Practice question

Organizing center in shoot apical meristem is small group of cells at base of central zone directly beneath totipotent stem cells functioning as niche organizer analogous to animal stem cell niches. It uniquely expresses WUSCHEL transcription factor whose protein migrates via plasmodesmata to overlying central zone conferring stem cell identity and activating CLV3 peptide expression. WUS expression is positively regulated by cytokinin via ARR, HAM GRAS factors, and low auxin, and negatively by CLV signaling through feedback loop. Thus organizing center serves as signaling source orchestrating meristem homeostasis and size maintenance.