1620
S2F , a leaf - specific trans - acting factor , binds to a novel cis - acting element and differentially activates the RPL21 gene .
 GENE: S2F; GENE: RPL21 gene
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: GENE 
Text: {0} 
Answer:
 GENE: S2F; GENE: RPL21 gene