(Adds deal details from paragraph 3) Top shareholder proxy firm...

(Adds deal details from paragraph 3)

Top shareholder proxy firm ISS has recommended investors vote in favour of Japan's Electric Power Development's (J-Power) 9513.T A$381 million ($257.56 million) buyout of Australia's Genex Power (GNX) , according to an ISS report.

An investor meeting to vote on the deal will be held in Sydney on Tuesday.

J-Power has offered 27.5 Australian cents per share for Genex, a renewable energy firm, in which it already owns 7.7%. The offer was a 48.5% premium to Genex's share price in early March before the J-Power bid was lobbed.

J-Power had originally offered 24 Australian cents, Genex said in March, before raising its offer to the current level that was backed by the buyout target's board.

In its report which was seen by Reuters, ISS said Genex investors should vote in favour of the bid which requires 75% shareholder support to proceed.

An independent expert's report from Grant Thornton earlier found that the J-Power offer was fair and reasonable.

J-Power, which is Japan's major power generator with coal-fired power plants and hydroelectric facilities, raised its 2030 emission reduction target last year by 1.3 million tons from 2013 levels.

The Japanese firm is a joint owner and developer of Genex's Kidston wind project and Bulli Creek clean energy project, which are both in the Australian state of Queensland. ($1 = 1.4793 Australian dollars)