To subtly indicate one's gender in a single sentence, you could say: "My mother always said I was her little princess." (For females) / "They call me the strong silent type." (For males). These sentences imply gender without explicitly stating it. There are many ways to express this depending on cultural context and personal style. Please let me know if you need more examples or specific variations.

To imply one's gender in the most subtle way:

"Use one sentence to subtly indicate your gender."

Source: http://www.foryn.cn

Note: The original Chinese question seems to request a very indirect or subtle sentence for indicating gender. A possible English example could be: "I tend to prefer my pronouns to match traditional conventions." This keeps the subtlety while hinting at gender through pronoun usage. If you'd like an alternative, let me know!