Vanadium-Dependent Haloperoxidase Gene Evolution in Brown Algae: Evidence for Horizontal Gene Transfer

Area of Science:

• Marine Biology
• Evolutionary Genomics
• Biochemistry

Background:

• Brown algae accumulate iodine, a trait linked to vanadium-dependent haloperoxidase (V-HPO) enzymes essential for iodine synthesis.
• The evolutionary origins and genomic dynamics of V-HPO genes in brown algae are not well understood.

Purpose of the Study:

• To investigate the genomic and evolutionary history of V-HPO genes in brown algae, specifically focusing on Laminariales species like Saccharina japonica.
• To elucidate the mechanisms driving the expansion and diversification of V-HPO gene families in brown algae.

Main Methods:

• Genomic analysis of V-HPO gene families in brown algae.
• Phylogenetic analysis to determine evolutionary relationships between algal and bacterial V-HPOs.
• Identification and analysis of transposable elements associated with V-HPO gene clusters.
• Gene expression profiling under varying environmental conditions.

Main Results:

• Brown algae exhibit a significant expansion of the V-HPO gene family, with 88 V-HPOs identified in Saccharina japonica.
• Phylogenetic analyses indicate that brown algal V-HPOs are closely related to bacterial V-HPOs, particularly from Acidobacteriota.
• Active transposable elements are enriched near V-HPO gene clusters, suggesting their role in gene duplication and horizontal gene transfer.
• V-HPO gene expression is dynamically regulated in response to environmental factors.

Conclusions:

• Horizontal gene transfer (HGT) from bacteria, especially Acidobacteriota, has been a major driver in the acquisition and expansion of V-HPO genes in brown algae.
• Transposable elements facilitate V-HPO gene duplication and HGT, contributing to kelp genomic adaptation.
• These genomic adaptations enhance brown algae's ecological success in iodine-rich coastal environments and provide insights into marine evolutionary processes.