Genome-wide analysis of TGACG motif-binding factor (TGA) family and mechanism of PpTGA2.1-L and PpTGA7-L response to salicylic acid regulating fruit senescence through interaction with PpNPR1 in sand pear

Abstract

Sand pear fruit are well-regarded for their rich nutritional content and desirable flavor. Despite their popularity, their limited postharvest longevity poses a challenge for commercial distribution. Research has demonstrated that salicylic acid (SA) can effectively slow down fruit senescence processes and enhance storage duration. However, there is limited research on the interaction between TGA proteins and the SA receptor protein NPR1 in the regulation of fruit senescence. In this study, 14 TGA genes were identified in sand pear. Transcriptomic analysis revealed two genes (PpTGA2.1-L and PpTGA7-L). The 14 TGA proteins in sand pear were divided into five subgroups. PpTGA2.1-L and PpTGA7-L exhibited distinct expression patterns across various sand pear tissues, with both genes showing preferential expression levels during the fruit senescence stage. Exogenous SA treatment up-regulated the expression of PpTGA2.1-L while down-regulating the expression of PpTGA7-L. Further experiments using yeast two-hybrid and luciferase assays confirmed that both PpTGA2.1-L and PpTGA7-L interact with PpNPR1. Functional analysis revealed that PpTGA2.1-L delayed sand pear fruit senescence, whereas PpTGA7-L had the opposite effect. Further investigations demonstrated that PpTGA2.1-L, in coordination with the SA receptor NPR1, enhances the activities of antioxidant enzymes peroxidase, superoxide dismutase, and catalase, increases the content of SA, while reducing the accumulation of malondialdehyde, ethylene, polygalacturonase, pectin methyl ester, and cellulase, thus delaying fruit senescence. SA treatment further delays fruit senescence. In contrast, PpTGA7-L modulates the senescence process by antagonizing the action of PpNPR1. This senescence process was delayed after SA treatment. In conclusion, the results of this study revealed that PpTGA2.1-L and PpTGA7-L play key roles in pear fruit senescence by interacting with PpNPR1 through the SA signaling pathway.