We present the 1.06 Gb sequenced genome of Gastrodia elata, an obligate mycoheterotrophic plant, which contains 18,969 protein-coding genes. Many genes conserved in other plant species have been deleted from the G. elata genome, including most of those for photosynthesis. Additional evidence of the influence of genome plasticity in the adaptation of this mycoheterotrophic lifestyle is evident in the large number of gene families that are expanded in G. elata, including glycoside hydrolases and urease that likely facilitate the digestion of hyphae are expanded, as are genes associated with strigolactone signaling, and ATPases that may contribute to the atypical energy metabolism. We also find that the plastid genome of G. elata is markedly smaller than that of green plant species while its mitochondrial genome is one of the largest observed to date. Our report establishes a foundation for studying adaptation to a mycoheterotrophic lifestyle.

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Some expressions and notations related to Equations 1 and 2 were presented incorrectly. The correct text and equations are below.The coefficients (β) in Cox's regression model are estimated by maximizing the partial likelihood function subject to a constraint on the L1-norm of the coefficients. The lasso estimator (β ) maximizes the objective function given below:Here l(β) is the log partial likelihood in the Cox model; for the exact form of this function, see ref. 41. The tuning parameter, λ in Equation 1, was chosen by 10-fold cross-validation. For the implementation, we used the R package "glmnet" (39).PROVAR was defined for each of the 222 TCGA samples as the sum of the estimated coefficients multiplied by protein expression levels, as shown below. Here i represents patients (i = 1,...,222), j represents proteins with nonzero coefficients (j = 1, ..., m), β j is the lasso coefficient of the jth protein marker, and X ij is the expression level of the jth protein for the ith patient. (Equation 2)The JCI regrets the error.

The plastid genome (plastome) of heterotrophic plants like mycoheterotrophs and parasites shows massive gene losses in consequence to the relaxation of functional constraints on photosynthesis. To understand the patterns of this convergent plastome reduction syndrome in heterotrophic plants, we studied 12 closely related orchids of three different lifeforms from the tribe Neottieae (Orchidaceae). We employ a comparative genomics approach to examine structural and selectional changes in plastomes within Neottieae. Both leafy and leafless heterotrophic species have functionally reduced plastid genome. Our analyses show that genes for the NAD(P)H dehydrogenase complex, the photosystems, and the RNA polymerase have been lost functionally multiple times independently. The physical reduction proceeds in a highly lineage-specific manner, accompanied by structural reconfigurations such as inversions or modifications of the large inverted repeats. Despite significant but minor selectional changes, all retained genes continue to evolve under purifying selection. All leafless Neottia species, including both visibly green and nongreen members, are fully mycoheterotrophic, likely evolved from leafy and partially mycoheterotrophic species. The plastomes of Neottieae span many stages of plastome degradation, including the longest plastome of a mycoheterotroph, providing invaluable insights into the mechanisms of plastome evolution along the transition from autotrophy to full mycoheterotrophy.