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There were gene clusters encoding photosynthesis components such as the psbB - psbH - petB - petD and the psbE - psbF clusters .
 psbB, psbH, petB, petD
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 psbB, psbH, petB, petD