MAIN CONCLUSION The phloem-mobile protein SlCyp1 traffics to distant parts of the shoot to regulate its gravitropic response. In addition, SlCyp1 targets specific cells in the root to promote lateral root development. The tomato (Solanum lycopersicum) Cyclophilin 1 (SlCyp1) gene encodes a peptidyl-prolyl isomerase required for auxin response, lateral root development and gravitropic growth. The SlCyp1 protein is a phloem-mobile signal that moves from shoot to root to regulate lateral root development (Spiegelman et al., Plant J 83:853-863, 2015; J Exp Bot 68:953-964, 2017a). Here, we explored the mechanism of SlCyp1 movement by fusing it to the fluorescent protein mCherry. We found that, once trafficked to the root, SlCyp1 is unloaded from the phloem to the surrounding tissues, including the pericycle and lateral root primordia. Interestingly, SlCyp1 not only moves to the root system, but also to distant parts of the shoot. Grafting of the SlCyp1 mutant diageotropica (dgt) scions on VFN8 control rootstocks resulted in recovery of dgt shoot gravitropism, which was associated with the restoration of auxin-response capacity. Application of the cyclophilin inhibitor cyclosporine A suppressed gravitropic recovery, indicating that SlCyp1 must be active in the target tissue to affect the gravitropic response. These results provide new insights on the mechanism of SlCyp1 transport and functioning as a long-distance signal regulating shoot gravitropism.

中文翻译：

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亲环素 1 对番茄 (Solanum lycopersicum) 植物茎向地性的长距离调控

主要结论 韧皮部移动蛋白SlCyp1 运输到枝条的远处以调节其重力反应。此外，SlCyp1 靶向根中的特定细胞以促进侧根发育。番茄 (Solanum lycopersicum) Cyclophilin 1 (SlCyp1) 基因编码生长素反应、侧根发育和向地生长所需的肽基-脯氨酰异构酶。SlCyp1 蛋白是一种韧皮部移动信号，可从枝条移动到根部以调节侧根发育（Spiegelman 等人，Plant J 83:853-863, 2015；J Exp Bot 68:953-964, 2017a）。在这里，我们通过将其与荧光蛋白 mCherry 融合来探索 SlCyp1 运动的机制。我们发现，一旦被运输到根部，SlCyp1 就会从韧皮部卸载到周围组织，包括周轮和侧根原基。有趣的是，SlCyp1 不仅移动到根系，而且移动到枝条的较远部分。在 VFN8 对照砧木上嫁接 SlCyp1 突变体 diageotropica (dgt) 接穗导致 dgt 枝条向地性恢复，这与生长素反应能力的恢复有关。亲环素抑制剂环孢菌素A的应用抑制了向地恢复，表明SlCyp1必须在靶组织中具有活性才能影响向地反应。这些结果为 SlCyp1 转运的机制和作为调节茎向地性的长距离信号提供了新的见解。这与生长素反应能力的恢复有关。亲环素抑制剂环孢菌素A的应用抑制了向地恢复，表明SlCyp1必须在靶组织中具有活性才能影响向地反应。这些结果为 SlCyp1 转运的机制和作为调节茎向地性的长距离信号提供了新的见解。这与生长素反应能力的恢复有关。亲环素抑制剂环孢菌素A的应用抑制了向地恢复，表明SlCyp1必须在靶组织中具有活性才能影响向地反应。这些结果为 SlCyp1 转运的机制和作为调节茎向地性的长距离信号提供了新的见解。