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Behavior of Leaf Meristems and Their Modification.

Ichihashi Y, Tsukaya H - Front Plant Sci (2015)

Bottom Line: Leaf organogenesis depends on activities of several distinct meristems that are established and spatiotemporally differentiated after the initiation of leaf primordia.Here, we review recent findings in the gene regulatory networks that orchestrate leaf meristem activities in a model plant Arabidopsis thaliana.We then discuss recent key studies investigating the natural variation in leaf morphology to understand how the gene regulatory networks modulate leaf meristems to yield a substantial diversity of leaf forms during the course of evolution.

View Article: PubMed Central - PubMed

Affiliation: RIKEN Center for Sustainable Resource Science Yokohama, Japan.

ABSTRACT
A major source of diversity in flowering plant form is the extensive variability of leaf shape and size. Leaf formation is initiated by recruitment of a handful of cells flanking the shoot apical meristem (SAM) to develop into a complex three-dimensional structure. Leaf organogenesis depends on activities of several distinct meristems that are established and spatiotemporally differentiated after the initiation of leaf primordia. Here, we review recent findings in the gene regulatory networks that orchestrate leaf meristem activities in a model plant Arabidopsis thaliana. We then discuss recent key studies investigating the natural variation in leaf morphology to understand how the gene regulatory networks modulate leaf meristems to yield a substantial diversity of leaf forms during the course of evolution.

No MeSH data available.


Related in: MedlinePlus

Leaf meristems of Arabidopsis thaliana. (A) Leaf developmental stages showing the proliferative region (red). This meristematic region localizes at the leaf blade/petiole junction and produces both leaf-blade and leaf-petiole cells in a bidirectional manner. The region maintains a constant size over a limited time period. (B) Left image: A leaf primordium at 7 days after sowing with cell lineages indicated by blue staining (sectors were induced at 4 days after sowing). The middle and right images indicate the spatial differentiation of leaf meristems. The plate meristem is marked by AN3 and WOX1 gene expression domains and the marginal meristem is marked by the SPT enhancer, PRS/WOX3, and the promoter of CYCD4;2.
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Figure 1: Leaf meristems of Arabidopsis thaliana. (A) Leaf developmental stages showing the proliferative region (red). This meristematic region localizes at the leaf blade/petiole junction and produces both leaf-blade and leaf-petiole cells in a bidirectional manner. The region maintains a constant size over a limited time period. (B) Left image: A leaf primordium at 7 days after sowing with cell lineages indicated by blue staining (sectors were induced at 4 days after sowing). The middle and right images indicate the spatial differentiation of leaf meristems. The plate meristem is marked by AN3 and WOX1 gene expression domains and the marginal meristem is marked by the SPT enhancer, PRS/WOX3, and the promoter of CYCD4;2.

Mentions: Plants have three major organs: leaves, stems, and roots. Stems and roots are directly derived from the shoot apical meristem (SAM) and the root apical meristem (RAM), respectively. The SAM and RAM maintain stem cells and exhibit indeterminate growth, which is an open-ended growth plan. On the other hand, leaves exhibit determinate growth, which is growth with a finite period of development. Meristems are defined, in a broad sense, as proliferating tissues regardless of presence of self-renewing stem cells, although the meristems have been controversial concept: Most molecular developmental biologists narrowly adopt a definition of meristems as proliferating tissues that maintain self-renewing stem cells, while meristematic tissues in leaves or stems are excluded by this definition at present because no stem cells have been observed in these tissues. (Esau, 1977; Tsukaya, 2014b). Notably WOX genes, which are key for sustaining stem cells both in SAM and RAM, are also important for the meristemactic activities in leaf primordia (Nardmann and Werr, 2013). The proliferative activity in leaf primordia is much stronger than that in the SAM, but cells that make a leaf come from restricted area of the primordium in angiosperms. Cell differentiation occurred subsequent to cell division makes the proliferative region in leaf separated spatially from SAM (Figure 1A). Therefore, leaf meristems producing leaf mesophyll cells as well as initial cells of stomata and veins are classified into intercalary meristems, that are meristematic tissues reside in a differentiating organ. Botanist Katherine Esau described in her textbook Plant Anatomy that a series of organogenesis steps in the leaf primordium depends on several distinct meristematic tissues including the plate meristem and the marginal meristem (Esau, 1977). The plate meristem consists of parallel layers of cells dividing anticlinally to play a major role in leaf growth. The marginal meristem, which is located at the edge of the leaf between the adaxial and abaxial surfaces, contributes to the establishment of tissue layers within the leaf.


Behavior of Leaf Meristems and Their Modification.

Ichihashi Y, Tsukaya H - Front Plant Sci (2015)

Leaf meristems of Arabidopsis thaliana. (A) Leaf developmental stages showing the proliferative region (red). This meristematic region localizes at the leaf blade/petiole junction and produces both leaf-blade and leaf-petiole cells in a bidirectional manner. The region maintains a constant size over a limited time period. (B) Left image: A leaf primordium at 7 days after sowing with cell lineages indicated by blue staining (sectors were induced at 4 days after sowing). The middle and right images indicate the spatial differentiation of leaf meristems. The plate meristem is marked by AN3 and WOX1 gene expression domains and the marginal meristem is marked by the SPT enhancer, PRS/WOX3, and the promoter of CYCD4;2.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4664833&req=5

Figure 1: Leaf meristems of Arabidopsis thaliana. (A) Leaf developmental stages showing the proliferative region (red). This meristematic region localizes at the leaf blade/petiole junction and produces both leaf-blade and leaf-petiole cells in a bidirectional manner. The region maintains a constant size over a limited time period. (B) Left image: A leaf primordium at 7 days after sowing with cell lineages indicated by blue staining (sectors were induced at 4 days after sowing). The middle and right images indicate the spatial differentiation of leaf meristems. The plate meristem is marked by AN3 and WOX1 gene expression domains and the marginal meristem is marked by the SPT enhancer, PRS/WOX3, and the promoter of CYCD4;2.
Mentions: Plants have three major organs: leaves, stems, and roots. Stems and roots are directly derived from the shoot apical meristem (SAM) and the root apical meristem (RAM), respectively. The SAM and RAM maintain stem cells and exhibit indeterminate growth, which is an open-ended growth plan. On the other hand, leaves exhibit determinate growth, which is growth with a finite period of development. Meristems are defined, in a broad sense, as proliferating tissues regardless of presence of self-renewing stem cells, although the meristems have been controversial concept: Most molecular developmental biologists narrowly adopt a definition of meristems as proliferating tissues that maintain self-renewing stem cells, while meristematic tissues in leaves or stems are excluded by this definition at present because no stem cells have been observed in these tissues. (Esau, 1977; Tsukaya, 2014b). Notably WOX genes, which are key for sustaining stem cells both in SAM and RAM, are also important for the meristemactic activities in leaf primordia (Nardmann and Werr, 2013). The proliferative activity in leaf primordia is much stronger than that in the SAM, but cells that make a leaf come from restricted area of the primordium in angiosperms. Cell differentiation occurred subsequent to cell division makes the proliferative region in leaf separated spatially from SAM (Figure 1A). Therefore, leaf meristems producing leaf mesophyll cells as well as initial cells of stomata and veins are classified into intercalary meristems, that are meristematic tissues reside in a differentiating organ. Botanist Katherine Esau described in her textbook Plant Anatomy that a series of organogenesis steps in the leaf primordium depends on several distinct meristematic tissues including the plate meristem and the marginal meristem (Esau, 1977). The plate meristem consists of parallel layers of cells dividing anticlinally to play a major role in leaf growth. The marginal meristem, which is located at the edge of the leaf between the adaxial and abaxial surfaces, contributes to the establishment of tissue layers within the leaf.

Bottom Line: Leaf organogenesis depends on activities of several distinct meristems that are established and spatiotemporally differentiated after the initiation of leaf primordia.Here, we review recent findings in the gene regulatory networks that orchestrate leaf meristem activities in a model plant Arabidopsis thaliana.We then discuss recent key studies investigating the natural variation in leaf morphology to understand how the gene regulatory networks modulate leaf meristems to yield a substantial diversity of leaf forms during the course of evolution.

View Article: PubMed Central - PubMed

Affiliation: RIKEN Center for Sustainable Resource Science Yokohama, Japan.

ABSTRACT
A major source of diversity in flowering plant form is the extensive variability of leaf shape and size. Leaf formation is initiated by recruitment of a handful of cells flanking the shoot apical meristem (SAM) to develop into a complex three-dimensional structure. Leaf organogenesis depends on activities of several distinct meristems that are established and spatiotemporally differentiated after the initiation of leaf primordia. Here, we review recent findings in the gene regulatory networks that orchestrate leaf meristem activities in a model plant Arabidopsis thaliana. We then discuss recent key studies investigating the natural variation in leaf morphology to understand how the gene regulatory networks modulate leaf meristems to yield a substantial diversity of leaf forms during the course of evolution.

No MeSH data available.


Related in: MedlinePlus