How can i create similar lighting effect in Adobe Illustrator?
Marked with black border.
Another Example Here.
Using Gradients or a Gradient Mesh....
Transparency is used in the Gradient color stop, or the Gradient Mesh anchor points.
To promote the "light" aspect a bit more, you could also add a secondary shape behind the gradient mesh with a dark gradient for a sort of shadow in the "hole".
Or a light gradient to signify a stronger light....