Genomes of leafy and leafless Platanthera orchids illuminate the evolution of mycoheterotrophy
Li, Ming-He; Liu, Ke-Wei; Li, Zhen; Lu, Hsiang-Chia; Ye, Qin-Liang; Zhang, Diyang; Wang, Jie-Yu; Li, Yu-Feng; Zhong, Zhi-Ming; Liu, Xuedie; Yu, Xia; Liu, Ding-Kun; Tu, Xiong-De; Liu, Bin; Hao, Yang; Liao, Xing-Yu; Jiang, Yu-Ting; Sun, Wei-Hong; Chen, Jinliao; Chen, Yan-Qiong; Ai, Ye; Zhai, Jun-Wen; Wu, Sha-Sha; Zhou, Zhuang; Hsiao, Yu-Yun; Wu, Wan-Lin; Chen, You-Yi; Lin, Yu-Fu; Hsu, Jui-Ling; Li, Chia-Ying; Wang, Zhi-Wen; Zhao, Xiang; Zhong, Wen-Ying; Ma, Xiao-Kai; Ma, Liang; Huang, Jie; Chen, Gui-Zhen; Huang, Ming-Zhong; Huang, Laiqiang; Peng, Dong-Hui; Luo, Yi-Bo; Zou, Shuang-Quan; Chen, Shi-Pin; Lan, Siren; Tsai, Wen-Chieh; Van de Peer, Yves; Liu, Zhong-Jian
Date:
2022-05-21
Abstract:
To improve our understanding of the origin and evolution of mycoheterotrophic plants, we here present the chromosome-scale
genome assemblies of two sibling orchid species: partially mycoheterotrophic Platanthera zijinensis and holomycoheterotrophic
Platanthera guangdongensis. Comparative analysis shows that mycoheterotrophy is associated with increased substitution
rates and gene loss, and the deletion of most photoreceptor genes and auxin transporter genes might be linked to the unique
phenotypes of fully mycoheterotrophic orchids. Conversely, trehalase genes that catalyse the conversion of trehalose into glucose
have expanded in most sequenced orchids, in line with the fact that the germination of orchid non-endosperm seeds needs
carbohydrates from fungi during the protocorm stage. We further show that the mature plant of P. guangdongensis, different
from photosynthetic orchids, keeps expressing trehalase genes to hijack trehalose from fungi. Therefore, we propose that
mycoheterotrophy in mature orchids is a continuation of the protocorm stage by sustaining the expression of trehalase genes.
Our results shed light on the molecular mechanism underlying initial, partial and full mycoheterotrophy.
Description:
DATA AVAILABILITY : Genome sequences and whole-genome assemblies have been submitted to the NCBI database under BioProject PRJNA739531.