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Transgenic tobacco plants ( ppa - 1 ) constitutively expressing Escherichia coli pyrophosphatase behind the 35S CaMV promoter accumulate high levels of soluble sugars in their leaves [ 27 ] .
 ppa - 1, Escherichia coli pyrophosphatase, 35S CaMV promoter
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 ppa - 1, Escherichia coli pyrophosphatase, 35S CaMV promoter