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. 2021 Oct 13;10:e70934. doi: 10.7554/eLife.70934

Figure 5. BAM1 expression is elevated in the flanks of the inflorescence meristem (IFM) and not detectable in the organizing centre (OC).

(A) Maximum intensity projection (MIP) of BAM1 under its endogenous promoter (BAM1:BAM1-GFP//bam1-3) at 5 weeks after germination (WAG). BAM1 expression is detected nearly throughout the entire inflorescence (IFM, flower meristem [FM], sepals) with weak expression in the central zone (CZ) of IFM and FMs (N = 15). (A’) MIP of the IFM from (A) without propidium iodide (PI) staining. (B) The layer 1 (L1) projection of the IFM shows ubiquitous expression of BAM1. (C) Longitudinal optical section through the IFM shows elevated BAM1 expression in the flanks (yellow arrows) and a lack of BAM1 expression in the OC. (C’) XZ section from (C) without PI staining. (P1–P6) BAM1 expression is found in all primordia cells. (D) MIP of BAM1 in a clv1-20 mutant (BAM1:BAM1-GFP//bam1-3;clv1-20). BAM1 expression is detected in most parts of the inflorescence, especially in the centre of the IFM and FMs (N = 9). (E) Cross-section (XY) of the IFM (from D) shows BAM1 expression in a clv1-20 mutant in the CZ (IFM and FMs) and the L1/L2. (F) Longitudinal optical section through the meristem (from D) shows BAM1 expression in the OC and the L1, while no BAM1 expression is detected in the peripheral zone (PZ) (yellow arrows). Dashed white and orange lines indicate longitudinal sections; dashed yellow lines in (C) and (F) mark the OC area, yellow lines (P1–P6) indicate the IFM region, white lines (P1–P6) mark the primordium and yellow arrows indicate high (C) or no (F) BAM1 expression in the PZ. Scale bars: 50 µm (A, D), 20 µm (B, C, E, F), 10 µm (P1–P6). P: primordium.

Figure 5.

Figure 5—figure supplement 1. The translational BAM1:BAM1-GFP reporter line rescues the shoot phenotype of the double mutant bam1-3;clv1-20.

Figure 5—figure supplement 1.

(A) Inflorescences (IFs) of bam1-3, clv1-20 at bam1-3;clv1-20 at 5 weeks after germination (WAG). The IF of clv1-20 mutants is enlarged compared to bam1-3 mutants. IFs of bam1-3;clv1-20 have a highly increased number of flowers and show an highly fasciated inflorescence meristem (IFM) compared to bam1-3 and clv1-20 mutants. (A’) IFs of bam1-3 mutants carrying the translational BAM1:BAM1-GFP show a wild-type-like IF and double mutants of bam1-3;clv1-20 plants carrying the BAM1:BAM1-GFP construct have IFs comparable to clv1-20 mutants. (B) The translational BAM1:BAM1-GFP construct rescues the fasciated meristem phenotype of bam1-3;clv1-20 plants. The upper panel shows no BAM1 expression (cyan channel) and a highly fasciated meristem (grey channel). The bottom panel shows BAM1 expression of the BAM1:BAM1-GFP construct in the IFM and primordia (cyan channel). Endogenous BAM1 expression rescues the fasciated meristem phenotype of bam1-3;clv1-20 (grey channel). Both meristems are from the same T2 line. Scale bars: 50 µm (B).
Figure 5—figure supplement 2. The translational BAM1 reporter line shows similar expression in three independent T1 lines.

Figure 5—figure supplement 2.

(A–C) Maximum intensity projections (MIPs) of three independent T1 lines of inflorescence meristems (IFMs) at 5 weeks after germination (WAG) expressing the translational reporter BAM1:BAM1-GFP//bam1-3 showing BAM1 expression in the IFM, flower meristems (FMs) and sepals. (A’–C’) XY sections of (A–C), respectively. XY sections show expression of BAM1 in all primordia and in the periphery of the IFM, but downregulated expression in the centre.
Figure 5—figure supplement 3. Expression of the translational BAM1 reporter (BAM1:BAM1-GFP) shifts from the PZ in bam1-3 mutants to the organizing centre (OC) and L1 in bam1-3;clv1-20 double mutants.

Figure 5—figure supplement 3.

(A–E) Maximum intensity projection (MIP) of five different inflorescence meristems (IFMs) at 5 weeks after germination (WAG) expressing the translational reporter BAM1:BAM1-GFP//bam1-3 showing BAM1 expression in the IFM and all primordia. (A’-–E’) XZ sections through the IFM of (A–E), respectively. XZ sections show expression of BAM1 in the peripheral zone (PZ), but downregulated expression in the OC. (F–J) MIP of five different IFMs at 5 WAG expressing the transcriptional reporter BAM1:BAM1-GFP//bam1-3;clv1-20. (F’–J’) XZ sections through the IFM of (F–J), respectively. XZ sections show that the expression of BAM1 shifted to the OC and L1 in a clv1-20 mutant background. Scale bars: 50 µm (A–J), 20 µm (A’–J’).
Figure 5—figure supplement 4. Quantification of expression pattern of the translational BAM1 reporter line in bam1-3 (N = 9) and bam1-3;clv1-20 (N = 9) mutants.

Figure 5—figure supplement 4.

(A) Optical XZ section through the centre of an inflorescence meristem (IFM) carrying the BAM1:BAM1-GFP//bam1-3 construct. BAM1 expression is elevated in the peripheral zone (PZ), downregulated in the organizing centre (OC) and weakly expressed in the primordia. (B) Longitudinal section through the IFM of a bam1-3;clv1-20 double mutant carrying the BAM1:BAM1-GFP construct. BAM1 expression is elevated in the L1, downregulated in the PZ and highly expressed in the OC. (C) Intensity plot profile of grey values through the centre of the XZ cross-sections of bam1-3 and bam1-3;clv1-20 mutants expressing the BAM1:BAM1-GFP reporter line (yellow dashed lines in A and B). For each genotype, nine meristems were analysed and the mean value (red and blue lines) with its standard deviation (error bars: grey) was plotted. Scale bars: 20 µm (A, B).
Figure 5—figure supplement 5. BAM1 and CLV1 are receptors for CLE40 and CLV3, respectively.

Figure 5—figure supplement 5.

(A, A’) Longitudinal and cross-sections of CLE40 (CLE40:Venus-H2B//Col-0) through the inflorescence meristem (IFM) show CLE40 expression in the peripheral zone (PZ) while no CLE40 expression is detected in the central zone (CZ) or the organizing centre (OC) (dashed yellow line). (B, B’) In longitudinal sections of BAM1 (BAM1:BAM1-GFP//bam1-3) through the IFM, elevated BAM1 expression in the PZ and young primordia can be detected, while low expression is found in the CZ and no expression is observed in the OC (dashed yellow line). (C, C’) Longitudinal and transversal section of CLV3 through the IFM (CLV3:NLS-3xmCherry//Col-0) shows CLV3 expression in the CZ (dashed yellow line). (D, D’) The native expression of CLV1 (CLV1:CLV1-GFP//Col-0) in an longitudinal and transversal section through the IFM is depicted in the OC (dashed yellow line) and in cells of the L1 and L2 close to emerging primordia. Scale bars: 20 µm (A–D’), yellow dashed lines indicate the OC (in A’, B’, D’) or the CZ (C’).
Figure 5—figure supplement 6. Expression patterns of CLE40 and BAM1 overlap in the inflorescence meristem (IFM).

Figure 5—figure supplement 6.

Longitudinal sections through an IFM and its developing primordia P1–P6 expressing either (A) CLE40 (CLE40:Venus-H2B) (N = 23) or (B) BAM1 (BAM1:BAM1-GFP) (N = 15). In the IFM, CLE40 and BAM1 expression patterns overlap in the peripheral zone (PZ), while both genes are lacking in the organizing centre (OC). No CLE40 expression is detected in young primordia in P1–P3. From P4 on a faint signal in central zone (CZ) of the primordia express CLE40. Its expression expands in P5 and can be found in almost all cells of P6. BAM1 is expressed ubiquitously in all primordia from P2 to P6. Yellow lines (P1–P6) indicate the IFM region, white lines (P1–P6) mark the primordium, Scale bar: 10 µm, P: primordium.