# The NAC Transcription Factors CjNAC43 and CjNAC54 Act as Positive Regulators of Leaf Senescence in Clerodendrum japonicum

## TL;DR

This study identifies two genes, CjNAC43 and CjNAC54, that promote leaf aging in the plant Clerodendrum japonicum, especially under stress conditions like darkness and abscisic acid exposure.

## Contribution

The novel contribution is the functional characterization of CjNAC43 and CjNAC54 as positive regulators of leaf senescence in C. japonicum.

## Key findings

- Overexpression of CjNAC43 and CjNAC54 in Arabidopsis accelerated leaf senescence and reduced chlorophyll content.
- Silencing these genes in C. japonicum delayed leaf senescence.
- Both genes increased plant sensitivity to abscisic acid and darkness, promoting senescence under these conditions.

## Abstract

Leaf senescence is a crucial developmental process in plants, and is tightly regulated by transcription factors such as NAC family members. However, the functions of NAC genes in the leaf senescence of the medicinal and ornamental plant Clerodendrum japonicum remain largely uncharacterized. In this study, we performed the transcriptome sequencing of mature and early-senescent leaves in C. japonicum. We screened candidate NAC genes and validated their expression patterns using quantitative real-time PCR (qRT-PCR). The functions of CjNAC43 and CjNAC54 were characterized through heterologous overexpression in Arabidopsis thaliana and Virus-Induced Gene Silencing (VIGS) in C. japonicum. We further investigated their roles in abscisic acid (ABA)- and dark-induced senescence. Our findings revealed that transcriptomic analysis identified 522 differentially expressed genes, including nine NAC members. CjNAC43 and CjNAC54 exhibited significantly upregulated expression during the critical senescence phase (90–130 days). Overexpression of either gene in A. thaliana accelerated leaf senescence, up-regulated senescence-associated genes (SAGs), and reduced chlorophyll content. Conversely, silencing CjNAC43 or CjNAC54 in C. japonicum delayed senescence. Both genes enhanced the plant’s sensitivity to ABA and darkness, leading to accelerated senescence under these stresses. In conclusion, our results demonstrate that CjNAC43 and CjNAC54 function as positive regulators of leaf senescence in C. japonicum, partly by mediating ABA and dark signaling pathways.