Extended Data Fig. 1: Expression pattern of RAK1/2/3/4.

GUS staining of RAKspro:GUS lines indicated that RAK1, RAK2, RAK3 and RAK4 were expressed in embryos at various developmental stages, including globular (a₁, e₁, i₁, m₁), transition (a₂, i₂), and heart stages (a₃ – a₄, e₂ – e₄, i₃ – i₄, m₂ – m₄). RAK1, RAK2, RAK3, RAK4 were expressed in 4-d-old seedlings (b, f, j, n), root apical meristems (c, g, k, o) and flowers of 40-d-old plants (d, h, l, p).GUS staining durations were 16-24 h for embryos, seedlings and flowers of RAK1pro:GUS plants, 1.5-4 h for embryos, seedlings and flowers of RAK2 pro:GUS and RAK4pro:GUS plants; 1.5 h for seedlings and flower organs, 24-36 h for embryos of RAK3pro:GUS plants. The experiments in a-p are repeated independently three times with similar results. Scale bars = 25 μm in (a₁) to (a₄); (e₁) to (e₄); (i₁) to (i₄); (m₁) to (m₄) and (c), (g), (k), (o); 1 mm in (b), (d), (f), (h), (j), (l), (n) and (p).