Carlactone is an endogenous biosynthetic precursor for strigolactones
Carlactone is an endogenous biosynthetic precursor for strigolactones
复制标题
木内酯是绞股蓝内酯的内源性生物合成前体
DOI：
10.1073/pnas.1314805111
复制
发表时间：
2014-01-28
影响因子：
11.1
通讯作者：
Yamaguchi, Shinjiro
中科院分区：
文献类型：
--
作者：
Seto, Yoshiya;Sado, Aika;Yamaguchi, Shinjiro
独igolactones （SLs）是一类萜类植物激素，具有调控植物茎枝分枝的作用，是植物共生和寄生的根源信号。SL有三环内酯（abc环）和甲基丁烯内酯（d环），它们通过烯醇醚桥连接。最近，通过体外对三种生物合成酶DWARF27、类胡萝卜素clev - age DIOXYGENASE 7 （CCD7）和CCD8的生化分析，发现了一种碳骨架部分类似于SLs的生物合成中间体——卡内酯（CL）。然而，从未从植物组织中鉴定出CL，也未在体内证实CL向SLs的转化。为了解决这些问题，我们化学合成了c -13标记的CL。我们发现，在CCD8中存在缺陷的矮子10突变体中，C-13标记的CL转化为(-)-[C-13]-2′-epi-5-脱氧己糖醇（(-)-2′-epi- 5ds）和[C-13]-orobanchol，这是水稻的内源SLs。此外，我们利用液相色谱-四极杆/飞行时间串联质谱技术成功鉴定了水稻和拟南芥中的内源CL。此外，我们确定了内源性CL的绝对立体化学结构为（11R）构型，与(-)-2′-epi- 5ds在相应位置的绝对立体化学结构相同。饲养实验表明，体内只有CL的(11R)-异构体转化为(-)-2′-epi- 5ds，而CL的(11S)-异构体不转化为(-)-2′-epi- 5ds。综上所述，我们的数据提供了确凿的证据，证明CL是内源性SL前体，在生物合成途径中被立体特异性识别。
Strigolactones (SLs) are a class of terpenoid plant hormones that regulate shoot branching as well as being known as root-derived signals for symbiosis and parasitism. SL has tricyclic-lactone (ABC-ring) and methyl butenolide (D-ring), and they are connected through an enol ether bridge. Recently, a putative biosynthetic intermediate called carlactone (CL), of which carbon skeleton is in part similar to those of SLs, was identified by biochemical analysis of three biosynthetic enzymes, DWARF27, CAROTENOID CLEAV-AGE DIOXYGENASE 7 (CCD7), and CCD8 in vitro. However, CL has never been identified from plant tissues, and the conversion of CL to SLs has not been proven in vivo. To address these questions, we chemically synthesized C-13-labeled CL. We show that C-13-labeled CL is converted to (-)-[C-13]-2'-epi-5-deoxystrigol ((-)-2'-epi-5DS) and [C-13]-orobanchol, endogenous SLs in rice, in the dwarf10 mutant, which is defective in CCD8. In addition, we successfully identified endogenous CL by using liquid chromatography-quadrupole/time-of-flight tandem mass spectrometry in rice and Arabidopsis. Furthermore, we determined the absolute stereochemistry of endogenous CL to be (11R)-configuration, which is the same as that of (-)-2'-epi-5DS at the corresponding position. Feeding experiments showed that only the (11R)-isomer of CL, but not the (11S)-isomer, was converted to (-)-2'-epi-5DS in vivo. Taken together, our data provide conclusive evidence that CL is an endogenous SL precursor that is stereospecifically recognized in the biosynthesis pathway.