GA binding of nematode Hsp-90 shows a life-history pattern: free-living nematodes and parasites with free-living environmental larval stages generally do not bind GA in pull-down assays, while obligate parasites and species whose environmental/free-living stage is enclosed in a resistant egg do bind GA.
Gene-wide codon model tests did not detect consistent positive selection, but branch-site methods identified lineage-specific positively selected sites.
Yet the authors report they cannot prove that selection is correlated with GA-binding status, and even residues in the GA-binding region do not cleanly differentiate binding vs non-binding species.
GA binding was measured with GA-bead pull-downs on worm lysates; for some species the GA-binding status is uncertain or stage-dependent (they explicitly flag stage availability and uncertainty for certain species).
Thus, the binding-life-history correlation is strongest, while the βadaptive sequence evolution explains bindingβ mechanism remains underdetermined.
The work is most useful as an evolutionary hypothesis generator: it prioritizes non-sequence determinants of GA sensitivity (e.g., chaperone complex/co-chaperone context, post-translational regulation, or structural dynamics) over a simple βmutate residues β gain/lose GA pocketβ model.
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