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Influence of clavata3-2 mutation on early flower development in Arabidopsis thaliana: quantitative analysis of changing geometry.

Szczesny T, Routier-Kierzkowska AL, Kwiatkowska D - J. Exp. Bot. (2008)

Bottom Line: In particular, the shape of the adaxial primordium boundary varies and seems to be related to the shape of the space available for the given primordium formation, suggesting that physical constraints play a significant role in primordium shape determination.Moreover, there is only one tunica layer in both the meristem and in the primordium until it becomes a bulge that is distinctly separated from the meristem.Starting from this stage, the anticlinal divisions predominate in subprotodermal cells, suggesting that the distribution of periclinal and anticlinal cell divisions in the early development of the flower primordium is not directly affected by the clv3-2 mutation.

View Article: PubMed Central - PubMed

Affiliation: Institute of Plant Biology, University of Wrocław, Kanonia 6/8, 50-328 Wrocław, Poland.

ABSTRACT
Early development of the flower primordium has been studied in Arabidopsis thaliana clavata3-2 (clv3-2) plants with the aid of sequential in vivo replicas and longitudinal microtome sections. Sequential replicas show that, although there is no regular phyllotaxis in the clv3-2 inflorescence shoot apex, the sites of new primordium formation are, to a large extent, predictable. The primordium always appears in a wedge-like region of the meristem periphery flanked by two older primordia. In general, stages of primordium development in clv3-2 are similar to the wild type, but quantitative geometry analysis shows that the clv3-2 primordium shape is affected even before the CLAVATA/WUSCHEL regulatory network would start to operate in the wild-type primordium. The shape of the youngest primordium in the mutant is more variable than in the wild type. In particular, the shape of the adaxial primordium boundary varies and seems to be related to the shape of the space available for the given primordium formation, suggesting that physical constraints play a significant role in primordium shape determination. The role of physical constraints is also manifested in that the shape of the primordium in the later stages, as well as the number and position of sepals, are adjusted to the available space. Longitudinal sections of clv3-2 apices show that the shape of surface cells of the meristem and young primordium is different from the wild type. Moreover, there is only one tunica layer in both the meristem and in the primordium until it becomes a bulge that is distinctly separated from the meristem. Starting from this stage, the anticlinal divisions predominate in subprotodermal cells, suggesting that the distribution of periclinal and anticlinal cell divisions in the early development of the flower primordium is not directly affected by the clv3-2 mutation.

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Flower primordium in which six sepals have been formed. Scanning electron micrographs (A, B), curvature plots (C, D), and side views of the reconstructed surface (E, F) show the portion of periphery of the clv3-2 inflorescence shoot apex No. 2, different from the portion shown in Fig. 4. Sepal primordia (S1–6) and the meristem (*) are labelled. The cellular pattern on the primordium periphery in the reconstruction (F) is missing due to the strong steepness of this primordium portion. Bars=20 μm. (This figure is available in colour at JXB online.)
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fig11: Flower primordium in which six sepals have been formed. Scanning electron micrographs (A, B), curvature plots (C, D), and side views of the reconstructed surface (E, F) show the portion of periphery of the clv3-2 inflorescence shoot apex No. 2, different from the portion shown in Fig. 4. Sepal primordia (S1–6) and the meristem (*) are labelled. The cellular pattern on the primordium periphery in the reconstruction (F) is missing due to the strong steepness of this primordium portion. Bars=20 μm. (This figure is available in colour at JXB online.)

Mentions: The bulge stage is followed by the formation of sepals (Figs 10, 11). In the clv3-2 flower primordium the sepal formation sites are difficult to predict. The number of sepals is variable and usually different from four (e.g. P1 in Fig. 11A has six sepals; five sepals will most likely be formed in the primordium in the upper part of Fig. 11D). The arrangement of sepals differs from the wild type, i.e. it is uncommon that there are two pairs of opposite sepals (for example, in the primordium in Fig. 10 a single sepal arises, while the flower primordium in Fig. 11 has three pairs of sepals) and the arrangement of sepals is usually not regular (the angular distances between adjacent sepals are different for example in Fig. 11B). Moreover, the width of sepal primordia (angular size) is often variable (e.g. compare sepal primordia of P2 in Fig. 12G or I). In some cases it is very difficult to define a boundary between the adjacent sepal primordia, as they seem to be fused (lateral sepals in Fig. 11B). In fact, in some cases a ring-like structure presumably formed via adjacent sepal fusion, surrounds the flower primordium dome (Fig. 12A–E). In all the cases the development of sepal primordia on the abaxial side of the flower primordium seems to be faster than on the adaxial side (compare abaxial and adaxial sepal of flower primordium in Fig. 11A, B), similar to the wild type flowers. The remaining dome of the flower primordium maintains positive Gaussian curvature (Figs 10C, D, 11C, D), and is not overtopped even by quite large sepal primordia (Fig. 11E, F). Also, even at this stage, the flower primordium remains overtopped by the SAM (Fig. 12I–K).


Influence of clavata3-2 mutation on early flower development in Arabidopsis thaliana: quantitative analysis of changing geometry.

Szczesny T, Routier-Kierzkowska AL, Kwiatkowska D - J. Exp. Bot. (2008)

Flower primordium in which six sepals have been formed. Scanning electron micrographs (A, B), curvature plots (C, D), and side views of the reconstructed surface (E, F) show the portion of periphery of the clv3-2 inflorescence shoot apex No. 2, different from the portion shown in Fig. 4. Sepal primordia (S1–6) and the meristem (*) are labelled. The cellular pattern on the primordium periphery in the reconstruction (F) is missing due to the strong steepness of this primordium portion. Bars=20 μm. (This figure is available in colour at JXB online.)
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2651453&req=5

fig11: Flower primordium in which six sepals have been formed. Scanning electron micrographs (A, B), curvature plots (C, D), and side views of the reconstructed surface (E, F) show the portion of periphery of the clv3-2 inflorescence shoot apex No. 2, different from the portion shown in Fig. 4. Sepal primordia (S1–6) and the meristem (*) are labelled. The cellular pattern on the primordium periphery in the reconstruction (F) is missing due to the strong steepness of this primordium portion. Bars=20 μm. (This figure is available in colour at JXB online.)
Mentions: The bulge stage is followed by the formation of sepals (Figs 10, 11). In the clv3-2 flower primordium the sepal formation sites are difficult to predict. The number of sepals is variable and usually different from four (e.g. P1 in Fig. 11A has six sepals; five sepals will most likely be formed in the primordium in the upper part of Fig. 11D). The arrangement of sepals differs from the wild type, i.e. it is uncommon that there are two pairs of opposite sepals (for example, in the primordium in Fig. 10 a single sepal arises, while the flower primordium in Fig. 11 has three pairs of sepals) and the arrangement of sepals is usually not regular (the angular distances between adjacent sepals are different for example in Fig. 11B). Moreover, the width of sepal primordia (angular size) is often variable (e.g. compare sepal primordia of P2 in Fig. 12G or I). In some cases it is very difficult to define a boundary between the adjacent sepal primordia, as they seem to be fused (lateral sepals in Fig. 11B). In fact, in some cases a ring-like structure presumably formed via adjacent sepal fusion, surrounds the flower primordium dome (Fig. 12A–E). In all the cases the development of sepal primordia on the abaxial side of the flower primordium seems to be faster than on the adaxial side (compare abaxial and adaxial sepal of flower primordium in Fig. 11A, B), similar to the wild type flowers. The remaining dome of the flower primordium maintains positive Gaussian curvature (Figs 10C, D, 11C, D), and is not overtopped even by quite large sepal primordia (Fig. 11E, F). Also, even at this stage, the flower primordium remains overtopped by the SAM (Fig. 12I–K).

Bottom Line: In particular, the shape of the adaxial primordium boundary varies and seems to be related to the shape of the space available for the given primordium formation, suggesting that physical constraints play a significant role in primordium shape determination.Moreover, there is only one tunica layer in both the meristem and in the primordium until it becomes a bulge that is distinctly separated from the meristem.Starting from this stage, the anticlinal divisions predominate in subprotodermal cells, suggesting that the distribution of periclinal and anticlinal cell divisions in the early development of the flower primordium is not directly affected by the clv3-2 mutation.

View Article: PubMed Central - PubMed

Affiliation: Institute of Plant Biology, University of Wrocław, Kanonia 6/8, 50-328 Wrocław, Poland.

ABSTRACT
Early development of the flower primordium has been studied in Arabidopsis thaliana clavata3-2 (clv3-2) plants with the aid of sequential in vivo replicas and longitudinal microtome sections. Sequential replicas show that, although there is no regular phyllotaxis in the clv3-2 inflorescence shoot apex, the sites of new primordium formation are, to a large extent, predictable. The primordium always appears in a wedge-like region of the meristem periphery flanked by two older primordia. In general, stages of primordium development in clv3-2 are similar to the wild type, but quantitative geometry analysis shows that the clv3-2 primordium shape is affected even before the CLAVATA/WUSCHEL regulatory network would start to operate in the wild-type primordium. The shape of the youngest primordium in the mutant is more variable than in the wild type. In particular, the shape of the adaxial primordium boundary varies and seems to be related to the shape of the space available for the given primordium formation, suggesting that physical constraints play a significant role in primordium shape determination. The role of physical constraints is also manifested in that the shape of the primordium in the later stages, as well as the number and position of sepals, are adjusted to the available space. Longitudinal sections of clv3-2 apices show that the shape of surface cells of the meristem and young primordium is different from the wild type. Moreover, there is only one tunica layer in both the meristem and in the primordium until it becomes a bulge that is distinctly separated from the meristem. Starting from this stage, the anticlinal divisions predominate in subprotodermal cells, suggesting that the distribution of periclinal and anticlinal cell divisions in the early development of the flower primordium is not directly affected by the clv3-2 mutation.

Show MeSH