The constituencies, all reserved, include Ottapidaram, represented by PT founder-leader K Krishnasamy in the outgoing assembly, according to the poll-pact reached between the two parties.
DMK, leading the alliance, had yesterday allotted four seats to PT.
As per the agreement signed by DMK President M Karunanidhi and Krishnasamy, the other seats PT would contest are Vasudevanallur, Srivilliputhur and Krishnarayapuram.
Presently, Vasudevanallur and Krishnarayapuram are held by the ruling AIADMK while CPI represents Srivilliputhur.
An ally of AIADMK in the 2011 elections, PT later switched sides and supported DMK leader Kanimozhi's candidature in the 2013 Rajya Sabha elections.
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(REOPENS MES1)
DMK and another of its allies, Indian Union Muslim League, also identified the five constituencies the latter will contest.
(REOPENS MES2)
Another DMK ally, MMK , will contest from Ramanathapuram, Ambur, Thondamuthur, Ulunthoorpet and Nagapattinam.
The two parties arrived at a conclusion today over MMK's constituencies.
MMK, which had aligned with AIADMK for 2011 elections, represents Ramanathapuram and Ambur in the present assembly.