Three stress-responsive NAC transcription factors, Pp-SNACs, differentially and synergistically regulate abiotic stress in pear

NAC proteins contribute to regulate diverse plant developmental processes and tolerances to biotic and abiotic stresses. In pear, limited reports are available about the transcriptional regulations of PpNACs during abiotic stress signaling. The transcriptome of Pyrus ussuriensis in response to cold stress (4. C) for 5 h and 12 h revealed some differentially expressed NAC genes. We found three putative NAC genes, PpNAC88, PpNAC92, and PpNAC130, from subgroup-3D (stress responsive NAC subgroup in pear) that were differentially expressed during cold stress in pear. At the same time, RNA-seq of Pyrus betulaefolia under salt stress also revealed high RPKM values of these Pp-NACs. Further, these PpNACs, PpNAC88/92/130, were named Pp-SNACs due to their phylogenetic group with well-known SNACs (stress-responsive NACs) in other crops. qRT-PCR revealed that all Pp-SNACs were significantly and differentially expressed in response to cold and salt stresses, similar to stressresponsive genes, PpCOR47/15A/RD29A/KIN. High transcript abundances of all PpSNACs along with the PpABF2/ABF3/RD29A/COR15A (ABA and stress-responsive genes) were also observed during ABA treatment to both pear calli and explants. Furthermore, luciferase and Y1H assays revealed the transcriptional regulations of Pp-SNACs on PpCOR47/15A/RD29A promoters, while PpNAC88 and PpNAC130 both, in-vivo and in-vitro, can regulate the promoter of PpCOR15A. Conversely, we also found that PpNAC88 and PpNAC130 also make protein complex, and the combination of PpNAC88 and PpNAC130 synergistically regulates the PpCOR15A promoter, which may highlight multidirectional regulations of these Pp-SNACs during abiotic stress in the pear.