LINKAGE OF MUTATIONS AFFECTING MINUS FLAGELLAR MEMBRANE AGGLUTINABILITY TO THE mt  - MATING-TYPE LOCUS OF CHLAMYDOMONAS

Abstract

Two independently isolated mutant strains, imp-10 and imp-12, were obtained by UV irradiation of wild-type mating-type minus (wt-). Each fails to agglutinate sexually with gametes of either mating type, but mating and zygote formation can be elicited by agglutinating either strain to wt+ gametes by means of anti-flagellar antiserum. Tetrad analysis of the resultant zygotes shows that both imp-10 and imp-12 are very closely linked to mt -, with no recombinants observed. Diploid strains constructed between imp-10 or imp-12 and wt+ gametes are wt-, that is, they agglutinate and fuse like normal minus cells. Tetrad analysis of triploids from imp-10 diploid x wt+ haploid crosses shows that only imp-10 and wt+ products are recovered. A model is proposed to account for these results.

HAP2-Mediated Gamete Fusion: Lessons From the World of Unicellular Eukaryotes

“…Aggregates eventually sort themselves into individual plus and minus pairs that then fuse. Ciliary adhesion is mediated by multi-pass transmembrane proteins (agglutinins) on plus and minus gametes named SAG1 and SAD1, respectively (Goodenough et al, 1978;Hwang et al, 1981;Ferris et al, 2005). Interactions between these proteins trigger protein kinase-and kinesin-2 dependent activation of a ciliary adenylyl cyclase, followed almost immediately by a near 20fold increase in intracellular levels of cAMP (Zhang et al, 1991;Saito et al, 1993;Pan and Snell, 2002;Wang et al, 2006;Snell and Goodenough, 2009).…”