SMAX1 interacts with DELLA protein to inhibit seed germination under weak light conditions via gibberellin biosynthesis in Arabidopsis
Peipei Xu,
Jinbo Hu,
Haiying Chen,
Weiming Cai
Affiliations
Peipei Xu
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; Corresponding author
Jinbo Hu
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
Haiying Chen
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
Weiming Cai
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; Corresponding author
Summary: 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 GA3 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.
