Kato Y, Oi T, Taniguchi M
Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan.
Plant Biol (Stuttg). 2023 Jun;25(4):563-570. doi: 10.1111/plb.13512. Epub 2023 Mar 10.
C plants supply concentrated CO to bundle sheath (BS) cells, improving photosynthetic efficiency by suppressing photorespiration. Mesophyll chloroplasts in C plants are redistributed toward the sides of the BS cells (aggregative movement) in response to environmental stresses under light. Although this chloroplast movement is common in C plants, the significance and mechanisms underlying the aggregative movement remain unknown. Under environmental stresses, such as drought and salt, CO uptake from the atmosphere is suppressed by closing stomata to prevent water loss. We hypothesized that CO limitation may induce the chloroplast aggregative movement. In this study, the mesophyll chloroplast arrangement in a leaf of finger millet, an NAD-malic enzyme type C plant, was examined under different CO concentrations and light conditions. CO limitation around the leaves promoted the aggregative movement, but the aggregative movement was not suppressed, even at the higher CO concentration than in the atmosphere, under high intensity blue light. In addition, mesophyll chloroplasts did not change their arrangement under darkness or red light. From these results, it can be concluded that CO limitation is not a direct inducer of the aggregative movement but would be a promoting factor of the movement under high intensity blue light.
C4植物将浓缩的二氧化碳输送到维管束鞘（BS）细胞，通过抑制光呼吸提高光合效率。在光照下，C4植物的叶肉叶绿体响应环境胁迫，向BS细胞一侧重新分布（聚集运动）。虽然这种叶绿体运动在C4植物中很常见，但聚集运动背后的意义和机制仍然未知。在干旱和盐等环境胁迫下，为防止水分流失，气孔关闭会抑制从大气中吸收二氧化碳。我们假设二氧化碳限制可能诱导叶绿体聚集运动。在本研究中，在不同二氧化碳浓度和光照条件下，研究了NAD - 苹果酸酶型C4植物黍叶中叶肉叶绿体的排列。叶片周围的二氧化碳限制促进了聚集运动，但在高强度蓝光下，即使二氧化碳浓度高于大气中的浓度，聚集运动也没有受到抑制。此外，在黑暗或红光下，叶肉叶绿体的排列没有变化。从这些结果可以得出结论，二氧化碳限制不是聚集运动的直接诱导因素，而是高强度蓝光下该运动的促进因素。
