CLONING AND SEQUENCING OF AN ALPHA-TUBULIN CDNA FROM ARTEMIA-FRANCISCANA - EVIDENCE FOR TRANSLATIONAL REGULATION OF ALPHA-TUBULIN SYNTHESIS

The brine shrimp, Artemia franciscana, exhibits a limited number of tu bulin isotypes which change little during early postgastrula growth. I n order to better understand the synthesis of alpha-tubulins during Ar temia development, a cDNA termed alpha AT1 was cloned and sequenced. A lignment analyses revealed that the polypeptide encoded by alpha AT1 i s similar to alpha-tubulins from other species. Hybridization of alpha AT1 to restriction-digested DNA on Southern blots produced a simple b anding pattern, indicating that Artemia have a small number of alpha-t ubulin genes. Probing of Northern blots demonstrated an abundant suppl y of alpha-tubulin mRNA in dormant cysts, emerging nauplii and instar I larvae. However, it was not until instar I larvae were produced that the amount of polysomal alpha-tubulin mRNA increased, suggesting that synthesis of the tubulin corresponding to alpha AT1 is translationall y controlled. This work provides one of the few examples where tubulin synthesis is thought to be translationally regulated. Moreover, when considered in the light of previous analyses, the findings imply that cell differentiation in postgastrula Artemia and the diversification o f microtubule function certain to accompany this process occur with li ttle or no change in alpha-tubulin composition. (C) 1998 Elsevier Scie nce B.V. All rights reserved.