Given the task definition and input, reply with output. In this task, you are given a sentence. You are expected to recognize the name of gene or protein. Although there might be several correct answers, you need to write one of them.

 Mutations in nifR1 ( ntrC ) and nifR4 ( rpoN , encoding sigma54 ) had no influence on xdh gene expression .

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
xdh gene