BrJUB1, a NAC family transcription factor, regulates postharvest leaf senescence of Chinese flowering cabbage through the transcriptional activation of BrCCGs

Abstract

ABSTRACT Leaf yellowing caused by chlorophyll degradation directly reduces the commercial quality of post-harvest Chinese flowering cabbage. However, the mechanism of chlorophyll degradation in post-harvest Chinese flowering cabbage remains unclear. In this work, we identified a leaf senescence-responsive NAC family transcription factor, a homologue of JUB1 in Arabidopsis, termed BrJUB1 in post-harvest Chinese flowering cabbage. The expression of BrJUB1 was found to increase continuously during storage time, accompanied by an upregulation of chlorophyll catabolic genes (CCGs) and reduced chlorophyll content. Subcellular localisation and transactivation analyses in tobacco revealed that BrJUB1 possessed two characteristics of transcription factors: nuclear localisation and transactivation of gene activity. More importantly, electrophoretic mobility shift assay and dual-luciferase analysis demonstrated that BrJUB1 bound to NAC recognition sequence in the promoters of major CCGs including BrNYC1, BrPAO, BrPPH1 and BrSGR1, and activated their transcription. Taken together, these findings show that BrJUB1 might act as an important regulator in leaf senescence of post-harvest Chinese flowering cabbage through activating chlorophyll degradation. This study expands our understanding of molecular mechanisms involved in leaf senescence of harvested Chinese cabbage and possibly other leafy vegetables.