类胡萝卜素是一大类结构相似的化合物，其裂解途径主要有羟化酶途径、双加氧酶裂解途径和氧化酶途径，能够形成一些激素和信号分子，从而调控植物发育。类胡萝卜素经羟化酶途径最终可转化成脱落酸，经氧化酶途径最终可转化成维生素A；而在裂解双加氧酶（Carotenoidcleavagedioxygenases,CCDs）催化下，类胡萝卜素氧化成脱辅基类胡萝卜素。最近，科研人员研究了水稻中的CCD家族成员，并发现其可以生成一种新的类胡萝卜素裂解代谢物，从而能够调控水稻生长和独脚金内酯的生物合成，提高水稻产量。
研究人员首先发现一种CCD蛋白（命名为ZAS）能够在体外生成一种新的类胡萝卜素裂解代谢物zaxinone，将体内的ZAS基因敲除后，水稻中zaxinone含量降低，发育迟缓，独脚金内酯的含量提高。独脚金内酯是一种影响植株株型，促进菌根生成和根部寄生杂草（如独脚金）生长的重要激素。外施zaxinone能够恢复突变体的表型，降低独脚金内酯含量并促进根部生长。因此，zaxinone对于促进水稻生长发育，抵御独脚金等寄生杂草对水稻的侵袭具有重要意义。
NatureCommunications,18February
Theapocarotenoidmetabolitezaxinoneregulatesgrowthandstrigolactonebiosynthesisinrice
Author
JianYouWang,ImranHaider,MuhammadJamil……LuisaLanfranco,PaolaBonfanteSalimAl-Babili*
*:DivisionofBiologicalandEnvironmentalScienceandEngineering,theBioActivesLab,KingAbdullahUniversityofScienceandTechnology,SaudiArabia
Abstract
Carotenoidcleavagedioxygenases(CCDs)formhormonesandsignalingmolecules.HereweshowthatamemberofanoverlookedplantCCDsubfamilyfromrice,thatwenameZaxinoneSynthase(ZAS),canproducezaxinone,anovelapocarotenoidmetaboliteinvitro.Loss-of-functionmutants(zas)containlesszaxinone,exhibitretardedgrowthandshowedelevatedlevelsofstrigolactones(SLs),ahormonethatdeterminesplantarchitecture,mediatesmycorrhizationandfacilitatesinfestationbyrootparasiticweeds,suchasStrigaspp.Applicationofzaxinonecanrescuezasphenotypes,decreaseSLcontentandreleaseandpromoterootgrowthinwild-typeseedlings.Inconclusion,weshowthatzaxinoneisakeyregulatorofricedevelopmentandbioticinteractionsandhaspotentialforincreasingcropgrowthand
