pole/zero locations for real and imaginary signal In Z-Transform, 

For a real signal,
 $x(n)$ =$x^*(n)$ . 
Taking Z-transform on both sides, 

$X(z)$=$X^*(z^*)$ ,  which gives certain pole/zero condition

similarly for a purely imaginary signal            ,

$x(n)$ =$-x^*(n)$ , if we take Z-Transform on both sides , $X(z)$=$-X^*(z^*)$ 

which gives similar pole/zero condition as that of real signal(poles and zeros are not effected by negative sign).

But  My professor says if the poles/zeros are symmetric with respect to real axis, then it is a real signal. But i am getting same condition for both real and imaginary signal.

Can anyone help me? (examples might be helpful)
I think there is a confusion between signals and systems here. A signal doesn't have any poles and zeros. Only systems have poles and zeros.

A system is a thing that turns one signal into another one. For example a loudspeaker turns a voltage signal into a sound signal. The voltage going in is a signal, the sound coming out is a signal, but the loudspeaker itself is a system. 

Linear Time Invariant Systems can be characterized by their transfer function or their impulse response. The transfer function in the Z domain can be written as a rationale function, which in turn can be characterized through poles and zeros. 

If the system has only a real valued input and only a real valued output, the impulse response must be real as well and that in turn will require the poles and zeros to be either real or be conjugate complex pairs.