CHUP1 protein is involved in:
B fits best: Chloroplast positioning. Keep the Phototropin+All basics straight and Chloroplast positioning stands out as the precise answer. Avoid: A) Auxin transport; C) Stomatal closure; D) Photoperiodism. Light and flowering items often hinge on which photoreceptor or day-length rule is in play.
Ref: Best CSIR NET Plant Physiology books: Master Unit 6 with Taiz & Zeiger and Salisbury & Ross. Crack Part C experimental questions with top textbooks.