Genome-Wide Identification and Expression Analysis of the GRAS Gene Family and Their Responses to Heat Stress in Cymbidium goeringii

The GRAS gene family, responsible for encoding transcription factors, serves pivotal functions in plant development, growth, and responses to stress. The exploration of the GRAS gene family within the Orchidaceae has been comparatively limited, despite its identification and functional description in various plant species. This study aimed to conduct a thorough examination of the GRAS gene family in Cymbidum goeringii, focusing on its physicochemical attributes, phylogenetic associations, gene structure, cis-acting elements, and expression profiles under heat stress. The results show that a total of 54 CgGRASs were pinpointed from the genome repository and categorized into ten subfamilies via phylogenetic associations. Assessment of gene sequence and structure disclosed the prevalent existence of the VHIID domain in most CgGRASs, with around 57.41% (31/54) CgGRASs lacking introns. The Ka/Ks ratios of all CgGRASs were below one, indicating purifying selection across all CgGRASs. Examination of cis-acting elements unveiled the presence of numerous elements linked to light response, plant hormone signaling, and stress responsiveness. Furthermore, CgGRAS5 contained the highest quantity of cis-acting elements linked to stress response. Experimental results from RT-qPCR demonstrated notable variations in the expression levels of eight CgGRASs after heat stress conditions, particularly within the LAS, HAM, and SCL4/7 subfamilies. In conclusion, this study revealed the expression pattern of CgGRASs under heat stress, providing reference for further exploration into the roles of CgGRAS transcription factors in stress adaptation.