Seagrasses show ongoing loss of ethylene biosynthesis genes through pseudogene evidence
Researchers identified pseudogene remnants of ethylene biosynthesis genes (ACO and ACS) in four seagrass species, confirming that gene loss underlies the reduction of this pathway in aquatic plants. Some seagrass species showed complete absence of functional genes with no detectable pseudogenes, suggesting an ancient loss, while others showed active gene contraction still in progress. The findings suggest this adaptation is driven by submersion in water generally, rather than by the marine environment specifically.
A study posted to bioRxiv examined the genomic basis for the near-complete loss of ethylene biosynthesis in seagrasses, a group of flowering plants that returned to an aquatic lifestyle from terrestrial ancestors. By searching for pseudogenes — non-functional remnants of once-active genes — the researchers confirmed that the reduction in ACO and ACS gene copies is the result of genuine gene loss rather than other genomic mechanisms. In species where ethylene biosynthesis is completely absent, no pseudogenes were detected, implying the loss occurred so long ago that all traces have eroded away. In contrast, species still undergoing gene contraction retained identifiable pseudogenes, indicating the process is recent and potentially still ongoing. The team extended their analysis to Utricularia gibba, a submerged freshwater plant unrelated to seagrasses, and found a similarly reduced ACO and ACS gene complement, while closely related terrestrial species showed higher gene counts with no evidence of loss. This parallel reduction across independent aquatic lineages supports the hypothesis that submergence itself — not saltwater or marine conditions — is the key selective pressure driving ethylene pathway loss.
What's missing
The study is a preprint and has not yet undergone peer review, so findings should be treated as preliminary. The authors do not fully explain the functional consequences of ethylene loss for seagrass physiology or fitness, nor do they experimentally test whether submergence is causally responsible for the selective pressure. The evolutionary timescales inferred for 'ancient' versus 'recent' gene loss are not precisely quantified in the abstract. Additionally, the mechanism by which pseudogenes are identified and distinguished from other non-coding sequences is not detailed here, leaving methodological assumptions unexamined.
What different sources said
- bioRxivCenter
Pseudogenes confirm ongoing loss of ethylene biosynthesis in seagrasses
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