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Article|13 Jun 2023|OPEN
A high-quality Bougainvillea genome provides new insights into evolutionary history and pigment biosynthetic pathways in the Caryophyllales 
Lan Lan1,2,3 ,† , Huiqi Zhao4,5 ,† , Suxia Xu6 , Shenglong Kan3 , Xiaoni Zhang1,3 , Weichao Liu3,7 and Xuezhu Liao1,3 , Luke R. Tembrock8 , Yonglin Ren2 , Wayne Reeve2 , Jun Yang4,5 , , Zhiqiang Wu,1,3 ,
1Shenzhen Branch, Guangdong Laboratory of Lingnan Modern Agriculture, Genome Analysis Laboratory of the Ministry of Agriculture and Rural Affairs, Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen, 518120, China
2School of Medical, Molecularand Forensic Sciences, Murdoch University, 6150, Western Australia, 90 South Street, Murdoch, Australia
3Kunpeng Institute of Modern Agriculture at Foshan, Shenzhen Branch, Guangdong Laboratory of Lingnan Modern Agriculture, Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen 518124, China
4Sanya Institute, Hainan Academy of Agricultural Sciences, Sanya, 572025, China
5Institute of Tropical Horticulture Research, Hainan Academy of Agricultural Sciences, Haikou, 571100, China
6Fujian Key Laboratory of Subtropical Plant Physiology & Biochemistry, Fujian Institute of Subtropical Botany, Xiamen, 361006, China
7Key Laboratory of Horticultural Plant Biology, College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan, 430070, China
8Department of Agricultural Biology, Colorado State University, Fort Collins, CO, 80523, USA
*Corresponding author. E-mail: juny83@126.com,wuzhiqiang@caas.cn
†Both authors contributed equally to the study.

Horticulture Research 10,
Article number: uhad124 (2023)
doi: https://doi.org/10.1093/hr/uhad124
Views: 183

Received: 10 Mar 2023
Accepted: 05 Jun 2023
Published online: 13 Jun 2023

Abstract

Bougainvillea is a perennial ornamental shrub that is highly regarded in ornamental horticulture around the world. However, the absence of genome data limits our understanding of the pathways involved in bract coloration and breeding. Here, we report a chromosome-level assembly of the giga-genome of Bougainvillea × buttiana ‘Mrs Butt’, a cultivar thought to be the origin of many other Bougainvillea cultivars. The assembled genome is ~5 Gb with a scaffold N50 of 151 756 278 bp and contains 86 572 genes which have undergone recent whole-genome duplication. We confirmed that multiple rounds of whole-genome multiplication have occurred in the evolutionary history of the Caryophyllales, reconstructed the relationship in the Caryophyllales at whole genome level, and found discordance between species and gene trees as the result of complex introgression events. We investigated betalain and anthocyanin biosynthetic pathways and found instances of independent evolutionary innovations in the nine different Caryophyllales species. To explore the potential formation mechanism of diverse bract colors in Bougainvillea, we analyzed the genes involved in betalain and anthocyanin biosynthesis and found extremely low expression of ANS and DFR genes in all cultivars, which may limit anthocyanin biosynthesis. Our findings indicate that the expression pattern of the betalain biosynthetic pathway did not directly correlate with bract color, and a higher expression level in the betalain biosynthetic pathway is required for colored bracts. This improved understanding of the correlation between gene expression and bract color allows plant breeding outcomes to be predicted with greater certainty.