1Core Botanical Gardens/Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, China 2CAS Key Laboratory of Plant Germplasm Enhancement and Specialty Agriculture, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, China 3Sino-Africa Joint Research Center, Chinese Academy of Sciences, Wuhan 430074, China 4CAS Key Laboratory of Plant Resources, Institute of Botany, Chinese Academy of Science, Beijing 100093, China 5University of Chinese Academy of Sciences, Beijing 100049, China 6Key Laboratory of Southern Subtropical Plant Diversity, Fairy Lake Botanical Garden, Shenzhen & Chinese Academy of Science, Shenzhen 518004, China 7State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Science, Beijing 100093, China 8Center for Genomics and Biotechnology, Haixia Institute of Science and Technology, Fujian Agriculture and Forestry University, Fuzhou 350002, China 9Department of Horticultural Science, North Carolina State University, Raleigh, NC 27695, USA 10Department of Botany, Jomo Kenyatta University of Agriculture and Technology, 62000-00200, Nairobi, Kenya 11Department of Botany, National Museum of Natural History, Smithsonian Institution, Washington DC 20013-7012, USA *Corresponding author. E-mail: zl249@ibcas.ac.cn,wenj@si.edu,qfwang@wbgcas.cn †Haiping Xin and Yi Wang,Qingyun Li,Tao Wan contributed equally to the study.
Cissus is the largest genus in Vitaceae and is mainly distributed in the tropics and subtropics. Crassulacean acid metabolism (CAM), a photosynthetic adaptation to the occurrence of succulent leaves or stems, indicates that convergent evolution occurred in response to drought stress during species radiation. Here we provide the chromosomal level assembly of Cissus rotundifolia (an endemic species in Eastern Africa) and a genome-wide comparison with grape to understand genome divergence within an ancient eudicot family. Extensive transcriptome data were produced to illustrate the genetics underpinning C. rotundifolia’s ecological adaption to seasonal aridity. The modern karyotype and smaller genome of C. rotundifolia (n = 12, 350.69 Mb/1C), which lack further whole-genome duplication, were mainly derived from gross chromosomal rearrangements such as fusions and segmental duplications, and were sculpted by a very recent burst of retrotransposon activity. Bias in local gene amplification contributed to its remarkable functional divergence from grape, and the specific proliferated genes associated with abiotic and biotic responses (e.g. HSP-20, NBS-LRR) enabled C. rotundifolia to survive in a hostile environment. Reorganization of existing enzymes of CAM characterized as diurnal expression patterns of relevant genes further confer the ability to thrive in dry savannas.
, Jun Wen11 ,
