Abstract:Summary
To reveal the mode of morphogenesis of flattened unifacial leaves, we analysed the cell division direction and distribution on the leaf blade of Juncus prismatocarpus.
Using the pulse–chase 5‐ethynyl‐2′‐deoxyuridine method, we quantified and mapped the cell division direction on the leaf blade of J. prismatocarpus and compared the distribution of thickening cell divisions with the expression pattern of DROOPING LEAF (DL), a key gene involved in leaf blade thickening.
Thickening cell divisions were th… Show more
“…Consistently, PRS is detected in the flattened leaf margin while not in the cylindrical leaf margin (Yamaguchi et al, 2010). Further analysis on cell division direction revealed that there is more thickening cell division on the adaxial domain than on the abaxial domain, which gives rise to flattened leaves like bifacial leaves (Yin and Tsukaya, 2019). Further investigation on unifacial leaf development may provide new insight into how leaves are flattened.…”
Leaves are the major organ for photosynthesis in most land plants, and leaf structure is optimized for the maximum capture of sunlight and gas exchange. Three polarity axes, the adaxial-abaxial axis, the proximal-distal axis, and the medial-lateral axis are established during leaf development to give rise to a flattened lamina with a large area for photosynthesis and blades that are extended on petioles for maximum sunlight. Adaxial cells are elongated, tightly packed cells with many chloroplasts, and their fate is specified by HD-ZIP III and related factors. Abaxial cells are rounder and loosely packed cells and their fate is established and maintained by YABBY family and KANADI family proteins. The activities of adaxial and abaxial regulators are coordinated by ASYMMETRIC LEAVES2 and auxin. Establishment of the proximodistal axis involves the BTB/POZ domain proteins BLADE-ON-PETIOLE1 and 2, whereas homeobox genes PRESSED FLOWER and WUSCHEL-RELATED HOMEOBOX1 mediate leaf development along the mediolateral axis. This review summarizes recent advances in leaf polarity establishment with a focus on the regulatory networks involved.
“…Consistently, PRS is detected in the flattened leaf margin while not in the cylindrical leaf margin (Yamaguchi et al, 2010). Further analysis on cell division direction revealed that there is more thickening cell division on the adaxial domain than on the abaxial domain, which gives rise to flattened leaves like bifacial leaves (Yin and Tsukaya, 2019). Further investigation on unifacial leaf development may provide new insight into how leaves are flattened.…”
Leaves are the major organ for photosynthesis in most land plants, and leaf structure is optimized for the maximum capture of sunlight and gas exchange. Three polarity axes, the adaxial-abaxial axis, the proximal-distal axis, and the medial-lateral axis are established during leaf development to give rise to a flattened lamina with a large area for photosynthesis and blades that are extended on petioles for maximum sunlight. Adaxial cells are elongated, tightly packed cells with many chloroplasts, and their fate is specified by HD-ZIP III and related factors. Abaxial cells are rounder and loosely packed cells and their fate is established and maintained by YABBY family and KANADI family proteins. The activities of adaxial and abaxial regulators are coordinated by ASYMMETRIC LEAVES2 and auxin. Establishment of the proximodistal axis involves the BTB/POZ domain proteins BLADE-ON-PETIOLE1 and 2, whereas homeobox genes PRESSED FLOWER and WUSCHEL-RELATED HOMEOBOX1 mediate leaf development along the mediolateral axis. This review summarizes recent advances in leaf polarity establishment with a focus on the regulatory networks involved.
“…Notably, wox3 triple mutant leaves with missing ligules retain adaxial–abaxial patterning at the BSB, indicating that disruption of ligule development is not due to the loss of adaxial–abaxial polarity (Extended Data Fig. 7b,c ) 29 . Fig.…”
Grass leaves develop from a ring of primordial initial cells within the periphery of the shoot apical meristem, a pool of organogenic stem cells that generates all of the organs of the plant shoot. At maturity, the grass leaf is a flattened, strap-like organ comprising a proximal supportive sheath surrounding the stem and a distal photosynthetic blade. The sheath and blade are partitioned by a hinge-like auricle and the ligule, a fringe of epidermally derived tissue that grows from the adaxial (top) leaf surface. Together, the ligule and auricle comprise morphological novelties that are specific to grass leaves. Understanding how the planar outgrowth of grass leaves and their adjoining ligules is genetically controlled can yield insight into their evolutionary origins. Here we use single-cell RNA-sequencing analyses to identify a ‘rim’ cell type present at the margins of maize leaf primordia. Cells in the leaf rim have a distinctive identity and share transcriptional signatures with proliferating ligule cells, suggesting that a shared developmental genetic programme patterns both leaves and ligules. Moreover, we show that rim function is regulated by genetically redundant Wuschel-like homeobox3 (WOX3) transcription factors. Higher-order mutations in maize Wox3 genes greatly reduce leaf width and disrupt ligule outgrowth and patterning. Together, these findings illustrate the generalizable use of a rim domain during planar growth of maize leaves and ligules, and suggest a parsimonious model for the homology of the grass ligule as a distal extension of the leaf sheath margin.
“…Cell pairs suitable for cell division orientation analysis are easily recognized in both Arabidopsis (Figure 3A) and J. prismatocarpus (Figure 3B) Tsukaya, 2016 and2019). Using these cell pairs, cell division angles can be quantified (Figure 4).…”
Section: Discussionmentioning
confidence: 99%
“…Using this method, we showed that cell division orientation is locally non-stochastic in leaf primordia of Arabidopsis thaliana (Arabidopsis), a model plant species for which leaf morphogenesis has been extensively studied (Yin and Tsukaya, 2016). Furthermore, we combined this method with conventional paraffin sectioning and analyzed cell division orientation in leaves with more complex structures such as those of Juncus prismatocarpus, a non-model plant species (Yin and Tsukaya, 2019).…”
In plants, the morphological diversity of leaves is largely determined by cell division, especially cell division orientation. Whereas cell division itself is easily monitored, the detection and quantification of cell division orientation are difficult. The few existing methods for detection and quantification of cell division orientation are either inefficient or laborious. Here, we describe a pulsechase strategy using a 5-ethynyl-2'-deoxyuridine (EdU) labeling assay. Plant tissues are first incubated with EdU for a short period (pulse), followed by a long incubation without EdU (chase). Using this method, the positions of daughter cells are easily detected and can be used to quantify cell division orientation.Our protocol is rapid and very efficient for quantitative analysis of cell division orientation, and can be applied to both model and non-model plant species.
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