Comprehensive Analysis of the Catalase ( CAT ) Gene Family and Expression Patterns in Rubber Tree ( Hevea brasiliensis ) under Various Abiotic Stresses and Multiple Hormone Treatments

Catalase (CAT) is one of the key enzymes involved in antioxidant defense systems and mainly scavenges H O and plays a vital role in plant growth, development, and various adverse stresses. To date, a systematic study of the gene family in rubber tree has not been reported. In this study, five gene family members were identified from the rubber tree genome, and these were mainly clustered into two subfamilies. Gene structure and motif analysis showed that exon-intron and motif patterns were conserved across different plant species. Sequence analysis revealed that proteins contain one active catalytic site, one heme-ligand signature sequence, three conserved amino acid residues (His, Tyr, and Asn), and one peroxisome-targeting signal 1 (PTS1) sequence. Fragment duplication is a selection pressure for the evolution of the family based on Ka/Ks values. Analysis of cis-acting elements in the promoters indicated that gene expression might be regulated by abscisic acid (ABA), salicylic acid (SA), and MYB transcription factors; furthermore, these genes might be involved in plant growth, development, and abiotic stress responses. A tissue-specific expression analysis showed that s gradually increased with leaf development and were highly expressed in mature leaves. Gene expression profiling exhibited the differential expression of the under cold, heat, drought, and NaCl stresses. Our results provide comprehensive information about the gene family, laying the foundation for further research on its function in rubber tree.