Dominant Lesion mutants on chromosome 2 and designation of Les18 and Les19
--M. G. Neuffer and Dan England

We have located 2 more EMS-induced dominant Les mutants to chromosome using the wx-marked reciprocal translocation method. The data for the locating crosses listed in Table 1 indicate that Les*-2441 is midway on 2S and Les*-2450 is proximal to wx1 T2-9d. Of the 31 known dominant Lesion mutants that we have worked with, 21 have been located to 7 chromosomes: 8 on chromosome 2, 4 on chromosome 1, 4 on chromosome 10, 2 on chromosome 3, and 1 each on chromosomes 6, 7 and 9. The high number on chromosome 2 suggests non-random distribution favoring that chromosome.

For comparison we have brought the available location data for all 8 mutants on chromosome 2 together in the table below. The data are not extensive nor highly accurate but nevertheless instructive about the possible positions of these mutants along the chromosome.

Les1, which is located on the genetic map at 58 between sk1 and wt1, has a recombination value of 14 ± 2% with wx1 T2-9b.

Les4 and Les*-1378 both show fairly close linkage (2 ±3% and 7 ±3%, respectively) to wx1 T2-9d which at .83 on the long arm (cytological map), and no linkage to wx1 T2-9b which is proximal on the short arm. This places these two mutants in the distal region of 2L.

Les10 shows moderate linkage with both wx1 T2-9b (25 ± 3% recombination) and wx1 T2-9d (33 ± 2% recombination), indicating that it is probably located between them in the proximal region of 2L.

Les11 shows moderate linkage (23 ± 4% recombination) with wx1 T2-9c and no linkage with wx1 T2-9d, indicating a location in the distal region of 2S.

Les15 shows close linkage (2 ± 1.5% recombination) with wx1 T2-9b suggesting location in the proximal region of 2S near Les1.

Les*-2441 shows good linkage (15 ±3 recombination) with wx1 T2-9c, moderate linkage (22 ± 4) with wx1 T2-9b, and no linkage with wx1 T2-9d, suggesting a distal location on 2S but not so far out as Les11, therefore we are designating this mutant Les18.

Les*-2450 shows moderate linkage with wx1 T2-9b (24 ±3% recombinant) and wx1 T2-9d (26 ± 5% recombination) but very loose linkage with wx1 T2-9c, suggesting a position between wx1 T2-9b and wx1 T2-9d in the mid-arm region of 2L. This is near the location of Les10, but since the two are much different in expression we are designating this mutant Les19.

With this information we can propose a tentative order along chromosome 2 as follows: Les11 distal 2S, Les18 distal 2S, Les1 mid-arm 2S, Les15 proximal 2S, Les10 and Les19 proximal-mid 2L, and Les4 and Les*-1378 distal 2L.

More precise data which may confirm or invalidate these positions will require linkage tests and/or interval mapping.

Table 1: Data from the cross of Wx Les/wx1 T2-9 on wx Normal for the wx translocations T2-9c (2S.49 bkpt), T2-9b (2S.18 bkpt) and T2-9d (2L.83 bkpt). The seed was separated for wx, plants and progeny were noted for Les phenotype. The mutant Les10-A607 arose spontaneously; the other Les mutants are EMS-induced.
 
Bkpt. Wx Les Wx + wx Les wx+ Recombination ±  Region
Les1-843
wx1 T2-9b 2S.18 171 30 19 126 .1416 ± .0187 2S (mid)
Les4-1375
wx1 T2-9b 2S.18 30 38 37 40 .4828 ± .0415
wx1 T2-9d 2L.83 75 14 6 74 .1183 ± .0248 2L (distal)
Les*-1378
wx1 T2-9b 2S.18 27 30 30 28 .4783 ± .0465
wx1 T2-9d 2L.83 47 1 5 39 .0652 ± .0257 2L (distal)
Les10-A607
wx1 T2-9b 2S.18 102 32 32 88 .2520 ± .0272
wx1 T2-9d 2L.83 157 74 71 134 .3326 ± .0226 2L (prox)
Les11-1438
wx1 T2-9c 2S.49 46 16 13 51 .2302 ± .0375
wx1 T2-9b 2S.18 65 75 61 85 .4755 ± .0295 2S (distal)
Les15-2007
wx1 T2-9b 2S.18 46 1 1 46 .0213 ± .0149 2S (prox)
Les18-2441
wx1 T2-9c 2S.49 62 3 18 58 .1489 ± .03
wx1 T2-9b 2S.18 47 17 9 46 .2185 ± .0379
wx1 T2-9d 2L.83 29 38 29 36 .4924 ± .0435 2S (distal)
Les19-2450
wx1 T2-9c 2S.49 45 30 35 46 .4167 ± .0395
wx1 T2-9b 2S.18 64 31 17 91 .2365 ± .0298
wx1 T2-9d 2L.83 25 9 9 26 .2609 ± .05 2L (prox)


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