College of Agriculture and Biotechnology, Zhejiang University, Zijingang Campus, Hangzhou 310058, China.
Zhejiang Provincial Key Laboratory of Horticultural Plant Integrative Biology, Zhejiang University, Zijingang Campus, Hangzhou 310058, China.
J Exp Bot. 2024 Oct 30;75(20):6625-6643. doi: 10.1093/jxb/erae333.
Changes in both lignin biosynthesis and DNA methylation have been reported to be associated with chilling stress in plants. When stored at low temperatures, red-fleshed loquat is prone to lignification, with increased lignin content and fruit firmness, which has deleterious effects on taste and eating quality. Here, we found that 5 °C storage mitigated the increasing firmness and lignin content of red-fleshed 'Dahongpao' ('DHP') loquat fruit that occurred during 0 °C storage. EjNAC5 was identified by integrating RNA sequencing with whole-genome bisulfite sequencing analysis of 'DHP' loquat fruit. The transcript levels of EjNAC5 were positively correlated with changes in firmness and negatively correlated with changes in DNA methylation level of a differentially methylated region in the EjNAC5 promoter. In white-fleshed 'Baisha' ('BS') loquat fruit, which do not undergo chilling-induced lignification at 0 °C, the transcripts of EjNAC5 remained low and the methylation level of the differentially methylated region in the EjNAC5 promoter was higher, compared with 'DHP' loquat fruit. Transient overexpression of EjNAC5 in loquat fruit and stable overexpression in Arabidopsis and liverwort led to an increase in lignin content. Furthermore, EjNAC5 interacts with EjERF39 and EjHB1 and activates the transcription of Ej4CL1 and EjPRX12 genes involved in lignin biosynthesis. This regulatory network involves different transcription factors from those involved in the lignification pathway. Our study indicates that EjNAC5 promoter methylation modulates EjNAC5 transcript levels and identifies novel EjNAC5-EjERF39-Ej4CL1 and EjNAC5-EjHB1-EjPRX12 regulatory modules involved in chilling induced-lignification.
已报道植物冷胁迫与木质素生物合成和 DNA 甲基化的变化有关。低温贮藏时，红肉枇杷易木质化，木质素含量和果实硬度增加，对口感和食用品质有不利影响。在这里，我们发现 5°C 贮藏减轻了 0°C 贮藏过程中红肉 '大红袍'（'DHP'）枇杷果实硬度和木质素含量的增加。通过整合 'DHP' 枇杷果实的 RNA 测序和全基因组亚硫酸氢盐测序分析，鉴定出 EjNAC5。EjNAC5 的转录水平与硬度变化呈正相关，与 EjNAC5 启动子差异甲基化区域的 DNA 甲基化水平变化呈负相关。在 0°C 下不会发生冷诱导木质化的白皮 '白沙'（'BS'）枇杷果实中，EjNAC5 的转录物水平较低，EjNAC5 启动子差异甲基化区域的甲基化水平较高，与 'DHP' 枇杷果实相比。EjNAC5 在枇杷果实中的瞬时过表达和在拟南芥和地钱中的稳定过表达导致木质素含量增加。此外，EjNAC5 与 EjERF39 和 EjHB1 相互作用，并激活参与木质素生物合成的 Ej4CL1 和 EjPRX12 基因的转录。该调控网络涉及与木质化途径不同的转录因子。我们的研究表明，EjNAC5 启动子甲基化调节 EjNAC5 转录物水平，并确定了参与冷诱导木质化的新的 EjNAC5-EjERF39-Ej4CL1 和 EjNAC5-EjHB1-EjPRX12 调控模块。
