Laboratory of Photosynthesis and Environment, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, No. 300 Fenglin Road, Shanghai 200032, China; University of Chinese Academy of Sciences, Beijing 100039, China.
Laboratory of Photosynthesis and Environment, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, No. 300 Fenglin Road, Shanghai 200032, China; University of Chinese Academy of Sciences, Beijing 100039, China.
Cell Rep. 2023 Jul 25;42(7):112740. doi: 10.1016/j.celrep.2023.112740. Epub 2023 Jul 4.
Karrikins (KARs) were first identified as a class of small-molecule chemicals derived from smoke that promote seed germination. However, the implied mechanism is still not well understood. Here, we find that KAR signaling mutants have a lower germination percentage than that of wild type under weak light conditions, and KARs promote seed germination through transcriptional activation of gibberellin (GA) biosynthesis via SMAX1. SMAX1 interacts with the DELLA proteins REPRESSOR of ga1-3-LIKE 1 (RGL1) and RGL3. The interaction enhances the transcriptional activity of SMAX1 and inhibits GIBBERELLIN 3-oxidase 2 (GA3ox2) gene expression. The KAR signaling mutant seed germination defect under weak light is partially rescued by exogenous application of GA or by GA3ox2 overexpression, and the rgl1 rgl3 smax1 triple mutant exhibits higher germination rates under weak light than the smax1 mutant. Thus, we show a crosstalk between KAR and GA signaling pathways via a SMAX1-DELLA module in regulating seed germination in Arabidopsis.
卡尔基林（KAR）最初被鉴定为一类源自烟雾的小分子化学物质，能促进种子萌发。然而，其隐含的机制仍未被很好地理解。在这里，我们发现 KAR 信号突变体在弱光条件下的萌发率低于野生型，KAR 通过 SMAX1 对赤霉素（GA）生物合成的转录激活来促进种子萌发。SMAX1 与 DELLA 蛋白 REPRESSOR of ga1-3-LIKE 1（RGL1）和 RGL3 相互作用。这种相互作用增强了 SMAX1 的转录活性，并抑制了 GA3ox2 基因的表达。在弱光下，外源 GA 或 GA3ox2 过表达部分挽救了 KAR 信号突变体的种子萌发缺陷，rgl1 rgl3 smax1 三重突变体在弱光下的萌发率高于 smax1 突变体。因此，我们在拟南芥中通过 SMAX1-DELLA 模块显示了 KAR 和 GA 信号通路之间的串扰，从而调节种子萌发。
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