Genome-wide identification of xyloglucan endotransglucosylase/hydrolase genes in almond and PdXTH2 overexpression induces cell structural disassembly and promotes programmed cell death progression.

The xyloglucan endotransglucosylase/hydrolase (XTH) gene family plays a crucial role in fruit development and texture regulation. We used the telomere-to-telomere genome of 'Wanfeng' almond to identify and analyse the XTH gene family, examining protein physicochemical properties, phylogenetic relationships, protein conserved motifs, gene structure, gene replication, and expression patterns. We identified 23 PdXTH family members through the telomere-to-telomere level genome of 'Wanfeng' almond. These genes exhibited significant variations in protein physicochemical properties, gene structure, and sequence conservation. PdXTH genes were predominantly distributed in the I/II subfamily and demonstrated high sequence conservation and gene structure similarity. Gene duplication events contributed to an increase in PdXTH family members. Analysis of cis-acting elements suggest that PdXTH genes are involved in almond growth and development, stress response, and hormone regulation. Expression patterns revealed that PdXTH genes display significant tissue-specific expression. PdXTH genes had notable temporal gradient changes during fruit development and may function at different development stages. The sustained high expression of PdXTH genes throughout almond fruit development represents a potential mechanism for maintaining fruit firmness. Furthermore, transgene studies confirmed that PdXTH2 has a regulatory role in programmed cell death. PdXTH2 is localized to the cell membrane. PdWRKY24 and PdbHLH92 can directly bind to the PdXTH2 promoter region and positively regulate its transcriptional activity. In conclusion, this study provides new insights into the role of the XTH family in plant physiology.