This is the third ministry in the last 10 months since AIADMK won the assembly election in May 2016.
After Sasikala was sent to jail following her conviction in the disproportionate asset case by the Supreme Court, his loyalist Palanisami met the governor with the list of AIADMK MLAs supporting him.
Ending the 10-day impasse over government formation, Rao asked Palaniswami, the AIADMK Legislature Party Leader, to form his ministry at the earliest and given 15 days to seek a vote of confidence and prove majority in the assembly.
Palanisami is the third AIADMK leader to be sworn-in as Chief Minister in the last nine months. AIDMK supremo and Chief Minister J Jayalalithaa had powered the party to a rare successive term in office in the state in the May, 2016 Assembly Polls. She continued in the post through her grim 74-day battle for life.