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The plastid-targeted transcription factorWhirly1(WHY1) has been implicated in chloroplast biogenesis, plastid genome stability, and fungal defense response, which together represent characteristics of interest for the study of autotrophic losses across the angiosperms. While gene loss in the plastid and nuclear genomes has been well studied in mycoheterotrophic plants, the evolution of the molecular mechanisms impacting genome stability is completely unknown. Here, we characterize the evolution ofWHY1in four early transitional mycoheterotrophic orchid species in the genusCorallorhizaby synthesizing the results of phylogenetic, transcriptomic, and comparative genomic analyses withWHY1genomic sequences sampled from 21 orders of angiosperms. We found an increased number of non-canonicalWHY1isoforms assembled from all but the greenestCorallorhizaspecies, including intron retention in some isoforms. WithinCorallorhiza, phylotranscriptomic analyses revealed the presence of tissue-specific differential expression ofWHY1in only the most photosynthetically capable species and a coincident increase in the number of non-canonicalWHY1isoforms assembled from fully mycoheterotrophic species. Gene- and codon-level tests ofWHY1selective regimes did not infer significant signal of either relaxed selection or episodic diversifying selection inCorallorhizabut did so for relaxed selection in the late-stage full mycoheterotrophic orchidsEpipogium aphyllumandGastrodia elata. Additionally, nucleotide substitutions that most likely impact the function ofWHY1, such as nonsense mutations, were only observed in late-stage mycoheterotrophs. We propose that our findings suggest that splicing and expression changes may precede the selective shifts we inferred for late-stage mycoheterotrophic species, which therefore does not support a primary role forWHY1in the transition to mycoheterotrophy in the Orchidaceae. Taken together, this study provides the most comprehensive view ofWHY1evolution across the angiosperms to date.