In Episode IV: A New Hope when Commander Tagge is talking about the Rebellion gaining support in the senate Grand Moff Tarkin enters as says
The Imperial Senate will no longer be of any concern to us. I've just received word that the Emperor has dissolved the council permanently. The last remnants of the Old Republic have been swept away.
This got me thinking, considering that Palpatine would've had anyone oppose him killed and Jar Jar didn't seem all that enthusiastic about allowing the Grand Army of the Republic which became the groundwork for the Imperial Army what happened to Jar Jar after the Senate became "no more"?