Scientists Develop Transgenic Fish Species

New Delhi | Updated: Mar 25 2004, 05:30am hrs
India has developed experimental transgenics of rohu fish, zebra fish, cat fish and singhi fish. Genes, promoters and vectors of indigenous origin are now available for only two species namely rohu and singhi for engineering growth.

Transgenic rohu recently produced from indigenous construct at Madurai Kamaraj University has proved to be eight times larger than the control siblings. This transgenic rohu attains 46 to 49 gram body weight within 36 weeks of its birth. In India, research in transgenic fish was initiated in Madurai Kamaraj University (MKU), Centre for Cellular and Molecular Biology (CCMB), Hyderabad and National Matha College, Kollam with borrowed constructs from foreign scientists. The first Indian transgenic fish was generated in MKU in 1991 using borrowed constructs.

Taking the research further to promote the transgenic fish programme, the Indian Council of Agricultural Research (ICAR) plans to develop autotransgenesis in commercially important fish species with growth hormone gene.

ICAR plans also include production of pharmaceutical and other industrial products from piscine origin, development of transgenic native glow fish varieties, fish biosensors for monitoring aquatic pollution, isolation of genes, promoters and synthesis of effective gene constructs, researches in embryonic stem cells and in-vitro embryo production.

Indian scientists are concentrating on developing transgenic fish through autotransgenesis which involves just increasing the copies of growth hormone genes present in a fish as opposed to allotransgenesis which amounts to transfer of genes from different species.

The increase in growth homone genes leads to an increase in flesh content. Indian scientists feel that autotransgenesis is safer and less controversial.

However, the protocols are available for transformation of only a few fish species. Infrastructure and skilled manpower for transgenic fish production is highly limited. Biosafety testing procedures specific to aquatic animals are yet to be put in place.

But scientists like Dr TJ Pandian of the school of biological sciences in the Madurai Kamaraj University is confident that Indian scientists can excel their Asian counterparts in researches in transgenesis in fish species. He said that as an experimental model, various fish species have several advantages over mammalian model for transgenesis.

The generation time of most fish species is shorter and breeding frequency is relatively higher. A single female can produce several hundred or thousand eggs and thus provide a larger number of genetically identical eggs. Besides, the most important advantage is that the fertilisation is external and can be readily controlled by experimental manipulation, Mr Pandian said.

According to Mr Pandian, the limited availability of transgenes of piscine origin had been the major hurdle in production of transgenic fish. However, with advancements in molecular biology, more than 8,500 genes and cDNA sequences of piscine origin have been isolated, characterised and cloned in the world.

He added, Of these, 101 constitute commercially important genes belonging to the somatotropin family and only 44 of them are growth hormone sequences. In addition, less than a dozen of these sequences are inserted into appropriate vectors and are ready for gene transfer studies.