ZmbHLH121, a maize bHLH transcription factor inducing leaf senescence by accelerating ROS accumulation in maize (Zea mays L.)

Leaf senescence is the final stage of leaf development which is induced by many genetic and environmental factors. To reveal the role of transcription factors in leaf senescence, we studied the function of a bHLH transcription factor ZmbHLH121 in maize. The overexpression of ZmbHLH121 exhibited phenotypes with leaf senescence. Higher expression pattern of ZmbHLH121 was observed in the immature leaves through expression analysis at early vegetative developmental stages. Results of 3,3-diaminobenzidine (DAB), nitroblue tetrazolium chloride (NBT) histochemical analysis, quantitative measurement of reactive oxygen species (ROS), chlorophyll quantification and transcriptome analysis revealed that, ZmbHLH121 positively regulated leaf senescence by accelerating ROS production and chlorophyll breakdown in maize leaves. It is suggested that, ZmbHLH121 regulated leaf senescence might be due to the excess amount of ROS production and chlorophyll loss in leaves. This study provided useful clue about the mechanism of ZmbHLH121 mediated leaf senescence.