Cytokinins Are Abundant and Widespread among Insect Species
Cytokinins Are Abundant and Widespread among Insect Species
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DOI：
10.3390/plants9020208
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发表时间：
2020-02-01
期刊：
影响因子：
4.5
通讯作者：
Connor, Edward F.
中科院分区：
文献类型：
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作者：
Andreas, Peter;Kisiala, Anna;Connor, Edward F.
细胞分裂素（CK）是一类长期以来被认为是植物生长调节剂的化合物。有趣的是，一些种类的植物病原细菌和真菌已被证明，并已被假设为胆囊诱导昆虫，产生CK并使用它们来操纵其宿主植物。我们使用高效液相色谱-电喷雾串联质谱（HPLC-MS/MS）检查17种植食性昆虫，包括虫瘿和非虫瘿诱导物种的浓度范围广泛的CKs从所有六个订单昆虫，包含已知的物种诱导虫瘿：缨翅目，半翅目，鳞翅目，鞘翅目，双翅目，和Hyattera。我们发现CKs在所有六个订单的昆虫，他们并不完全与胆囊诱导物种。我们检测到24种不同的CK分析物，其化学结构和生物活性各不相同。类异戊二烯前体核苷酸和核苷形式的反式玉米素（tZ）和异戊烯基腺嘌呤（iP）是最丰富和广泛的调查昆虫物种。值得注意的是，所观察到的CKs的浓度往往明显超过那些在植物中的报告，这表明昆虫合成CKs，而不是通过组织消耗，化合物螯合和生物积累从宿主植物中获得它们。这些研究结果支持昆虫来源的CKs作为手段的胆囊诱导昆虫操纵其宿主植物，以促进细胞增殖，并为胆囊和非胆囊诱导昆虫修改营养通量和植物防御在植食性。此外，广泛分布的CKs在植食性昆虫，包括非瘿诱导物种，表明昆虫传播的CKs可能参与操纵源-库机制的营养分配，以维持喂养的网站和改变植物的防御反应，而不仅仅是瘿诱导。由于没有任何证据表明昆虫中的从头CK生物合成途径中存在基因，我们推测tRNA-ipt途径负责CK的产生。然而，昆虫中CKs的异常高浓度，以及tZ和iP在其CK谱中占主导地位的趋势表明，tRNA-ipt途径在昆虫中的功能不同，并且比在植物中更有效。
Cytokinins (CKs) are a class of compounds that have long been thought to be exclusively plant growth regulators. Interestingly, some species of phytopathogenic bacteria and fungi have been shown to, and gall-inducing insects have been hypothesized to, produce CKs and use them to manipulate their host plants. We used high performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-MS/MS) to examine concentrations of a wide range of CKs in 17 species of phytophagous insects, including gall- and non-gall-inducing species from all six orders of Insecta that contain species known to induce galls: Thysanoptera, Hemiptera, Lepidoptera, Coleoptera, Diptera, and Hymenoptera. We found CKs in all six orders of insects, and they were not associated exclusively with gall-inducing species. We detected 24 different CK analytes, varying in their chemical structure and biological activity. Isoprenoid precursor nucleotide and riboside forms of trans-zeatin (tZ) and isopentenyladenine (iP) were most abundant and widespread across the surveyed insect species. Notably, the observed concentrations of CKs often markedly exceeded those reported in plants suggesting that insects are synthesizing CKs rather than obtaining them from the host plant via tissue consumption, compound sequestration, and bioaccumulation. These findings support insect-derived CKs as means for gall-inducing insects to manipulate their host plant to facilitate cell proliferation, and for both gall- and non-gall-inducing insects to modify nutrient flux and plant defenses during herbivory. Furthermore, wide distribution of CKs across phytophagous insects, including non-gall-inducing species, suggests that insect-borne CKs could be involved in manipulation of source-sink mechanisms of nutrient allocation to sustain the feeding site and altering plant defensive responses, rather than solely gall induction. Given the absence of any evidence for genes in the de novo CK biosynthesis pathway in insects, we postulate that the tRNA-ipt pathway is responsible for CK production. However, the unusually high concentrations of CKs in insects, and the tendency toward dominance of their CK profiles by tZ and iP suggest that the tRNA-ipt pathway functions differently and substantially more efficiently in insects than in plants.