Browse Articles

Article|01 Feb 2023|OPEN
Pan-genome and transcriptome analyses provide insights into genomic variation and differential gene expression profiles related to disease resistance and fatty acid biosynthesis in eastern black walnut (Juglans nigra
Huijuan Zhou1,2,3 ,† , Feng Yan2 ,† , Fan Hao1 ,† , Hang Ye2 , Ming Yue2,3 , Keith Woeste4 , Peng Zhao2 , , Shuoxin Zhang,1 ,
1College of Forestry, Northwest A&F University, Yangling, Shaanxi 712100, China
2Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi’an, Shaanxi 710069, China
3Xi’an Botanical Garden of Shaanxi Province, Xi’an, Shaanxi 710061, China
4USDA Forest Service Hardwood Tree Improvement and Regeneration Center (HTIRC), Department of Forestry and Natural Resources, Purdue University, 715 West State Street, West Lafayette, Indiana, 47907, USA
*Corresponding author. E-mail: pengzhao@nwu.edu.cn,sxzhang@nwsuaf.edu.cn
Huijuan Zhou,Feng Yan,Fan Hao contributed equally to the study.

Horticulture Research 10,
Article number: uhad015 (2023)
doi: https://doi.org/10.1093/hr/uhad015
Views: 165

Received: 01 Nov 2022
Accepted: 27 Jan 2023
Published online: 01 Feb 2023

Abstract

Walnut (Juglans) species are used as nut crops worldwide. Eastern black walnut (EBW, Juglans nigra), a diploid, horticultural important woody species is native to much of eastern North America. Although it is highly valued for its wood and nut, there are few resources for understanding EBW genetics. Here, we present a high-quality genome assembly of J. nigra based on Illumina, Pacbio, and Hi-C technologies. The genome size was 540.8 Mb, with a scaffold N50 size of 35.1 Mb, and 99.0% of the assembly was anchored to 16 chromosomes. Using this genome as a reference, the resequencing of 74 accessions revealed the effective population size of J. nigra declined during the glacial maximum. A single whole-genome duplication event was identified in the J. nigra genome. Large syntenic blocks among J. nigraJuglans regia, and Juglans microcarpa predominated, but inversions of more than 600 kb were identified. By comparing the EBW genome with those of J. regia and J. microcarpa, we detected InDel sizes of 34.9 Mb in J. regia and 18.3 Mb in J. microcarpa, respectively. Transcriptomic analysis of differentially expressed genes identified five presumed NBS-LRR (NUCLEOTIDE BINDING SITE-LEUCINE-RICH REPEAT) genes were upregulated during the development of walnut husks and shells compared to developing embryos. We also identified candidate genes with essential roles in seed oil synthesis, including FAD (FATTY ACID DESATURASE) and OLE (OLEOSIN). Our work advances the understanding of fatty acid bioaccumulation and disease resistance in nut crops, and also provides an essential resource for conducting genomics-enabled breeding in walnut.