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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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Side views of the reconstructed surfaces of sequential replicas of wild-type Arabidopsis (Columbia) apex, showing consecutive stages of flower primordium formation (A–E), and an exemplary median section of the wild-type apex (F). Each row represents side views of an individual shoot apex. The time at which replicas were taken is given below each reconstructed surface. (A) Initial lateral bulging of the meristem periphery leading to the shallow crease formation (arrow). (B) Early stages of bulging at the bottom of the shallow crease. (C) Later stage than shown in (B): note the rudimentary bract (x) that is a tiny lateral protrusion at the abaxial side of the primordium. (D) Bulge stage. Note that the initially apparent rudimentary bract (x) disappears. (E) Sepal formation stage. The flower primordium is always indicated by an arrow, the SAM by an asterisk. Bars=40 μm.
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fig15: Side views of the reconstructed surfaces of sequential replicas of wild-type Arabidopsis (Columbia) apex, showing consecutive stages of flower primordium formation (A–E), and an exemplary median section of the wild-type apex (F). Each row represents side views of an individual shoot apex. The time at which replicas were taken is given below each reconstructed surface. (A) Initial lateral bulging of the meristem periphery leading to the shallow crease formation (arrow). (B) Early stages of bulging at the bottom of the shallow crease. (C) Later stage than shown in (B): note the rudimentary bract (x) that is a tiny lateral protrusion at the abaxial side of the primordium. (D) Bulge stage. Note that the initially apparent rudimentary bract (x) disappears. (E) Sepal formation stage. The flower primordium is always indicated by an arrow, the SAM by an asterisk. Bars=40 μm.

Mentions: Longitudinal SAM sections (Fig. 13) show the distinct surface layer of protodermal cells where cell divisions are exclusively anticlinal. However, in subprotodermal cells not only anticlinal but also periclinal divisions occur both in the distal and in the proximal portions of the meristem (Fig. 13A–C), as well as at the putative sites of new flower primordium formation (Figs 13, 14A, B). Thus only one tunica layer is present in clv3-2 inflorescence SAM, unlike the wild-type inflorescence SAM where there are two tunica layers (Fig. 15F).


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)

Side views of the reconstructed surfaces of sequential replicas of wild-type Arabidopsis (Columbia) apex, showing consecutive stages of flower primordium formation (A–E), and an exemplary median section of the wild-type apex (F). Each row represents side views of an individual shoot apex. The time at which replicas were taken is given below each reconstructed surface. (A) Initial lateral bulging of the meristem periphery leading to the shallow crease formation (arrow). (B) Early stages of bulging at the bottom of the shallow crease. (C) Later stage than shown in (B): note the rudimentary bract (x) that is a tiny lateral protrusion at the abaxial side of the primordium. (D) Bulge stage. Note that the initially apparent rudimentary bract (x) disappears. (E) Sepal formation stage. The flower primordium is always indicated by an arrow, the SAM by an asterisk. Bars=40 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig15: Side views of the reconstructed surfaces of sequential replicas of wild-type Arabidopsis (Columbia) apex, showing consecutive stages of flower primordium formation (A–E), and an exemplary median section of the wild-type apex (F). Each row represents side views of an individual shoot apex. The time at which replicas were taken is given below each reconstructed surface. (A) Initial lateral bulging of the meristem periphery leading to the shallow crease formation (arrow). (B) Early stages of bulging at the bottom of the shallow crease. (C) Later stage than shown in (B): note the rudimentary bract (x) that is a tiny lateral protrusion at the abaxial side of the primordium. (D) Bulge stage. Note that the initially apparent rudimentary bract (x) disappears. (E) Sepal formation stage. The flower primordium is always indicated by an arrow, the SAM by an asterisk. Bars=40 μm.
Mentions: Longitudinal SAM sections (Fig. 13) show the distinct surface layer of protodermal cells where cell divisions are exclusively anticlinal. However, in subprotodermal cells not only anticlinal but also periclinal divisions occur both in the distal and in the proximal portions of the meristem (Fig. 13A–C), as well as at the putative sites of new flower primordium formation (Figs 13, 14A, B). Thus only one tunica layer is present in clv3-2 inflorescence SAM, unlike the wild-type inflorescence SAM where there are two tunica layers (Fig. 15F).

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
Related in: MedlinePlus