  We study the response of the interacting electron gas in one dimension on the
local external potential. In the low frequency limit the power-law
singularities are essentially modifyed by backscattering effects which, in the
case of zero forward scattering, result in the universal critical exponent
depending only on the Luttinger-liquid interactions. The results obtained may
be used to describe singular responses of the 1D boson chains.
