Cloning and expression analysis of the HbPPO2 gene in the latex of rubber tree clone Reyan 879

【Objective】 This study aimed to clone important genes in the latex polyphenol oxidase （PPO） gene family of the rubber tree clone Reyan 879 and analyze their expression patterns， so as to provide a reference for elucidating the mechanism by which HbPPO family genes participated in redox reactions， resistance， and stress responses of laticifer cells of rubber tree Reyan 879. 【Method】 The transcriptome data was analyzed to select and clone genes related to rubber production and flow in the HbPPO gene family of rubber tree clone Reyan 879. The selected gene was cloned， and the bioinformatics analysis was performed to investigate changes in relative expression and thiol content as well as the correlations between them. 【Result】 A new HbPPO family gene， HbPPO2 was identified and cloned through transcriptome data screening. The HbPPO2 gene encoded a non-secretory basic hydrophobic protein and contained one tyrosinase domain that was characteristic of the PPO family. The HbPPO2 promoters contained cis-acting elements associated with hormone response， stress response， and light response； among elements of stress response and hormone response， those of anaerobic induction and methyl jasmonate response had the highest numbers. The HbPPO2 protein exhibited strong interactions with 10 other proteins. These 10 proteins that interacted with the HbPPO2 protein belonged to copper-containing amine oxidase， glutamic-oxaloacetic transaminase， tyrosine decarboxylase， phenylacetaldehyde synthase， and potential transa-minases. The genes encoding HbPPO2 interacting protein were primarily enriched in signaling pathways related to processes such as cellular amino acid metabolism， organic nitrogen compound metabolism， and peroxisome. As the tapping frequency decreased， the relative expression of the HbPPO2 gene significantly declined （P<0.05）， and latex thiol content also gradually decreased. The correlation coefficient between latex thiol content and the relative expression of the HbPPO2 gene was 0.87， indicating a strong correlation. 【Conclusion】 The HbPPO2 gene exhibits a significantly decreased expression as the tapping frequency reduces， indicating that the gene may influence latex thiol content by regulating reactive oxygen species metabolism in rubber tree laticifer cells， and thus play a crucial role in the physiological processes of rubber production and flow.