Genome-wide identification and comprehensive characterization of the TGA gene family in pear fruit and their potential roles in response to Alternaria alternata infection

The black spot, caused by Alternaria alternata, represents a globally significant disease affecting pear fruit production. TGACG motif-binding factor (TGA) transcription factors, which are members of the basic region leucine zipper (bZIP) family, play a vital role in the defense mechanisms of plants against pathogens. This study systematically screened and characterized TGA genes in pears, and further investigated their potential roles in response to A. alternata infection. The results demonstrated that pears possess 10 TGA genes, which are distributed across 9 chromosomes and located in the nucleus. Phylogenetic analysis revealed that the 10 TGA genes can be classified into five distinct groups, each characterized by consistent structural features and motif compositions. The prediction of cis-regulatory elements indicates that PbTGAs are involved in responses to various hormones and environmental stimuli, as well as in growth and developmental processes. In addition, RT-qPCR analysis demonstrated that PbTGA2.2, PbTGA2.3, PbTGA4, PbTGA7, PbTGA9, and PbTGA10 showed significant changes in expression levels following A. alternata infection. Furthermore, A. alternata infection was found to up-regulate the expression levels of PbWRKY11/12/31/33, PbICS2, PbEPS1, PbEDS5, PbPBS3, PbNPR1, and PbPR-1 in Snow pear fruit. These results indicate that PbTGA genes play a role in the salicylic acid signaling pathway, contributing to resistance against A. alternata in pears.