Abstract:To explore the role of NAC transcription factors (TFs) in the progress of the retrieved green of Fe-deficiency chlorotic leaves in ‘Dangshansuli’ pear (Pyrus bretschneideri Rehd.), PbrNAC TFs were screened in the pear leaves, and the expression patterns of key PbrNACs in response to the retrieved green progress were analyzed. In this study, normal leaves (N) and chlorotic leaves (C) of ‘Dangshansuli’ pear were taken as test material, and exogenous 0.2% FeSO4 (2 g/L FeSO4) solution was sprayed on C during the growing season to confirm its effect and Fe2+ accumulation in C, with N and C treated with distilled water as the control (CN and CC). We have studied the biological properties, tissue-specific expression, and response patterns of the key PbrNAC in this progress. Moreover, the correlation analysis between the expression of PbrNAC with Fe2+ content was carried out. The results showed, (1) A total of 21 PbrNAC genes with typical NAM domain were significantly differently expressed between N and C, which could be clustered into 7 subclasses with fewer introns and with motifs ranging from 4 to 9. (2) Most of the PbrNAC genes preferred to express in the roots, and all the genes could respond to the retrieved green progress of C. Among them, the expression levels of the seven genes named Pbr032231.1/Pbr021393.1/Pbr026635.1/Pbr038615.1/Pbr019210.3/Pbr019212.1/Pbr002372.1 was significantly lower in CC than that in CN, and after FeSO4 treatment, their expression was significantly increased compared to that of CC; In contrast, the expression levels of 14 PbrNAC genes, including Pbr007284.1/Pbr016205.1/Pbr007673.1, were notably higher in CC than that in CN, and after FeSO4 treatment, they were more likely to increase with statistical differences. (4) The Fe2+ content in leaves was significantly negatively associated with the expression of Pbr007284.1/Pbr016205.1/Pbr007673.1. Although other NAC TFs did not show a direct linkage with the Fe2+ accumulation, there is a certain relationship between them and Pbr007284.1/Pbr016205.1/Pbr007673.1, such as Pbr016932.1/Pbr027956.1/Pbr029956.1/Pbr026635.1. (4) Consistent with the difference in the transcript level in aboveground leaves, the expression of Pbr007284.1/Pbr016205.1/Pbr007673.1 homologs in roots of normal pear trees were also prominently higher than that in roots of chlorotic pear trees, implying a synergistic regulatory effect. Overall, PbrNAC genes may be related to the retrieved green progress of CC, and may be involved in Fe deficiency response in pear, where Pbr007284.1, Pbr016205.1, and Pbr007673.1 might play a vital regulatory role.