Parasitic plant infestations dramatically reduce the yield of many major food crops of sub-Saharan Africa and pose a serious threat to food security on that continent¹. The first committed step of a successful infestation is the germination of parasite seeds primarily in response to a group of related small-molecule hormones called strigolactones (SLs), which are emitted by host roots². Despite the important role of SLs, it is not clear how host-derived SLs germinate parasitic plants. In contrast, gibberellins (GA) acts as the dominant hormone for stimulation of germination in non-parasitic plant species by inhibiting a set of DELLA repressors³. Here, we show that expression of SL receptors from the parasitic plant Striga hermonthica in the presence of SLs circumvents the GA requirement for germination of Arabidopsis thaliana seed. Striga receptors co-opt and enhance signalling through the HYPOSENSITIVE TO LIGHT/KARRIKIN INSENSITIVE 2 (AtHTL/KAI2) pathway, which normally plays a rudimentary role in Arabidopsis seed germination^4,5. AtHTL/KAI2 negatively controls the SUPPRESSOR OF MAX2 1 (SMAX1) protein⁵, and loss of SMAX1 function allows germination in the presence of DELLA repressors. Our data suggest that ligand-dependent inactivation of SMAX1 in Striga and Arabidopsis can bypass GA-dependent germination in these species.

寄生植物的侵扰大大降低了撒哈拉以南非洲许多主要粮食作物的产量，并对该大陆的粮食安全构成了严重威胁¹。成功侵染的第一个重要步骤是寄生虫种子的发芽，主要是响应宿主根²释放的一组相关的小分子激素，称为strigolactones（SLs）。尽管SL发挥了重要作用，但尚不清楚宿主衍生的SL如何发芽寄生植物。相反，赤霉素（GA）通过抑制一组DELLA阻遏物^3，作为刺激非寄生植物物种萌发的主要激素。在这里，我们显示了寄生植物Striga hermonthica的SL受体表达在SL存在下，GA不能满足拟南芥种子发芽的GA要求。斯特里加受体协同选择并增强对光/ KARRIKIN敏感2（AtHTL / KAI2）的低信号传递途径，该途径通常在拟南芥种子萌发^4,5中起基本作用。AtHTL / KAI2负控制MAX2 1（SMAX1）蛋白^5的抑制子，SMAX1功能的丧失使存在DELLA阻遏物的发芽。我们的数据表明，Striga和拟南芥中SMAX1的依赖配体的失活可以绕开这些物种中GA的萌发。