Aubry Sylvain, Kneřová Jana, Hibberd Julian M
Department of Plant Sciences, Downing Street, University of Cambridge, Cambridge CB2 3EA, UK.
Department of Plant Sciences, Downing Street, University of Cambridge, Cambridge CB2 3EA, UK
J Exp Bot. 2014 Jul;65(13):3557-66. doi: 10.1093/jxb/ert350. Epub 2013 Nov 12.
There is currently significant interest in engineering the two-celled C4 photosynthesis pathway into crops such as rice in order to increase yield. This will require alterations to the biochemistry of photosynthesis in both mesophyll (M) and bundle-sheath (BS) cells, but also alterations to leaf anatomy. For example, the BS of C4 species is enlarged compared with that in C3 species. Because cell and nucleus size are often correlated, this study investigated whether nuclear endoreduplication is associated with increased differentiation and expansion of BS cells. Nuclei in the BS of C4 Cleome gynandra were tagged with green fluorescent protein. Confocal laser-scanning microscopy and flow cytometry of isolated nuclei were used to quantify size and DNA content in BS cells. The results showed a significant endoreduplication in BS cells of C. gynandra but not in additional C4 lineages from both the monocotyledonous and dicotyledenous plants. Furthermore, in the C3 species Arabidopsis thaliana, BS cells undergo endoreduplication. Due to this significant endoreduplication in the small BS cells of C3 A. thaliana, it was concluded that endoreduplication of BS nuclei in C4 plants is not linked to expansion and differentiation of BS cells, and therefore that alternative strategies to increase this compartment need to be sought in order to engineer C4 traits into C3 crops such as rice.
目前，人们对将两细胞C4光合作用途径引入水稻等作物以提高产量有着浓厚兴趣。这不仅需要改变叶肉（M）细胞和维管束鞘（BS）细胞中光合作用的生物化学过程，还需要改变叶片解剖结构。例如，与C3植物相比，C4植物的维管束鞘更大。由于细胞大小和细胞核大小通常相关，本研究调查了核内复制是否与维管束鞘细胞的分化和扩展增加有关。用绿色荧光蛋白标记C4植物白花菜维管束鞘中的细胞核。使用共聚焦激光扫描显微镜和分离细胞核的流式细胞术来量化维管束鞘细胞中的大小和DNA含量。结果表明，白花菜维管束鞘细胞中存在显著的核内复制，但单子叶和双子叶植物的其他C4谱系中不存在。此外，在C3植物拟南芥中，维管束鞘细胞也会发生核内复制。由于C3拟南芥小维管束鞘细胞中存在这种显著的核内复制，得出的结论是，C4植物维管束鞘细胞核的核内复制与维管束鞘细胞的扩展和分化无关，因此需要寻找其他策略来增加这个区域，以便将C4性状引入水稻等C3作物中。
