Spiegelman Ziv, Omer Sumita, Mansfeld Ben N, Wolf Shmuel
The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Hebrew University of Jerusalem, The Robert H. Smith Faculty of Agriculture, Food and Environment, Rehovot 76100, Israel.
J Exp Bot. 2017 Feb 1;68(5):953-964. doi: 10.1093/jxb/erw487.
Tomato (Solanum lycopersicum) diageotropica (dgt) mutants, containing a single mutation in the Cyclophilin1 (SlCyp1) gene, are auxin-insensitive, exhibiting a pleiotropic phenotype including lack of geotropism, abnormal xylem structure, lack of lateral roots (LRs), and elevated shoot-to-root ratio. SlCyp1 is a putative peptidyl-prolyl isomerase that can traffic from shoot to root, where it induces changes in auxin response, LR formation, and xylem development, suggesting it has a role as a long-distance signaling molecule. Here, we explored the mechanism underlying SlCyp1 function in the phloem. Expression of SlCyp1 under a phloem-specific (AtSuc2) promoter in dgt plants partially restored the wild-type phenotype, including lateral root development, root branching, and xylem morphology. The observed developmental changes were associated with physiological alternations at the whole-plant level, including a reduction in shoot-to-root ratio, enhanced transpiration, and elevated photosynthetic rates. Conversely, phloem-specific expression of SlCyp1 active-site mutants did not restore the wild-type phenotype. Local inhibition of cyclophilin functioning in the target tissue reduced auxin sensitivity, suggesting that its enzymatic activity in the distant organ is required for its action as a long-distance signalling agent. The data presented suggest that SlCyp1 is a signal molecule trafficking from shoot to root where its activity is required for auxin-mediated lateral root development.
番茄（Solanum lycopersicum）的斜生（dgt）突变体在亲环蛋白1（SlCyp1）基因中存在单一突变，对生长素不敏感，表现出多效性表型，包括缺乏向地性、木质部结构异常、缺乏侧根以及茎根比升高。SlCyp1是一种假定的肽基脯氨酰异构酶，可从地上部运输到根部，在根部它会诱导生长素反应、侧根形成和木质部发育的变化，这表明它作为一种长距离信号分子发挥作用。在此，我们探究了SlCyp1在韧皮部中发挥功能的机制。在dgt植株中，在韧皮部特异性（AtSuc2）启动子控制下表达SlCyp1可部分恢复野生型表型，包括侧根发育、根分支和木质部形态。观察到的发育变化与整株水平的生理变化相关，包括茎根比降低、蒸腾作用增强和光合速率提高。相反，SlCyp1活性位点突变体的韧皮部特异性表达并未恢复野生型表型。在靶组织中局部抑制亲环蛋白的功能会降低生长素敏感性，这表明其在远处器官中的酶活性是其作为长距离信号传导剂发挥作用所必需的。所呈现的数据表明，SlCyp1是一种从地上部运输到根部的信号分子，其活性是生长素介导的侧根发育所必需的。
