Plant Physiology, Matthias Schleiden Institute for Genetics, Bioinformatics and Molecular Botany, Faculty of Biological Science, Friedrich Schiller University Jena, Dornburger Straße 159, 07743 Jena, Germany.
Department of Biochemistry, Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07745 Jena, Germany.
Int J Mol Sci. 2021 Jan 6;22(2):492. doi: 10.3390/ijms22020492.
Forisomes are giant fusiform protein complexes composed of sieve element occlusion (SEO) protein monomers, exclusively found in sieve elements (SEs) of legumes. Forisomes block the phloem mass flow by a Ca-induced conformational change (swelling and rounding). We studied the forisome reactivity in four different legume species-, , and . Depending on the species, we found direct relationships between SE diameter, forisome surface area and distance from the leaf tip, all indicative of a developmentally tuned regulation of SE diameter and forisome size. Heat-induced forisome dispersion occurred later with increasing distance from the stimulus site. and dispersion occurred faster for forisomes with a smaller surface area. Near the stimulus site, electro potential waves (EPWs)-overlapping action (APs), and variation potentials (VPs)-were linked with high full-dispersion rates of forisomes. Distance-associated reduction of forisome reactivity was assigned to the disintegration of EPWs into APs, VPs and system potentials (SPs). Overall, APs and SPs alone were unable to induce forisome dispersion and only VPs above a critical threshold were capable of inducing forisome reactions.
类蛋白体是由筛管阻塞蛋白单体组成的巨大梭形蛋白复合物，仅存在于豆科植物的筛管中。类蛋白体通过 Ca 诱导的构象变化（膨胀和变圆）来阻止韧皮部物质流。我们研究了四种不同豆科植物中的类蛋白体反应性，分别为 、 、 、 。根据物种的不同，我们发现 SE 直径、类蛋白体表面积和距叶尖的距离之间存在直接关系，这表明 SE 直径和类蛋白体大小的发育调节。距刺激部位越远，热诱导的类蛋白体分散发生得越晚。表面积较小的类蛋白体分散速度更快。在刺激部位附近，电势能波（EPWs）重叠动作电位（APs）和变化电位（VPs）与类蛋白体的高全分散率相关。与距离相关的类蛋白体反应性降低归因于 EPWs 分解为 APs、VPs 和系统电位（SPs）。总的来说，APs 和 SPs 本身不能诱导类蛋白体分散，只有超过临界阈值的 VPs 才能诱导类蛋白体反应。
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