The Metabolite Pathway between Bundle Sheath and Mesophyll: Quantification of Plasmodesmata in Leaves of C3 and C4 Monocots
The Metabolite Pathway between Bundle Sheath and Mesophyll: Quantification of Plasmodesmata in Leaves of C3 and C4 Monocots
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DOI：
10.1105/tpc.16.00155
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发表时间：
2016-06-01
期刊：
影响因子：
11.6
通讯作者：
von Caemmerera, Susanne
中科院分区：
文献类型：
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作者：
Danila, Florence R.;Quick, William Paul;von Caemmerera, Susanne
C-4光合作用的特征是叶片叶肉细胞(M)和束鞘细胞(BS)之间的CO2浓缩机制。这通过相互连接胞间连丝(PD)在这些细胞之间产生了高代谢通量。要量化这些用于建模研究的共聚物通量，需要准确地定量PD，这已被证明很难使用透射电子显微镜。我们的新定量技术结合扫描电子显微镜和3D免疫定位在完整的叶片组织中比较了C-3(水稻和小麦)和C-4(玉米和狗尾草)单子叶物种叶片细胞界面上的Pd密度。扫描电子显微镜对Pd密度的量化表明，与C-3对应的物种相比，C-4物种每皮特菲尔德面积上的Pd数量大约是其两倍。用共聚焦显微镜三维免疫定位显示，在C-4物种中，每M-BS界面区域的Pitfield面积是C-4物种的5倍。因此，两个C-4物种每M-BS界面面积的PD高达9倍(S.viridis，9.3PD mm(-2)；玉米，7.5PD mm(-2)；水稻，1.0PD mm m(-2)；小麦，2.6PD mm m(-2))。利用这些解剖数据和测量的这些C-4物种的光合作用速率，我们现在已经计算了M-BS界面上每个PD的共生体C-4酸通量。这些定量数据对于将C-4光合作用的各个方面引入C-3作物所需的建模研究和基因发现策略是必不可少的。
C-4 photosynthesis is characterized by a CO2-concentrating mechanism between mesophyll (M) and bundle sheath (BS) cells of leaves. This generates high metabolic fluxes between these cells, through interconnecting plasmodesmata (PD). Quantification of these symplastic fluxes for modeling studies requires accurate quantification of PD, which has proven difficult using transmission electron microscopy. Our new quantitative technique combines scanning electron microscopy and 3D immunolocalization in intact leaf tissues to compare PD density on cell interfaces in leaves of C-3 (rice [Oryza sativa] and wheat [Triticum aestivum]) and C-4 (maize [Zea mays] and Setaria viridis) monocot species. Scanning electron microscopy quantification of PD density revealed that C-4 species had approximately twice the number of PD per pitfield area compared with their C-3 counterparts. 3D immunolocalization of callose at pitfields using confocal microscopy showed that pitfield area per M-BS interface area was 5 times greater in C-4 species. Thus, the two C-4 species had up to nine times more PD per M-BS interface area (S. viridis, 9.3 PD mu m(-2); maize, 7.5 PD mu m(-2); rice 1.0 PD mu m(-2); wheat, 2.6 PD mu m(-2)). Using these anatomical data and measured photosynthetic rates in these C-4 species, we have now calculated symplastic C-4 acid flux per PD across the M-BS interface. These quantitative data are essential for modeling studies and gene discovery strategies needed to introduce aspects of C-4 photosynthesis to C-3 crops.