Chromosome-level assembly, genetic and physical mapping of Phalaenopsis aphrodite genome provides new insights into species adaptation and resources for orchid breeding
Journal
Plant Biotechnology Journal
Journal Volume
16
Pages
2027-2041
Date Issued
2018
Author(s)
Ya-Ting Chao
Wan-Chieh Chen
Chun-Yi Chen
Hsiu-Yin Ho
Chih-Hsin Yeh
Yi-Tzu Kuo
Chun-Lin Su
Shao-Hua Yen
Hao-Yen Hsueh
Jen-Hau Yeh
Hui-Lan Hsu
Yi-Hui Tsai
Tzu-Yen Kuo
Song-Bin Chang
Abstract
The Orchidaceae is a diverse and ecologically important plant family. Approximately 69% of all orchid species are epiphytes, which provide diverse microhabitats for many small animals and fungi in the canopy of tropical rainforests. Moreover, many orchids are of economic importance as food flavourings or ornamental plants. Phalaenopsis aphrodite, an epiphytic orchid, is a major breeding parent of many commercial orchid hybrids. We provide a high-quality chromosomescale assembly of the P. aphrodite genome. The total length of all scaffolds is 1025.1 Mb, with N50 scaffold size of 19.7 Mb. A total of 28 902 protein-coding genes were identified. We constructed an orchid genetic linkage map, and then anchored and ordered the genomic scaffolds along the linkage groups. We also established a high-resolution pachytene karyotype of
P. aphrodite and completed the assignment of linkage groups to the 19 chromosomes using fluorescence in situ hybridization. We identified an expansion in the epiphytic orchid lineage of FRS5-like subclade associated with adaptations to the life in the canopy. Phylogenetic analysis further provides new insights into the orchid lineage-specific duplications of MADS-box genes,
which might have contributed to the variation in labellum and pollinium morphology and its accessory structure. To our knowledge, this is the first orchid genome to be integrated with a SNP-based genetic linkage map and validated by physical mapping. The genome and genetic map not only offer unprecedented resources for increasing breeding efficiency in horticultural
orchids but also provide an important foundation for future studies in adaptation genomics of epiphytes.
Subjects
plant genome
orchid
de novo assembly
genetic mapping
restriction site-associated DNA sequencing
fluorescence in situ hybridization
Type
journal article