Liang Zihao, Shi Yanna, Huang Yiqing, Lu Jiao, Zhang Mengxue, Cao Xizhi, Hu Ruoqian, Li Dongdong, Chen Wenbo, Zhu Changqing, Wu Di, Chen Kunsong
College of Agriculture and Biotechnology, Zhejiang University, Zijingang Campus, Hangzhou 310058, China.
College of Agriculture and Biotechnology, Zhejiang University, Zijingang Campus, Hangzhou 310058, China; Zhejiang Key Laboratory of Horticultural Crop Quality Improvement, Zhejiang University, Zijingang Campus, Hangzhou 310058, China; The State Agriculture Ministry Laboratory of Horticultural Plant Growth and Development, Zhejiang University, Zijingang Campus, Hangzhou 310058, China.
J Adv Res. 2025 Jul;73:93-104. doi: 10.1016/j.jare.2024.08.032. Epub 2024 Sep 2.
Lignin is a principal constituent of the secondary cell wall, which plays a role in both plant growth and defensing against stress, such as low temperature and pest infestation. Additionally, it also accumulates in fleshy fruits and negatively affects fruit quality. Red-fleshed loquat is temperature sensitive and exhibits cold-induced lignification. A number of technologies have been developed, for example, Low Temperature Conditioning (LTC) treatment, which has been applied in order to relieve the symptom of cold injury.
The present study seeks to elucidate the regulatory mechanism underlying cold-induced lignification in loquat fruit.
The target genes were isolated through the analysis of transcriptome. The gene function was analyzed by transient transgenic method in tobacco leaves and loquat fruit, respectively, as well as stable overexpression in liverwort. The regulatory mechanism study was achieved by in vitro protein-protein interaction assays, dual-luciferase assay, and EMSA.
In the present study, the Xylem NAC Domain transcription factor EjXND1 was identified as a repressor of loquat fruit lignification. It was demonstrated that EjXND1 could interact with the characterized lignin activator EjHB1, resulting in a diminution of the activation of EjHB1 on EjPRX12 promoter. Furthermore, two highly methylated regions were identified in the promoter of EjXDN1. One of these regions exhibited a negative correlation between methylation level and EjXND1 expression. Additionally, it was shown that hypermethylation of this region weaken the binding affinity of EjXND1 activators to its promoter.
The EjXND1 plays a role in modified Low Temperature Conditioning (mLTC) treatment that alleviates cold-induced lignification in red-fleshed loquat fruit by targeting the EjHB1-EjPRX12 module and EjXND1 is regulated by the dynamic of DNA methylation level in the promoter.
木质素是次生细胞壁的主要成分，在植物生长以及抵御低温和虫害等胁迫方面发挥作用。此外，它也会在肉质果实中积累，对果实品质产生负面影响。红肉枇杷对温度敏感，会出现冷诱导木质化现象。人们已经开发了多种技术，例如低温预处理（LTC）处理，用于缓解冷害症状。
本研究旨在阐明枇杷果实冷诱导木质化的调控机制。
通过转录组分析分离目标基因，并分别采用烟草叶片和枇杷果实的瞬时转基因方法以及地钱中的稳定过表达来分析基因功能；通过体外蛋白质-蛋白质相互作用试验、双荧光素酶试验和电泳迁移率变动分析来研究调控机制。
在本研究中，木质部NAC结构域转录因子EjXND1被鉴定为枇杷果实木质化的抑制因子。研究表明，EjXND1可与已鉴定的木质素激活因子EjHB1相互作用，导致EjHB1对EjPRX12启动子的激活作用减弱。此外，在EjXDN1启动子中鉴定出两个高度甲基化区域。其中一个区域的甲基化水平与EjXND1表达呈负相关。此外，该区域的高甲基化削弱了EjXND1激活因子与其启动子的结合亲和力。
EjXND1在改良低温预处理（mLTC）处理中发挥作用，通过靶向EjHB1-EjPRX12模块减轻红肉枇杷果实的冷诱导木质化，并且EjXND1受启动子中DNA甲基化水平动态变化的调控。
