单子叶植物中的幼苗出苗主要取决于中胚轴伸长，需要发育信号与环境刺激之间的协调。 Strigolactones（SLs）和karrikins是丁烯内酯化合物，可调节各种发育过程。两者都能够在黑暗中负调节水稻中胚轴伸长率。
在这里，我们报告说，一个MAX2 1（OsSMAX1）的DWARF 14-LIKE（D14L）-DWARF 3（D3）-水稻 SUPPRESSOR的karrikin信号复合物在黑暗中调节水稻中胚轴伸长。
我们证明D14L识别karrikin信号并招募SCFD3泛素连接酶用于OsSMAX1的泛素化和降解，反映了SL诱导以及D14和D3依赖性的泛素化和D53降解。
OsSMAX1的过表达在黑暗中促进了胚轴伸长，而敲除OsSMAX1抑制了d14l和d3的伸长的胚轴表型，但对它们的分枝表型影响很小。 OsSMAX1位于细胞核中，并与TOPLESS相关蛋白（TPR）相互作用，调节下游基因的表达。
此外，我们表明GR24对映异构体GR245DS和GR24ent-5DS分别以D14和D14L依赖的方式特异性抑制中胚轴伸长并调节下游基因的表达。
图. KL信号通路反映了SL信号通路
我们的工作表明，karinkin和SL信号传导在调节下游基因表达和在黑暗中负面调节中胚轴伸长方面起着平行和累加的作用。
Abstract：
Seedling emergence in monocots depends mainly on mesocotyl elongation, requiring the coordination between developmental signals and environmental stimuli. Strigolactones (SLs) and karrikins are butenolide compounds that regulate various developmental processes; both are able to negatively regulate rice (Oryza sativa) mesocotyl elongation in the dark. Here, we report that a karrikin signaling complex, DWARF 14-LIKE (D14L)-DWARF 3 (D3)-Oryza sativa SUPPRESSOR OF MAX2 1 (OsSMAX1), regulates rice mesocotyl elongation in the dark. We demonstrate that D14L recognizes the karrikin signal and recruits the SCFD3 ubiquitin ligase for the ubiquitination and degradation of OsSMAX1, mirroring the SL-induced and D14and D3-dependent ubiquitination and degradation of D53. Overexpression of OsSMAX1 promoted mesocotyl elongation in the dark, whereas knockout of OsSMAX1 suppressed the elongated-mesocotyl phenotypes of d14l and d3 but had little effect on their shoot branching phenotype. OsSMAX1 localizes in nucleus and interacts with TOPLESS-RELATED PROTEINs (TPRs), regulating downstream gene expression. Moreover, we showed that the GR24 enantiomers GR245DS and GR24ent-5DS specifically inhibit mesocotyl elongation and regulate downstream gene expression in a D14and D14L-dependent manner, respectively. Our work revealed that karrikin and SL signaling play parallel and additive roles in modulating downstream genes expression and negatively regulating mesocotyl elongation in the dark.
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