ANAC087 transcription factor positively regulates age-dependent leaf senescence through modulating the expression of...

Leaf senescence is the final stage of leaf development and appropriate onset and progression of leaf senescence are critical for reproductive success and fitness. Although great progress has been made in identifying key genes regulating leaf senescence and elucidating the underlining mechanisms in the model plant Arabidopsis, there is still a gap to understanding the complex regulatory network. In this study, we discovered that Arabidopsis ANAC087 transcription factor (TF) positively modulated leaf senescence. Expression of ANAC087 was induced in senescing leaves and the encoded protein acted as a transcriptional activator. Both constitutive and inducible overexpression lines of ANAC087 showed earlier senescence than control plants, whereas T-DNA insertion mutation and dominant repression of the ANAC087 delayed senescence rate. A quantitative reverse transcription-polymerase chain reaction (qRT-PCR) profiling showed that the expression of an array of senescence-associated genes was upregulated in inducible ANAC087 overexpression plants including BFN1, NYE1, CEP1, RbohD, SAG13, SAG15, and VPEs, which are involved in programmed cell death (PCD), chlorophyll degradation and reactive oxygen species (ROS) accumulation. In addition, electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation-quantitative polymerase chain reaction (ChIP-qPCR) assays demonstrated that ANAC087 directly bound to the canonical NAC recognition sequence (NACRS) motif in promoters of its target genes. Moreover, mutation of two representative target genes, BFN1 or NYE1 alleviated the senescence rate of ANAC087-overexpression plants, suggesting their genetic regulatory relationship. Taken together, this study indicates that ANAC087 serves as an important regulator linking PCD, ROS, and chlorophyll degradation to leaf senescence.