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Platanthera guangdongensis genome
Genome Browser	Gene annotation	Metabolism pathway	Synteny	GeneOrder	miRNA	Regulation

Recently, chromosome-scale assembled genomes of two closely related orchids were published: one is a partially mycoheterotrophic orchid, Platanthera zijinensis, and the other is a fully mycoheterotrophic orchid, Platanthera guangdongensis. The two species are only found in one location in Zijin County, Guangdong Province, China, where they live alongside each other but in quite different habitats, with P. zijinensis mainly growing on light-abundant rocky hills and P. guangdongensis in the adjacent forest with a dense canopy. Also, P. zijinensis has leaves and a root system with tubercles, whereas P. guangdongensis has neither leaves nor roots, but has a tuber (vertical, underground stem), the organ to which the mycorrhizal fungi, critical to its holomycoheterotrophic lifestyle, are attached. Comparing the high-quality genomes of P. zijinensis and P. guangdongensis, together with other sequenced orchids, would hence enable us to study the evolution of initial, partial and full mycoheterotrophy in orchids. The two sequenced genomes of P. zijinensis and P. guangdongensis would also fill the gap between sequenced orchid genomes of photosynthetic orchids on one side and non-photosynthetic orchids on the other side, paving a way to identify possible genes related to mycoheterotrophy in Orchidaceae. The genes related to mycoheterotrophy at different developmental stages of both photosynthetic and non-photosynthetic orchids could also provide insights into the origin and evolution of mycoheterotrophy in Orchidaceae.

P. zijinensis and P. guangdongensis both have a karyotype of 2n = 2X = 42 chromosomes. To completely sequence the genomes, we generated a total of 441.16 Gb and 414.20 Gb data for P. zijinensis and P. guangdongensis, respectively, with multiple insert libraries using PacBio technologies. With k-mer analyses we estimated a genome size of 4.15 Gb for the P. zijinensis genome with a heterozygosity of 1.80% and a genome size of 4.27 Gb for the P. guangdongensis genome with a heterozygosity of 1.89%, thus indicating relatively high heterozygosity levels for both genomes. The total length of the genome assembly was 4.19 Gb with a contig N50 value of 1.77 Mb for the P. zijinensis genome and 4.20 Gb with a contig N50 value of 1.57 Mb for the P. guangdongensis genome.

Genomes of leafy and leafless Platanthera orchids illuminate the evolution of mycoheterotrophy. Li et al. 2022. Nature Plants.

Platanthera guangdongensis
Platanthera guangdongensis
Platanthera guangdongensis