EjNAC3 transcriptionally regulates chilling-induced lignification of loquat fruit via physical interaction with an atypical CAD-like gene

Lignin is an important component of many plant secondary cell walls. In the fruit of loquat (Eriobotrya japonica), lignification of cell walls in the fleshy tissue occurs when fruit are subjected to low-temperature storage, which is commonly used to avoid the rapid senescence that occurs at room temperature. In this study, two NAC domain genes, EjNAC3 and EjNAC4, were isolated and shown to be significantly induced at 0 °C, which was concomitant with an increase in the fruit lignification index. Lignification and expression of both EjNAC3 and EjNAC4 were inhibited by low-temperature conditioning and by heat treatment. In addition, EjNAC3 trans-activated the lignin biosynthesis-related EjCAD-like promoter, which was measured using a dual-luciferase assay. Further analysis with yeast one-hybrid and electrophoretic mobility shift assays indicated that EjNAC3 could physically bind to the promoter of the EjCAD-like gene. Thus, EjNAC3 is a direct regulator of loquat chilling-induced lignification, via regulations of EjCAD-like.