signal-slot connection requires thread must be QThread?

[Bing]

Based on Qt document, "Qt provides thread support in the form of platform-independent threading classes, a thread-safe way of posting events, and signal-slot connections across threads.", I am wondering to make Qt signal-slot connection across threads work, do i have to make sure all the threads are created with QThread or Qt GUI thread?

For example, i have a Qt GUI thread, and i have a library running in another thread (Win32 thread). and in my GUI program, i override some virtual functions provided by the library which act as the callback function (based on publish/subscribe pattern). so the codes in the overridden virtual functions are actually executed in the Win32 thread. can i emit signal in the overridden function and let the slot in Qt GUI thread to connect with it to make the Async calling work?

Thanks