In this Letter, we used strain MT2124, the standard
let-60(
n1046gf)strain maintained in the Caenorhabditis Genetics Center, forodour-chemotaxis assays. However, we have found that this strain carries a side mutation(s) that profoundly impairs chemotaxis tothe odorant isoamyl alcohol, indicating that we need to re-evaluateour conclusion from the results shown in Fig. 1 that thelet-60
(n1046gf) mutant has a reduced efficiency of odorant chemotaxis.We outcrossed MT2124 to the wild-type N2 and obtained twolet-60
(n1046gf) strains, JN130 and JN131. We also outcrossed theMT4866 strain, the
let-60(
n2021lf) strain used in the study, andobtained the JN148 strain. All the outcrossed strains show reducedchemotaxis to the two odorants tested, isoamyl alcohol and diacetyl,at low odorant concentrations (T.H. and Y.I., unpublished results).The chemotaxis defects are comparable in extent to, or slightlyweaker than, the original MT4866
let-60(
n2021lf) strain. Ourconclusion that both inactivation and hyperactivation of LET-60Ras cause reduced chemotaxis therefore remains unchanged. However,the result shown in Fig. 1d, which suggested that
ksr-1(lf),
mek-2(lf) and
mpk-1(lf) suppress
let-60(
n1046gf), is no longer validbecause outcrossed
let-60(
n1046gf) strains do not show chemotaxisdefects at the odorant concentration used in Fig. 1d (1 1023dilution of isoamyl alcohol).