The transcription factor EjNAC5 regulates loquat fruit chilling lignification

Area of Science:

• Plant Biology
• Molecular Biology
• Agricultural Science

Background:

• Chilling stress impacts plant physiology, often leading to undesirable changes like lignification in fruits.
• Red-fleshed loquat fruit exhibits increased firmness and lignin content under cold storage, negatively affecting eating quality.
• DNA methylation and lignin biosynthesis are implicated in plant responses to environmental stresses.

Purpose of the Study:

• To investigate the molecular mechanisms underlying chilling-induced lignification in red-fleshed loquat fruit.
• To identify key genes and regulatory pathways involved in controlling fruit firmness and lignin accumulation during cold storage.
• To explore the role of DNA methylation in regulating chilling-induced lignification.

Main Methods:

• Integrated RNA sequencing and whole-genome bisulfite sequencing analysis of loquat fruit under different storage temperatures (0 °C vs. 5 °C).
• Identification and characterization of the EjNAC5 gene and its promoter region.
• Gene expression analysis, transient and stable overexpression experiments in loquat, Arabidopsis, and liverwort, and protein-protein interaction assays.

Main Results:

• 5 °C storage effectively mitigated the increase in firmness and lignin content observed at 0 °C in 'Dahongpao' loquat fruit.
• EjNAC5 transcript levels positively correlated with fruit firmness and negatively with promoter DNA methylation levels.
• Overexpression of EjNAC5 increased lignin content; EjNAC5 interacts with EjERF39 and EjHB1, activating lignin biosynthesis genes (Ej4CL1, EjPRX12).

Conclusions:

• EjNAC5 is a crucial transcription factor regulating chilling-induced lignification in loquat fruit.
• Epigenetic regulation via EjNAC5 promoter methylation modulates its transcript levels and subsequent lignin biosynthesis.
• Novel regulatory modules (EjNAC5-EjERF39-Ej4CL1 and EjNAC5-EjHB1-EjPRX12) are identified in the chilling-induced lignification pathway.