whose responsibilty to sibmit form109?

It is a responsibility of both.

Responsibility from Student point of View:

A student cannot get other registration untill he submits 109. In this way it becomes responsibility and own interest of student to submit 109.

Responsibility from Employer point of view:

Articleship is reckoned under the former CA until he submits 109 of his article. In this way it becomes responsibility of CA to submit 109.