Identification and characterization of GRAS genes in passion fruit (Passiflora edulis Sims) revealed their roles in development regulation and stress response.

Abstract

Key message: Twenty-nine GRAS genes were identified in passion fruit, the N-terminal regions and 3D (three-dimensional) structures were closely related with their tissue-specific expression patterns. Candidate PeGRASs for enhancing stress resistance were identified. Passion fruit (Passiflora edulis Sims) is a tropical fruit crop with significant edible and ornamental value, but its growth and development are highly sensitive to environmental conditions. The plant-specific GRAS gene family plays critical roles in regulating growth, development, and stress responses. Here, we performed the first comprehensive analysis of the GRAS gene family in passion fruit. A total of 29 GRAS genes were identified and named PeGRAS1 to PeGRAS29 based on their chromosomal locations. Phylogenetic analysis using GRAS proteins from passion fruit, Arabidopsis, and rice revealed that PeGRAS proteins could be classified into 10 subfamilies. Compared to Arabidopsis, passion fruit lacked members from the LAS subfamily but gained one GRAS member (PeGRAS9) clustered with the rice-specific Os4 subfamily. Structural analysis performed in silico revealed that most PeGRAS members were intron less and exhibited conserved motif patterns near the C-terminus, while the N-terminal regions varied in sequence length and composition. Members within certain subfamilies including DLT, PAT1, and LISCL with similar unstructured N-terminal regions and 3D structures, exhibited similar tissue-specific expression patterns. While PeGRAS members with difference in these structural features, even within the same subfamily (e.g., DELLA), displayed distinct expression patterns. These findings highlighted that the N-terminal regions of GRAS proteins may be critical for their specific functions. Moreover, many PeGRAS members, particularly those from the PAT1 subfamily, were widely involved in stress responses, with PeGRAS19 and PeGRAS26 likely playing roles in cold tolerance, and PeGRAS25 and PeGRAS28 in drought resistance. This study provides a foundation for further functional research on PeGRASs and offers potential candidates for molecular breeding aimed at enhancing stress tolerance in passion fruit.