what is alternative splicing have to do with transgene silencing?

Answer 1

You may be aware that alternative splicing leads to the production of more than polypeptides from a gene.
One of these polyypeptides could go to the promoter site upstream of the transgene and bind tightly to disable RNA polymerase from binding or moving along. If this happens, the transgene would not be transcribed, which means it has been silenced. Or, imagine one of the polypeptides prodcued as a result of alternative splicing could do something to methylate the transgene to render is inactive, that is, silence it.