Genome-Wide Identification and Expression Analysis of GASA Genes in <em>Hevea brasiliensis</em> Reveals their Involvement in Response to Cold Stress

The Gibberellic Acid-Stimulated in Arabidopsis (GASA) gene family, a plant-specific transcription factor family, is regulated by gibberellins and plays a crucial role in regulating plant growth and development. To further explore the functions of GASA genes in Hevea brasiliensis, based on the rubber tree genome data, 18 HbGASA genes were identified and named HbGASA1 to HbGASA18. Bioinformatics approaches were utilized to conduct a comprehensive analysis of the gene structure, chromosome distribution, protein structure, phylogenetic evolution, and expression profiles of these genes. Subsequently, the expression of selected genes was investigated by quantitative real-time polymerase chain reaction (qRT-PCR) under low-temperature stress. The results demonstrated that the 18 HbGASA genes were distributed across 10 chromosomes. The encoded proteins ranged from 88 to 253 amino acids in length, and the number of exons varied from 2 to 4. Phylogenetic tree analysis indicated that the HbGASA genes could be classified into three groups. The 18 members of the HbGASA gene family contained 10 motifs, among which Motif1 and Motif2 were relatively conserved in this gene family. Promoter analysis of HbGASA genes revealed the presence of multiple cis-acting elements related to hormone and stress responses. Transcripts of the 18 HbGASA genes were detected in various tissues, and significant differences were observed in their expression levels. In addition, qRT-PCR results showed that multiple HbGASA genes were significantly up-regulated under low-temperature stress. This study provides valuable insights into the structure, evolution, and function of GASA genes in the important tropical crop, Hevea brasiliensis.