Altering arabinans increases Arabidopsis guard cell flexibility and stomatal opening.
Altering arabinans increases Arabidopsis guard cell flexibility and stomatal opening.
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DOI：
10.1016/j.cub.2022.05.042
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发表时间：
2022-07-25
期刊：
影响因子：
9.2
通讯作者：
Fleming, Andrew J.
中科院分区：
文献类型：
--
作者：
Carroll, Sarah;Amsbury, Sam;Durney, Clinton H.;Smith, Richard S.;Morris, Richard J.;Gray, Julie E.;Fleming, Andrew J.
气孔通过控制叶片气体交换来调节植物的水分利用和光合作用。它们通过可逆地打开两个相邻的保护细胞形成的孔来实现这一点，这种运动的极限最终由保护细胞壁和周围表皮的机械特性决定。大量证据表明，果胶壁聚合物的甲基化状态和细胞模式在设置保护细胞力学性能方面起着核心作用，该系统的破坏会导致气孔性能下降。在这里，我们提出的遗传和生化数据表明，阿拉伯壁菜调节保护细胞的灵活性，并可用于工程气孔提高性能。具体来说，我们发现与鼠李糖半乳糖酸I在保护细胞壁中的存在相关的短链线性阿拉伯蛋白表位是气孔完全打开所必需的。操纵导致长链阿拉伯蛋白表位在保护细胞壁上的新积累，导致最大孔径的增加。利用计算模型结合原子力显微镜，我们发现这种表型反映了壁基质刚度的降低，因此，在膨胀压力下，保护细胞的弯曲增加，产生更大、更圆的气孔。我们的研究结果为以下结论提供了理论和实验支持：果胶的阿拉伯糖侧链调节保护细胞壁的刚度，限制细胞的弯曲，从而限制气孔、气体交换和光合同化。气孔中的细胞壁具有明显的阿拉伯聚糖组成，增加特定阿拉伯聚糖的含量使细胞壁更加柔韧，细胞壁越柔韧的气孔开得越宽，在高CO2条件下，气孔越柔韧、越宽，可以增加碳的同化速率，气孔开放的程度是由保护细胞壁的力学特性决定的。Carroll等人表明，壁面的柔韧性是由阿拉伯聚糖组成的，通过操纵阿拉伯聚糖聚合物，可以在二氧化碳升高的情况下设计气孔，增加气孔的开度，从而增加碳的同化。
Stomata regulate plant water use and photosynthesis by controlling leaf gas exchange. They do this by reversibly opening the pore formed by two adjacent guard cells, with the limits of this movement ultimately set by the mechanical properties of the guard cell walls and surrounding epidermis. A body of evidence demonstrates that the methylation status and cellular patterning of pectin wall polymers play a core role in setting the guard cell mechanical properties, with disruption of the system leading to poorer stomatal performance. Here we present genetic and biochemical data showing that wall arabinans modulate guard cell flexibility and can be used to engineer stomata with improved performance. Specifically, we show that a short-chain linear arabinan epitope associated with the presence of rhamnogalacturonan I in the guard cell wall is required for full opening of the stomatal pore. Manipulations leading to the novel accumulation of longer-chain arabinan epitopes in guard cell walls led to an increase in the maximal pore aperture. Using computational modeling combined with atomic force microscopy, we show that this phenotype reflected a decrease in wall matrix stiffness and, consequently, increased flexing of the guard cells under turgor pressure, generating larger, rounder stomatal pores. Our results provide theoretical and experimental support for the conclusion that arabinan side chains of pectin modulate guard cell wall stiffness, setting the limits for cell flexing and, consequently, pore aperture, gas exchange, and photosynthetic assimilation. Cell walls in stomata have a distinct composition of arabinans Increasing the level of a specific arabinan makes the walls more flexible Stomata with more flexible walls can open wider Under high CO2, more flexible, wider stomata increase carbon assimilation rate The degree of stomatal opening is set by the mechanical properties of the guard cell walls. Carroll et al. show that wall flexibility is set by the arabinan composition, and that by manipulating arabinan polymers it is possible to engineer stomata with increased opening under elevated CO2, leading to increased carbon assimilation.
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