Stomata development of the anther is controlled by ICE1.

(A) GUS activity driven by ICE1 promoter is determined in the anther of flower stage 8 and 12. Strong GUS staining is shown in guard cells of stomata in the anther of flower stage 12 (indicated by red arrows). (B) Confocal images showing GFP-ICE1 accumulation (indicated by blue arrows) in the anther of flower stage 12. (C) Stomata numbers of anthers in flower stage 9–12. SE, n = 7–42 anthers. (D) Mode pattern of stomatal development in anthers. Diagram shows cell-state transitional steps within stomatal cell lineages. A subset of protodermal cells (white) assumes meristemoid mother cell (MMC) identity and executes an asymmetric entry division that creates meristemoids (M) (blue) and a sister cell, called stomatal-lineage ground cell (SLGC) (white). The meristemoids reiterate asymmetric amplifying division, but eventually differentiate into the guard mother cell (GMC) (green), which divides symmetrically once to form a stoma with differentiated guard cells (GCs) (red). (E) Scanning electron micrographs of the abaxial side of anthers at flower stage 8–14 in Col-0 (a-g). Anthers increase cell numbers from stage 8 to 9 (a-b). The stomatal lineage cells make their first appearance at about stage 9 (b). The number of stomatal lineage cells increases gradually during flower stage 9–12 (b-e). The majority of mature stomata are formed at about stage 12 (e). Inserts of anthers outline diagram show stomatal lineage cells with blue dots and mature stomata with red triangles. (F) Scanning electron micrographs of the abaxial side of anthers at flower stage 12 from Col-0, ice1-2 and c-ice1-2 plants. Cells colored in pink show distribution of mature stomata. Blue arrows indicate M and SLGC; green arrows indicate GMC; red arrows indicate GC. (G) Comparison of stomata numbers in Col-0, ice1-2 and c-ice1-2 plants at flower stage 12. SE, n = 30–42 anthers, *** p < 0.001).