Recombination between mutants ofPhycomyces with abnormal phototropism

Abstract

Sexual crosses were studied between mutants of Phycomyces blakesleeanus with abnormal phototropism (phenotype mad). Recombination frequencies were determined among five genes madA to madE. No clear evidence was found for linkage between any of the genes. Inconsistent results in crosses involving madC are attributed to nonisogenicity between the particular strains used. One mad strain was discovered to be a double mutant. A new gene, tentatively designated madG, was segregated from a cross involving that strain.

Photocontrol of Fungal Development

“…Prior to a sexual analysis it was necessary to isolate mutants in similar genes in a (+) mating type. The first sexual crosses were reported by ESLAVA et al (1976). Whereas heterokaryon formation requires extreme dexterity, the sexual cycle is time-consuming.…”

“…They are affected only in phototropism and can be stimulated to bend by exceedingly high light intensities. By using sexual crosses it was possible to further ascertain that the seven complementation groups represent seven different genes, all unlinked (ESLAVA et al 1976. Using these techniques it was possible to construct a family of 21 double mad mutants and one triple mutant mad A, B, C .…”

Phycomyces blakesleeanus TRP1 gene: organization and functional complementation in Escherichia coli and Saccharomyces cerevisiae.

“…Upon illumination with blue light, the mycelium responds by increased synthesis of p-carotene and increased initiation of sporangiophores (5,11,13,17,18). Extensive genetic analyses have shown that at least eight complementation groups (madA through madH) are involved in the action network that controls the sensory responses of P. blakesleeanus (5,10,16,24). Recently, a transformation system for Phycomyces spp., based on the expression of the transposon Tn903-derived kanamycin resistance gene, has been established (26).…”

A New Genetic Linkage Map of the Zygomycete Fungus Phycomyces blakesleeanus

“…Whatever the mechanism(s) of recombination in the zygospore, individual genes could then be defined into complementation groups and their relative placement on chromosomes established through genetic linkage analysis. Over a two decade period this process led to the measurement of linkage distances based on segregation between these markers [20], [21], [22], [23], [24], [25], [26], including centromeres that were mapped with the equivalent of tetrad analysis [27], [28]. The first genetic map was reported in 1987 [28], and the updated map was published in 1996 [29].…”