Fluridone Induces Leaf Bleaching by Inhibiting Pigment Biosynthesis via Downregulated Transcription Levels of Pigment Biosynthetic Genes in Rice (Oryza Sativa L.).

Fluridone (FLU) is widely used as a herbicide and interferes with photosynthesis via induction of leaf bleaching. However, the mechanism of FLU-induced leaf bleaching remains elusive. In this study, the effects of FLU on the metabolism of leaf pigments, including chlorophyll and carotenoids, were investigated. Our results demonstrate that FLU induced rice leaf bleaching in a dose-dependent manner. Treatment with 5 µM FLU strongly induced leaf bleaching by decreasing pigment content, with carotenoids and chlorophyll decreased by 98 and 95%, respectively, in the second leaves of rice seedlings. Our results indicate that the transcription levels of leaf pigment biosynthetic and catabolic genes were significantly downregulated by 5 µM FLU treatment. These results suggest that FLU induces leaf bleaching by decreasing leaf pigment content via downregulation of the transcription levels of leaf pigment biosynthetic genes, and that the downregulation of transcription levels of leaf pigment catabolic genes is a result of feedback inhibition mediated by FLU-decreased leaf pigment content. In addition, to test whether FLU-induced leaf bleaching is due to FLU-induced abscisic acid (ABA) deficiency, the effect of FLU treatment on endogenous ABA content and the recovery effect of ABA on FLU-induced leaf bleaching were investigated. Application of FLU significantly decreased endogenous ABA content, but FLU-induced leaf bleaching was not rescued by ABA application, thus FLU-induced leaf bleaching is not due to FLU-induced ABA deficiency. [ABSTRACT FROM AUTHOR]