IDENTIFICATION OF A NOVEL BRUGIA-PAHANGI BETA-TUBULIN GENE (BETA-2) AND A 22-NUCLEOTIDE SPLICED LEADER SEQUENCE ON BETA-1-TUBULIN MESSENGER-RNA

We have examined the expression of beta-tubulin genes in the parasitic nematode, Brugia pahangi. A genomic library was constructed and screened by hybridization with a Haemonchus contortus beta-tubulin cDNA fragment which recognizes several B. pahangi beta-tubulin sequences, including sequences which correspond to the previously characterized beta-1-tubulin gene. The B. pahangi beta-2-tubulin gene was isolated by selecting clones which hybridize to the H. contortus beta-tubulin gene but which do not hybridize to the beta-1-tubulin gene. A partial sequence of the beta-2-tubulin gene confirms that it codes for a distinct beta-tubulin. Southern hybridization analyses show that the beta-2-tubulin sequence exists as a single copy gene within the B. pahangi genome. Expression of the beta-2-tubulin gene is developmentally regulated and the message is found predominantly in adult male worms, whereas the beta-1-tubulin gene is expressed in microfilariae and approximately equal levels of the transcript are found in male and female adult worms. During mRNA maturation the beta-1-tubulin mRNA of microfilariae and adult worms acquires a trans-spliced leader identical to the SL1 of Caenorhabditis elegans.