RESUMO
Karrikins (KAR) are a class of signal compounds, discovered in wildfire smoke, which affect seed germination. Currently, numerous studies have focused on the model plant Arabidopsis in the KAR research field, rather than on crops. Thus the regulatory mechanisms underlying KAR regulation of crop seed germination are largely unknown. Here, we report that KAR delayed soybean seed germination through enhancing abscisic acid (ABA) biosynthesis, while impairing gibberellin (GA) biogenesis. Interestingly, KAR only retarded soybean seed germination under shaded conditions, rather than under dark and white light conditions, which differs from in Arabidopsis. Phytohormone quantification showed that KAR enhanced ABA biogenesis while impairing GA biosynthesis during the seed imbibition process, and subsequently, the ratio of active GA4 to ABA was significantly reduced. Further qRT-PCR analysis showed that the transcription pattern of genes involved in ABA and GA metabolic pathways are consistent with the hormonal measurements. Finally, fluridone, an ABA biogenesis inhibitor, remarkably rescued the delayed-germination phenotype of KAR-treatment; and paclobutrazol, a GA biosynthesis inhibitor, inhibited soybean seed germination. Taken together, these evidences suggest that KAR inhibit soybean seed germination by mediating the ratio between GA and ABA biogenesis.
Assuntos
Ácido Abscísico/biossíntese , Furanos/farmacologia , Germinação/efeitos dos fármacos , Giberelinas/biossíntese , Glycine max/efeitos dos fármacos , Proteínas de Plantas/genética , Piranos/farmacologia , Sementes/efeitos dos fármacos , Ácido Abscísico/agonistas , Ácido Abscísico/antagonistas & inibidores , Regulação da Expressão Gênica de Plantas , Germinação/genética , Germinação/efeitos da radiação , Giberelinas/agonistas , Giberelinas/antagonistas & inibidores , Luz , Reguladores de Crescimento de Plantas/agonistas , Reguladores de Crescimento de Plantas/antagonistas & inibidores , Reguladores de Crescimento de Plantas/biossíntese , Proteínas de Plantas/metabolismo , Piridonas/farmacologia , Sementes/genética , Sementes/crescimento & desenvolvimento , Sementes/efeitos da radiação , Transdução de Sinais , Glycine max/genética , Glycine max/crescimento & desenvolvimento , Glycine max/efeitos da radiação , Transcrição Gênica , Triazóis/farmacologiaRESUMO
We identified a recessive, brassinolide-insensitive mutant caused by a deletion allele (bri1-201) of the brassinosteroid (BR) receptor BRI1. The bri1-201 mutant displayed altered expression levels of genes differentially regulated by gibberellin (GA). RNA-blot analysis revealed that BR and GA antagonistically regulate the accumulation of mRNAs of the GA-responsive GASA1 gene, as well as the GA-repressible GA5 gene. Expression studies with cycloheximide indicated that the antagonistic effects of GA and BR on GA5 require de novo protein synthesis. Reporter transgene analyses and RNA-blot analysis showed that BR and GA modulate GA5 expression, at least in part, at the transcriptional level, and that the signals are independent and subtractive.