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

Abstract

Catalase (CAT) is one of the key enzymes involved in antioxidant defense systems and mainly scavenges H2O2 and plays a vital role in plant growth, development, and various adverse stresses. To date, a systematic study of the CAT gene family in rubber tree has not been reported. In this study, five HbCAT 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 HbCAT 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 HbCAT family based on Ka/Ks values. Analysis of cis-acting elements in the promoters indicated that HbCAT 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 HbCATs gradually increased with leaf development and were highly expressed in mature leaves. Gene expression profiling exhibited the differential expression of the HbCATs under cold, heat, drought, and NaCl stresses. Our results provide comprehensive information about the HbCAT gene family, laying the foundation for further research on its function in rubber tree.