Multiple Wnts act synergistically to induce Chk1/Grapes expression and mediate G2 arrest in tracheoblasts.

Larval tracheae of harbour progenitors of the adult tracheal system (tracheoblasts). Thoracic tracheoblasts are arrested in the G2 phase of the cell cycle in an ATR (mei-41)-Checkpoint Kinase1 (grapes, Chk1) dependent manner prior to mitotic re-entry. Here we investigate developmental regulation of Chk1 activation.