Genome-wide characterization of the BBX gene family in perennial ryegrass and functional insights into the potentiality of LpBBX3 in drought and salt tolerance.

B-box (BBX) proteins, a subfamily of zinc-finger transcription factors, play a crucial role in regulating various physiological and developmental processes in plants, as well as in mediating stress responses. However, comprehensive characterization of the BBX gene family in perennial ryegrass has not been performed, and their potential functions in response to abiotic stress remain unclear. In the present study, we systematically identified 26 BBX genes in the perennial ryegrass genome and classified them into five distinct groups based on their phylogenetic relationships. These classifications were further supported by their gene structures and conserved protein motifs. Collinearity analysis revealed that segmental duplication events have been a primary driver for the expansion of the LpBBX family, with duplicated genes exhibiting strong signatures of purifying selection throughout evolution. Numerous cis-regulatory elements associated with hormonal signaling and abiotic stress response were identified in the promoter regions of LpBBXs. Transcription factor regulatory network analysis predicted several key families, including ERF, MYB, and NAC, as potential upstream regulators of LpBBX genes. Transcriptome analysis showed that LpBBXs exhibited diverse expression patterns in different tissues and responded positively to drought stress. Finally, functional analysis revealed that LpBBX3 possessed transcriptional activation activity and was localized in the nucleus. Heterologous expression of LpBBX3 significantly improved both drought and salt tolerance of yeast cells. These findings provide valuable genetic resources and insight into the LpBBX family, laying a crucial foundation for elucidating their biological functions in abiotic stress adaptation mechanisms in perennial ryegrass.