One of our major goals is to identify molecular components involved in thermotaxis to a preferred temperature. Toward this end, we have tried to isolate many thermotaxis-defective mutants using a unique method that utilized the interaction between daf-c and ttx mutations (see abstract by Okumura et al.). From these screens, new thermotaxis-defective mutants,
ttx-4(
nj1,
nj3) and
ttx-5(
nj2,
nj6), were isolated that show thermophilic and athermotactic phenotype, respectively. Both
ttx-4 and
ttx-5 mutants also show abnormal chemotactic responses to NaCl and odorants. To identify genes responsible for these abnormal behaviors, we characterized
ttx-4 and
ttx-5 mutations. By linkage analysis,
ttx-4 was found to map to the chromosome V . Three factor mappings suggested that
ttx-4 maps to the regions between
sma-1 and
vab-8. For identification of cosmid that rescued the
ttx-4 defects, we constructed several transgenic lines carrying single kinds of cosmids that map to the
ttx-4 region. The transformed lines transgenic with cosmid C38F2 were found to rescue
ttx-4 defects. C38F2 covers almost the same genomic region as F57F5. We PCR-amplified F57F5.4 region that encodes adducin, but the transformed lines transgenic with this PCR product did not rescue
ttx-4 defects. We then constructed a subclone containing F57F5.5 that encodes protein kinase C (
kin-13) and the 4kb region upstream of F57F5.5. The transformed lines trangenic with this subclone rescued
ttx-4 defects, suggesting that
ttx-4 gene encodes protein kinase C. At present, we are in the process of determining mutation sites of
ttx-4 alleles. By linkage analysis,
ttx-5(
nj2) was found to map to the chromosome III. Three factor mappings suggested that
ttx-5 (
nj2) maps to the regions between
unc-32 and
emb-9 and was found to be near the
lin-12 mutation. We are currently injecting several cosmids of the
ttx-5 region into
ttx-5 mutants in order to identify molecular nature of
ttx-5 gene.