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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Agrobacterium tumefaciens increases cytokinin production in plastids by modifying the biosynthetic pathway in the host plant
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Agrobacterium tumefaciens increases cytokinin production in plastids by modifying the biosynthetic pathway in the host plant

机译：根癌农杆菌通过修饰宿主植物的生物合成途径来增加质体中细胞分裂素的产生

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摘要

Agrobacterium tumefaciens infects plants and induces the formation of tumors called "crown galls" by integrating the transferred-DNA (T-DNA) region of the Ti-plasmid into the plant nuclear genome. Tumors are formed because the T-DNA encodes enzymes that modify the synthesis of two plant growth hormones, auxin and cytokinin (CK). Here, we show that a CK biosynthesis enzyme, Tmr, which is encoded by the Agrobacterium T-DNA region, is targeted to and functions in plastids of infected plant cells, despite having no typical plastid-targeting sequence. Evidence is provided that Tmr is an adenosine phosphate-isopentenyltransferase (IPT) that creates a new CK biosynthesis bypass by using 1-hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate (HMBDP) as a substrate. Unlike in the conventional CK biosynthesis pathway in plants, transzeatin-type CKs are produced directly without the requirement for P450 monooxygenase-mediated hydroxylation. Consistent with the plastid localization of Tmr, HMBDP is an intermediate in the methylerythritol phosphate pathway, a plastid-localized biosynthesis route for universal isoprenoid precursors. These results demonstrate that A. tumefaciens modifies CK biosynthesis by sending a key enzyme into plastids of the host plant to promote tumorigenesis.
机译：根癌农杆菌通过将Ti质粒的转移DNA（T-DNA）区域整合到植物核基因组中而感染植物并诱导称为“冠cro”的肿瘤的形成。因为T-DNA编码的酶会修饰两种植物生长激素（生长素和细胞分裂素（CK））的合成，所以会形成肿瘤。在这里，我们显示了由农杆菌T-DNA区域编码的CK生物合成酶Tmr靶向并在受感染植物细胞的质体中起作用，尽管没有典型的质体靶向序列。有证据表明，Tmr是磷酸腺苷-异戊烯基转移酶（IPT），它通过使用1-羟基-2-甲基-2-（E）-丁烯基4-二磷酸酯（HMBDP）作为底物来创建新的CK生物合成旁路。与植物中常规的CK生物合成途径不同，转基因型CKs直接产生而无需P450单加氧酶介导的羟基化作用。与Tmr的质体定位一致，HMBDP是甲基赤藓糖醇磷酸途径中的中间体，这是通用类异戊二烯前体的质体定位生物合成途径。这些结果表明，根癌农杆菌通过将关键酶发送到宿主植物的质体中来促进肿瘤发生而修饰CK的生物合成。

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