Figure 1.

BAK1 and BKK1 regulate a light-dependent cell-death control pathway. (A) A representative Trypan blue stained wild-type cotyledon from a dark grown seedling on a ½ MS plate; (B) A representative Trypan blue stained bak1–4 bkk1-1 cotyledon from a dark grown seedling on a ½ MS plate; (C) A representative Trypan blue stained wild-type cotyledon from a long-day light-grown seedling on a ½ MS plate; (D) A representative Trypan blue stained bak1–4 bkk1-1 cotyledon from a long-day light-grown seedling on a ½ MS plate; (E) A hypothetical model of BAK1 and BKK1 in regulating both the BR signaling pathway to promote cell growth, and a novel light-dependent cell-death control pathway to prevent plants from unnecessary cell-death. Under a light condition, plants naturally produce unknown toxins (phototoxins), whose accumulation can lead to the cell-death. BAK1 and BKK1 likely mediate a signaling pathway to constantly check and limit the levels of these toxins.