27884
Here , we used next generation sequencing of the ovine PT transcriptome at melatonin onset , and identified Npas4 as a rapidly induced bHLH - PAS domain transcription factor .
 Chemical: melatonin
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: melatonin