Figure 2.

The Hd Phenotype Emerges Early in Development.

OPT of fixed time-course samples of wild-type ([A] and [D] to [I]) and Hd ([B] and [J] to [O]) Bowman barley inflorescences.

(A) to (C) Examples of inflorescence morphology at 0 and 340 h. Yellow boxes indicate the position of floret 5. The natural logarithm (ln) of floret 5 width (yellow line in the inset in [C]) was used to generate a combined log-linear growth curve (C) for the wild type (dark blue) and Hd (red) (n = 2 to 4 for each time point). The equation of the line of best fit (y = 0.0046x + 4.9305) (R² value of 0.8482) was used to stage all further experimental data. All times are hours since the initial morphology stage (0 h, illustrated in [A] and [B]).

(D) to (O) Lateral cross sections through the center of floret 5 ([D], [F], [H], [J], [L], and [N]) and images of the abaxial surface of the lemma ([E], [G], [I], [K], [M], and [O]) for different time points identified key morphology changes in the Hd lemma ([J] to [O]) versus the wild type ([D] to [I]). At 0 h ([D], [E], [J], and [K]), Hd and the wild type shared the same morphology: by 170 h ([F], [G], [L], and [M]), the ectopic meristem started to form on the adaxial surface of the Hd lemma (yellow box, white arrowhead), while the wild-type lemma elongated to form the awn ([F] to [I]). By 240 h, the wing outgrowths started to form in the margins below the ectopic flower in the Hd lemma ([N] and [O]). Zoomed-in images (yellow boxes) of the ectopic meristem and wings in Hd and the corresponding positions in the wild type are shown. Floral meristem (FM), lemma (Le), stamen (St), carpel (Ca), palea (Pa), wings (Wi), and awns (Aw). White dotted lines, shape of the lemma; white arrowheads, position of the ectopic meristem and wings.

Bars = 500 μm in (A) and (B) and 200 μm in (D) to (O).