21514396
not annotated - annotated - LINNAEUS only
Altering sexual reproductive mode by interspecific exchange of MAT loci.
Sexual fungi can be self-sterile (heterothallic, requiring genetically distinct partners) or self-fertile (homothallic, no partner required). In most ascomycetes, a single mating type locus (MAT) controls the ability to reproduce sexually. In the genus Cochliobolus, all heterothallic species have either MAT1-1 or MAT1-2 (but never both) in different individuals whereas all homothallic species carry both MAT1-1 and MAT1-2 in the same nucleus of an individual. It has been demonstrated, previously, that a MAT gene from homothallic Cochliobolus luttrellii can confer self-mating ability on a mat-deleted strain of its heterothallic relative, Cochliobolus heterostrophus. In this reciprocal study, we expressed, separately, the heterothallic C. heterostrophus MAT1-1-1 and MAT1-2-1 genes in a mat-deleted homothallic C. luttrellii strain and asked if this converts homothallic C. luttrellii to heterothallism. We report that: (1) A C. luttrellii transgenic strain carrying C. heterostrophus MAT1-1-1 and a C. luttrellii transgenic strain carrying C. heterostrophus MAT1-2-1 can mate in a heterothallic manner and the fertility of the cross is similar to that of a wild type C. luttrellii self. Full tetrads are always found. (2) A C. luttrellii transgenic strain carrying C. heterostrophus MAT1-1-1 can mate with the parental wild type C. luttrellii MAT1-1;MAT1-2 strain, indicating the latter is able to outcross, a result which was expected but has not been demonstrated previously. (3) A C. luttrellii transgenic strain carrying C. heterostrophus MAT1-2-1 cannot mate with the parental wild type C. luttrellii MAT1-1;MAT1-2 strain, indicating outcrossing specificity. (4) Each transgenic C. luttrellii strain, carrying only a single C. heterostrophus MAT gene, is able to self, although all pseudothecia produced are smaller than those of wild type and fertility is low (about 4-15% of the number of wild type asci). These data support the argument that in Cochliobolus spp., the primary determinant of reproductive mode is MAT itself, and that a heterothallic strain can be made homothallic or a homothallic strain can be made heterothallic by exchange of MAT genes. The selfing ability of transgenic C. luttrellii strains also suggests that both MAT1-1-1 and MAT1-2-1 genes of C. heterostrophus carry equivalent transcription regulatory activities, each capable of promoting sexual development when alone, in a suitable genetic background.
Ann file
T1 Species 608 631 Cochliobolus luttrellii
N1 Reference T1 Taxonomy:90979
T2 Species 718 745 Cochliobolus heterostrophus
N2 Reference T2 Taxonomy:5016
T3 Species 817 834 C. heterostrophus
N3 Reference T3 Taxonomy:5016
T4 Species 892 905 C. luttrellii
N4 Reference T4 Taxonomy:90979
T5 Species 952 965 C. luttrellii
N5 Reference T5 Taxonomy:90979
T6 Species 1007 1020 C. luttrellii
N6 Reference T6 Taxonomy:90979
T7 Species 1048 1065 C. heterostrophus
N7 Reference T7 Taxonomy:5016
T8 Species 1081 1094 C. luttrellii
N8 Reference T8 Taxonomy:90979
T9 Species 1122 1139 C. heterostrophus
N9 Reference T9 Taxonomy:5016
T10 Species 1249 1262 C. luttrellii
N10 Reference T10 Taxonomy:90979
T11 Species 1306 1319 C. luttrellii
N11 Reference T11 Taxonomy:90979
T12 Species 1347 1364 C. heterostrophus
N12 Reference T12 Taxonomy:5016
T13 Species 1411 1424 C. luttrellii
N13 Reference T13 Taxonomy:90979
T14 Species 1566 1579 C. luttrellii
N14 Reference T14 Taxonomy:90979
T15 Species 1607 1624 C. heterostrophus
N15 Reference T15 Taxonomy:5016
T16 Species 1674 1687 C. luttrellii
N16 Reference T16 Taxonomy:90979
T17 Species 1766 1779 C. luttrellii
N17 Reference T17 Taxonomy:90979
T18 Species 1811 1828 C. heterostrophus
N18 Reference T18 Taxonomy:5016
T19 Species 2280 2293 C. luttrellii
N19 Reference T19 Taxonomy:90979
T20 Species 2357 2374 C. heterostrophus
N20 Reference T20 Taxonomy:5016