Journal Article

Genome of Crucihimalaya himalaica, a close relative of Arabidopsis, shows ecological adaptation to high altitude

Liu, Yixuan, Huang, Jinling, Guan, Yanlong, Al-Shehbaz, Ihsan A., Van de Peer, Yves, Van Montagu, Marc, Yue, Jipei, Liu, Tianmeng, Wang, Qia, Qiong, La, Zhang, Ticao, Sun, Hang, Qiao, Qin, De, Ji, Novikova, Polina Yu, Ming, Shengping

2019

Overview

Crucihimalaya himalaica, a close relative of Arabidopsis and Capsella, grows on the Qinghai–Tibet Plateau (QTP) about 4,000 m above sea level and represents an attractive model system for studying speciation and ecological adaptation in extreme environments. We assembled a draft genome sequence of 234.72 Mb encoding 27,019 genes and investigated its origin and adaptive evolutionary mechanisms. Phylogenomic analyses based on 4,586 single-copy genes revealed that C. himalaica is most closely related to Capsella (estimated divergence 8.8 to 12.2 Mya), whereas both species form a sister clade to Arabidopsis thaliana and Arabidopsis lyrata, from which they diverged between 12.7 and 17.2 Mya. LTR retrotransposons in C. himalaica proliferated shortly after the dramatic uplift and climatic change of the Himalayas from the Late Pliocene to Pleistocene. Compared with closely related species, C. himalaica showed significant contraction and pseudogenization in gene families associated with disease resistance and also significant expansion in gene families associated with ubiquitin-mediated proteolysis and DNA repair. We identified hundreds of genes involved in DNA repair, ubiquitin-mediated proteolysis, and reproductive processes with signs of positive selection. Gene families showing dramatic changes in size and genes showing signs of positive selection are likely candidates for C. himalaica’s adaptation to intense radiation, low temperature, and pathogen-depauperate environments in the QTP. Loss of function at the S-locus, the reason for the transition to selff-ertilization of C. himalaica, might have enabled its QTP occupation. Overall, the genome sequence of C. himalaica provides insights into the mechanisms of plant adaptation to extreme environments.

• Publisher: National Academy of Sciences
• Subject: Acclimatization - genetics / Acclimatization - physiology / Adaptation / Adaptation, Physiological - genetics / Adaptation, Physiological - physiology / Altitude / Arabidopsis / Arabidopsis - genetics / Arabidopsis - physiology / Biological evolution / Biological Sciences / Brassicaceae - genetics / Brassicaceae - physiology / Capsella / Capsella - genetics / Capsella - physiology / Climate Change / Crucihimalaya himalaica / Deoxyribonucleic acid / Disease resistance / Disease Resistance - genetics / Divergence / DNA / DNA repair / DNA Repair - genetics / Ecological adaptation / Ecological monitoring / Extreme Environments / Fertilization / Gene Dosage / Gene families / Genes / Genes, Plant - genetics / Genes, Plant - physiology / Genomes / High altitude / Low temperature / Nuclear Proteins - genetics / Nucleotide sequence / Phylogeny / Plant Biology / Plant Proteins - genetics / Pleistocene / Pliocene / PNAS Plus / Positive selection / Proteolysis / Repair / Sea level / Selection, Genetic / Self-fertilization / Self-Fertilization - genetics / Sequence Alignment / Speciation / Tibet / Ubiquitin / Uplift / Whole Genome Sequencing