low amounts in the mature oocyte of Patella vulgata. During the first 4 hrs after fertilization the level does not rise. Between % and 8 hrs after fertilisation the amount increases i00-i000 times.

Abstract not received

49

Change in the Activity of Na+,K+-ATPase in Sea Urchin Embryos

1 1 2 L M1tsunaq_a , M__. Ha~ , K. Yamadayasumasu I' K. Akasaka 2", H. Shimada and I. _lq------ _-T . . . . . . . Dept. of Blol., Sch. of Educ., Waseda Univ., Tokyo, Japan. 2Zool. Inst., Fac. of Sci. , Hiroshima Univ. ¢ Hiroshima, Japan.

t Expression of Na ,K -ATPase in sea urchin embryos was investigated.

Na+,K+-ATPase activity in plasma membrane fraction scarcely altered before hatching and began to increase at the mesenchyme blastula stage. The activity reached to a maximum at the middle gastrula stage and thereafter decreased gradually. The increase was found to be dependent on embryo-wall cell fraction (ectodermal cells). Inhibition of transcription by actinomycin D before the hatching blastula stage did not affect the ATPase activity, while the inhibition between the hatching blastula and the mesenchyme blastula stages prevented the increase of the activity. cDNA clone, coding a sequence of ATP-binding site of Na+,K+-ATPase, hybridized to a about 4.5 Kb mRNA, which was maximally expressed at the mesenchyme blastula stage.

These results indicate that the increase of Na+,K+-ATPase activity at the gastrula stage is due to the transcription of the gene between the hatching blastula .~nd the mesenchyme blastula stage.

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PROTEIN SYNTHESIS IN MITOCHONDRIA OF ECHINODERM EMBRYOS K. Kawashima & T. Nakazawa* Dept. Biol., Toho Univ., Funabashi C., Japan

A transient increase in protein synthesis was observed in mitochon- drial fraction at the mesenchyme blastula stage of sea urchin and early gastrula stage of starfish embryos. In sea urchin embryos, the mitochondrial peptide elongation factor was essential for increasing the protein synthetic activity in mesenchyme blastula. On the other hand, in starfish embryos the ribo- some fraction containing initiation factor might be involved in the transient increase at early gastula stage through the interaction of mRNA, but the mitochondrial peptide elongation factor did not play a role in this increase. The molecular weights of mitochondrial proteins synthesized were estimated in embryos of both species. These findings are discussed in relation to the differ- entiation of embryos at the gastrula- tion stage.

$21