BrTCP7 Transcription Factor Is Associated with MeJA-Promoted Leaf Senescence by Activating the Expression of BrOPR3 and BrRCCR.

Yan-Mei Xu,Xian-Mei Xiao,Ze-Xiang Zeng,Zong-Li Liu,Jian-Ye Chen,Xiao-Li Tan,Xin-Guo Su,Jian-Wen Chen

doi:10.3390/ijms20163963

Abstract

The plant hormone jasmonic acid (JA) has been recognized as an important promoter of leaf senescence in plants. However, upstream transcription factors (TFs) that control JA biosynthesis during JA-promoted leaf senescence remain unknown. In this study, we report the possible involvement of a TEOSINTE BRANCHED1/CYCLOIDEA/PCF (TCP) TF BrTCP7 in methyl jasmonate (MeJA)-promoted leaf senescence in Chinese flowering cabbage. Exogenous MeJA treatment reduced maximum quantum yield (Fv/Fm) and total chlorophyll content, accompanied by the increased expression of senescence marker and chlorophyll catabolic genes, and accelerated leaf senescence. To further understand the transcriptional regulation of MeJA-promoted leaf senescence, a class I member of TCP TFs BrTCP7 was examined. BrTCP7 is a nuclear protein and possesses trans-activation ability through subcellular localization and transcriptional activity assays. A higher level of BrTCP7 transcript was detected in senescing leaves, and its expression was up-regulated by MeJA. The electrophoretic mobility shift assay and transient expression assay showed that BrTCP7 binds to the promoter regions of a JA biosynthetic gene BrOPR3 encoding OPDA reductase3 (OPR3) and a chlorophyll catabolic gene BrRCCR encoding red chlorophyll catabolite reductase (RCCR), activating their transcriptions. Taken together, these findings reveal that BrTCP7 is associated with MeJA-promoted leaf senescence at least partly by activating JA biosynthesis and chlorophyll catabolism, thus expanding our knowledge of the transcriptional mechanism of JA-mediated leaf senescence.

Highlights

As one of the major leafy vegetables, Chinese flowering cabbage
We identified and characterized several transcription factors (TFs) including BrWRKY65 [1], BrWRKY6 [2], BrERF72 [5], and BrNAC055 [6] involved in leaf senescence in Chinese flowering cabbage, of which BrERF72 was shown to enhance jasmonic acid (JA) accumulation by inducing the expression of three JA biosynthetic genes (BrLOX4, BrAOC3, and BrOPR3) during methyl jasmonate (MeJA)-promoted leaf senescence [5]
The current study revealed that a TEOSINTE BRANCHED1/CYCLOIDEA/PCF (TCP), TF BrTCP7, is positively associated with MeJA-promoted leaf senescence by the direct transcriptional activation of a JA biosynthetic gene BrOPR3 and a catabolic genes (CCGs) BrRCCR

Summary

Introduction

As one of the major leafy vegetables, Chinese flowering cabbage Parachinensis) is a popular in the Asian diet due to its health-promoting compounds and valuable anticancer properties [1,2,3]. Flowering shoots, stems, and younger leaves of this cabbage are harvested for eating. Harvested cabbage leaves senesce rapidly during transportation and storage, wilt, and yellow, reducing product quality and commercial value [4,5,6]. There is a demand for the elucidation of the molecular mechanisms of leaf senescence of Chinese flowering cabbage. Such knowledge is important for developing practical solutions to maintain the quality and extend the shelf-life of this vegetable

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Results

Conclusion