Institute of Physics, Otto von Guericke University of Magdeburg, 39016, Magdeburg, Germany.
Department of Biophysics, Faculty of Biology, Moscow State University, Moscow, 119991, Russia.
Protoplasma. 2019 Nov;256(6):1737-1751. doi: 10.1007/s00709-019-01392-0. Epub 2019 Jul 31.
Characean internodal cells develop alternating patterns of acid and alkaline zones along their surface in order to facilitate uptake of carbon required for photosynthesis. In this study, we used a pH-indicating membrane dye, 4-heptadecylumbiliferone, to study the kinetics of alkaline band formation and decomposition. The differences in growth/decay kinetics suggested that growth occurred as an active, autocatalytic process, whereas decomposition was due to diffusion. We further investigated mutual interactions between internodal cells and found that their alignment parallel to each other induced matching of the pH banding patterns, which was mirrored by chloroplast activity. In non-aligned cells, the lowered photosynthetic activity was noted upon a rise of the external pH, suggesting that the matching of pH bands was due to a local elevation of membrane conductance by the high pH of the alkaline zones of neighboured cells. Finally, we show that the altered pH banding pattern caused the reorganization of the cortical cytoplasm. Complex plasma membrane elaborations (charasomes) were degraded via endocytosis, and mitochondria were moved away from the cortex when a previously acid region became alkaline and vice versa. Our data show that characean internodal cells react flexibly to environmental cues, including those originating from neighboured cells.
轮藻的节间细胞在其表面沿其长度方向形成酸区和碱区交替的模式，以促进光合作用所需的碳的吸收。在这项研究中，我们使用 pH 指示剂膜染料 4-十七烷基umbiliferone 来研究碱性带形成和分解的动力学。生长/衰减动力学的差异表明，生长是一种主动的、自催化的过程，而分解是由于扩散。我们进一步研究了节间细胞之间的相互作用，发现它们彼此平行排列诱导了 pH 带图案的匹配，这与叶绿体活性相呼应。在非对齐的细胞中，当外部 pH 值升高时，光合作用活性降低，这表明 pH 带的匹配是由于相邻细胞的碱性区的高 pH 值导致膜电导率局部升高所致。最后，我们表明，改变的 pH 带图案导致了皮质细胞质的重组。复杂的质膜结构（charasomes）通过内吞作用降解，当先前的酸性区域变为碱性区域时，线粒体从皮质迁移，反之亦然。我们的数据表明，轮藻的节间细胞对环境信号（包括来自相邻细胞的信号）反应灵活。
