Novel assembly strategy cracks open the mysteries of walnut genome evolution

Diversity of Chemical Structures and Biosynthesis of Polyphenols in Nut-Bearing Species

Nuts, such as peanut, almond, and chestnut, are valuable food crops for humans being important sources of fatty acids, vitamins, minerals, and polyphenols. Polyphenols, such as flavonoids, stilbenoids, and hydroxycinnamates, represent a group of plant-specialized (secondary) metabolites which are characterized as health-beneficial antioxidants within the human diet as well as physiological stress protectants within the plant. In food chemistry research, a multitude of polyphenols contained in culinary nuts have been studied leading to the identification of their chemical properties and bioactivities. Although functional elucidation of the biosynthetic genes of polyphenols in nut species is crucially important for crop improvement in the creation of higher-quality nuts and stress-tolerant cultivars, the chemical diversity of nut polyphenols and the key biosynthetic genes responsible for their production are still largely uncharacterized. However, current technical advances in whole-genome sequencing have facilitated that nut plant species became model plants for omics-based approaches. Here, we review the chemical diversity of seed polyphenols in majorly consumed nut species coupled to insights into their biological activities. Furthermore, we present an example of the annotation of key genes involved in polyphenolic biosynthesis in peanut using comparative genomics as a case study outlining how we are approaching omics-based approaches of the nut plant species.

Portal of Juglandaceae: A comprehensive platform for Juglandaceae study

Juglandaceae species are plants of great economic value and have been cultivated, domesticated, and utilized by human society for a long time. Their edible, nutrient-rich nuts and tough, durable wood have attracted the attention of botanists and breeders. With the advent of the genomics era, genome sequencing of the Juglandaceae family has been greatly accelerated, and a large amount of data has been generated. In this paper, we introduce the Portal of Juglandaceae (PJU), a tool to bring all these data together. The PJU contains genomes, gene-coding sequences, protein sequences, various types of annotation information, expression data, and miRNA data, which are configured with BLAST, JBrowse, and our self-developed synteny analysis tool. The PJU has a user-friendly and straightforward interface that performs a variety of query tasks with a few simple operations. In the future, we hope that the PJU will serve as a hub for the study of the Juglandaceae family.

Distinguishing Sichuan Walnut Cultivars and Examining Their Relationships with Juglans regia and J. sigillata by FISH, Early-Fruiting Gene Analysis, and SSR Analysis

Walnuts are economically important tree species in Sichuan Province (China) that provide heathy nuts. Fluorescence in situ hybridization (FISH) and analyses of an early-fruiting gene fragment and simple sequence repeats (SSRs) were used to distinguish Sichuan walnut cultivars and examine their relationships with Juglans regia L. and Juglans sigillata Dode. Thirty-four small chromosomes were counted in four Sichuan walnut cultivars. In the four cultivars, 5S rDNA was located in the proximal regions of two chromosomes (5 and 6), while (AG₃T₃)₃ was located at both ends of each chromosome. The existence of the signal at both chromosome ends ensured accurate chromosome counts. 5S rDNA and (AG₃T₃)₃ were not effective in identifying Sichuan walnut cultivars. Evolutionary analysis involving 32 early-fruiting nucleotide sequences from Sichuan walnut materials were performed with the maximum likelihood method. There were a total of 602 positions. All positions with gaps and missing data were eliminated, resulting in a final dataset of 562 positions. The ML tree with the highest log likelihood (-1607.82) revealed two obvious groups: one including materials of J. regia, which fruits 1 year after grafting, and another including materials of J. sigillata, which fruits >3 years after grafting. The early-fruiting gene fragment divided 22 walnut materials (10 walnut cultivars and 12 walnut accessions) into two groups, indicating that it was somewhat effective for distinguishing Sichuan walnut cultivars. Furthermore, 22 SSR loci were revealed to identify nine walnut cultivars. Eight cultivars were exclusively discerned by one SSR locus each: Chuanzao 1 [CUJRB307 (116) or CUJRA206a (182)], Chuanzao 2 [JSI-73 (154)], Shuangzao [CUJRB103a (123), CUJRB218 (144), JSI-71 (146), or CUJRA206a (176)], Shimianju [ZMZ11 (138)], Meigupao [CUJRB218 (149), CUJRB103a (151), or CUJRA206a (190)], Muzhilinhe [CUJRB220 (136), ZMZ11 (147), CUJRC310 (156), or JSI-73 (166)], Maerkang [CUJRA124 (154), CUJRB218 (159), or CUJRA123 (182)], Yanyuanzao [CUJRA124 (150) or CUJRA206a (192)]. The Shuling cultivar was identified by the combination of ZMZ11 (148) and other SSR loci, which distinguished and excluded the Chuanzao 1 and Yanyuanzao cultivars. Our results will guide the identification and breeding of Sichuan walnut cultivars.

Genome sequences of horticultural plants: past, present, and future

Horticultural plants play various and critical roles for humans by providing fruits, vegetables, materials for beverages, and herbal medicines and by acting as ornamentals. They have also shaped human art, culture, and environments and thereby have influenced the lifestyles of humans. With the advent of sequencing technologies, there has been a dramatic increase in the number of sequenced genomes of horticultural plant species in the past decade. The genomes of horticultural plants are highly diverse and complex, often with a high degree of heterozygosity and a high ploidy due to their long and complex history of evolution and domestication. Here we summarize the advances in the genome sequencing of horticultural plants, the reconstruction of pan-genomes, and the development of horticultural genome databases. We also discuss past, present, and future studies related to genome sequencing, data storage, data quality, data sharing, and data visualization to provide practical guidance for genomic studies of horticultural plants. Finally, we propose a horticultural plant genome project as well as the roadmap and technical details toward three goals of the project.