Estudo dos padrões evolutivos de genes órfãos em plantas terrestres

Abstract

Orphan genes (OGs), sequences with no detectable homologs in other species, represent an intriguing evolutionary puzzle and a source of genomic innovation. However, despite their importance, the identification and characterization of OGs in land plants remain limited, and a comprehensive, integrated study addressing diverse plant species is necessary. This study investigates the evolutionary patterns of OGs in 22 representative embryophyte species using a comparative genomics approach. Bioinformatics tools were applied for OG identification, followed by structural, compositional, and gene expression analyses. The results revealed remarkable variation in OG proportions across lineages, ranging from 1% in Camelina sativa to 33% in Ceratodon purpureus. This disparity suggests that factors such as speciation rates and ecological pressures may influence OG retention. Structural analyses demonstrated that orphan genes are significantly shorter, with fewer introns and longer exons compared to conserved genes. Additionally, OGs exhibited higher GC content, a pattern potentially linked to thermodynamic stability or their location in recombination-rich chromosomal regions. Transcriptome analysis of A. thaliana highlighted that expressed OGs tended to be more compact (fewer introns and larger exons) than their silent counterparts, supporting the hypothesis that structural simplicity favors integration into transcriptional networks. Thus, this work advances our understanding of orphan gene dynamics in plants, demonstrating that their prevalence varies according to lineage-specific evolutionary history and that their structural features reflect recent origins. Future directions include integrating epigenomic data to explore regulatory mechanisms and expanding research to non-model species, such as ferns, where OG evolution remains poorly understood.