Fine structure of genes controlling pathogenicity in flax rust, Melampsora lini

Abstract

SUMMARYThe fine-structure of four genes, A-F, A-P1, A-P2 and A-P3 in the flax rust organism, Melarnpsora lini, that control pathogenicity on the host, Linum usitatissimum, has been investigated by using a mass-screening procedure to search for rare recombinant progeny. Three presumptive recombinant individuals were recovered from amongst 3160 dikaryotic test-cross progeny and seven from a second test in which haploid basidiospores were screened for recombinants. From the pathogenicity phenotypes of the presumptive recombinants, and their frequency of occurrence, it is concluded that genes A-P, A-P1, A-P2 and A-P3 are sufficiently closely linked to belong to the same cistron. However, the possibility that they belong to separate, closely-linked cistrons can not be excluded: if they do belong to separate cistrons, then the data suggest that these are contiguous. A tentative gene order A-P A-P2 A-P1 A-P3 is proposed.

Studies of genes controlling specific host-parasite interactions in flax and its rust

“…Nevertheless, Shepherd and Mayo (1979) have demonstrated the compound nature of Flor's L6. Also there is suggestive evidence (Lawrence et al, 1979) that Victory A and Towner, assigned by FIor (1956) the single genes M4 and L8 respectively, may possess M ' and M4 and L8 and M4 respectively. The question therefore arises as to whether the use of a variety, such as Victory A, possessing more than one M gene, will thereby invalidate the analysis. In fact, it will proceed conventionally provided the two or more genes segregate as a single unit and maintain their original combined interaction with the strains of rust used.…”

“…Further progress is dependent on the availability of rust strains providing satisfactory differential specificity to the M genes, M2, M5 and M6. In addition, a strain that will clearly differentiate M1 and M4 is needed to resolve recent results suggesting M1 and M4 are both present in Victory A (Lawrence et al, 1979).…”

Melampsora Lini, Rust of Flax and Linseed

“…A L sA Lf A L -?la L sa L 6a L T) 9 mutants that have lost' only one of the avirulence specificities. However, in several studies of somatic variation in M. Uni involving strains heterozygous in coupling arrangement for genes in the A L sA L <A L i and Α Ρ Α Ρ Λ ρ2 Α Ρ^ groups, the only variants detected have been ones which have 'lost' all the avirulence specificities on a particular strand (Flor, 1956b(Flor, , 1958(Flor, , 1960(Flor, , 1964Lawrence et al, 1981b). Although the numerous variants recovered in these studies could be due to somatic recombination of some kind or, in one study where X-rays were used, to deletions of chromosome segments, these tests nevertheless were capable of detecting mutants with only a single change in specificity, and none were found.…”

“…The fine structure of the A P ,A P \,A P z,A P ?> group of specificities was further investigated by Lawrence et al (1981b) who used a mass-screening procedure to search for rare recombinant cultures. A strain heterozygous for all four specificities as follows, ApüpxapiüpJapApxApiAps (order arbitrary) was crossed to another strain homozygous recessive for all four factors to give test-cross progeny each consisting of a pustule of aeciospores.…”

Crystal structure of the Melampsora lini effector AvrP reveals insights into a possible nuclear function and recognition by the flax disease resistance protein P

“…The screening of an M. lini haustorium‐specific cDNA library revealed a haustorially expressed secreted protein gene cosegregating with a gene at the AvrP123 locus (Catanzariti et al ., ). So far, 10 AvrP123 alleles have been identified from rust isolates collected from flax species L. usitatissimum and Linum marginale , including AvrP and AvrP123 (Barrett et al ., ; Catanzariti et al ., ; Lawrence et al ., ). In flax, at least six rust resistance genes (P, P1–P5) occur at the complex P locus (Islam and Mayo, ).…”