  We report on the time variation of SiO maser emission from the symbiotic
stellar system V407 Cyg after the classical nova outburst on 2010 March 10.
Although both the SiO $J=1$--0 $v=1$ and 2 lines at 43.122 and 42.821 GHz were
found previously in the envelope of a mira in the binary system, only weak
emission of the $J=1$--0 $v=2$ line has continuously been detectable after the
nova outburst. The line profile exhibited a dramatic change several weeks after
the burst; the component on the higher-velocity side of the systemic velocity
disappeared two weeks after the burst, and a new persistent component appeared
on the lower-velocity side later. These observations indicate that the SiO
emitting regions are wiped out in a time scale of two weeks by the nova shock,
but a part of the masing region is quickly replenished by cool molecular gases
expelled by the mira pulsation.
