Biologists in Australia and Japan have genetically engineered tobacco plants so that they destroy their own seeds. They say the same technique should work in citrus crops. Anna Koltunow of the division of horticulture of the CSIRO, Australia's national research agency in Adelaide, and Fumio Takaiwa of Japan's National Institute of Agrobiological Resources in Tsukuba, linked a gene that kills cells with a 'promoter' DNA sequence that switches on a gene active during seed formation. The researchers call their gene SDLS-2. The cell-killing component is found in a wide range of plants, and kills unwanted cells during plant development. The researchers are now inserting SDLS-2 into citrus plants, and are positive about the chances of success.