A Division in PIN-Mediated Auxin Patterning during Organ Initiation in Grasses
Figure 2
SoPIN1, PIN1a, PIN1b, and DR5 expression in the Brachypodium spikelet meristem.
(A) Organization of the Brachypodium spikelet meristem. Lemma primordia are colored red, floral meristems blue. Lemma primordia are labeled, I2, I1, P1, P2, P3 (see text). The spikelet meristem (SM), a single floral meristem (FM) and the P2 lemma (L) are labeled. Dashed box indicates area of detail images in Figure 3A–F. (B) Right, mature inflorescence with one lateral and one terminal spikelet, in brackets. Middle, a spikelet broken into the 2 bracts and 10 individual florets. Left, a single floret lemma, not to scale. (B Inset) Look-up-table scales for all fluorescence images. (C–H) Confocal maximum projections of PIN-Citrine and DR5-RFP expression in staged spikelet meristems. See supplemental Video S1. (C) SoPIN1 maximum projection including epidermal sections. (D) Internal SoPIN1 sections in same sample as (C), the spikelet meristem, floral meristems and lemma primordia are outlined in white for clarity. (E,G,H) Internal confocal sections of PIN1a and DR5 from a single plant expressing PIN1a and DR5. (E) PIN1a channel only, (G) DR5 only, and (H) DR5 and PIN1a. (F) Complete maximum projection showing PIN1b. Asterisks in (A), (C), and (D) show lemma midvein convergence points. Circles in (A) and (C) show lemma lateral vein convergence points on one side of meristem, see also Video S1. Ratios below each figure label indicate the number of times each phenomenon discussed in the text was observed out of the total imaged. Scale bars: 1 cm in (B), 25 µm in (C–H).