5166
A 73 bp fragment ( X1 region ) of the PRB - 1b promoter , located between positions - 213 and - 141 , was sufficient to confer ethylene responsiveness to the reporter gene .
 PRB - 1b promoter
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 PRB - 1b promoter