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PubMed2025

Analysis of genetic differences underlying chilling stress tolerance using whole genome Re-Sequencing in walnut (Juglans regia L.).

Walnut (Juglans regia L.) is prized worldwide for both its nutritional value and economic importance, yet it remains vulnerable to cold stress, with significant differences in tolerance among varieties. This study combined physiological analyses with whole-genome resequencing (WGS) to evaluate the cold stress responses of two varieties, ‘Qingxiang’ and ‘Liaoning No.8’. Under chilling stress (0 °C), we measured electrolyte leakage and antioxidant enzyme activity, applying both exogenous methyl jasmonate (MeJA) and the jasmonate inhibitor DIECA. Genomic variations were analyzed using WGS. Results showed that ‘Liaoning No.8’ exhibited superior cold tolerance. Application of MeJA reduced electrolyte leakage by 37% and MDA accumulation by 52% on average, whereas DIECA exacerbated stress-related damage. WGS achieved 16.24–16.26× coverage and identified 2.73–2.78 million SNPs, 378–382k InDels, 25–26k SVs, and 7.2–7.9k CNVs. Twenty genes containing sequence variants showed transcriptional responses under cold stress that were significantly correlated with mutation density (r = 0.62, P < 0.01). One gene, XM_018985465.2, which lacked SNPs in ‘Liaoning No.8’, was expressed 4.2 times more in this variety, suggesting cis-regulatory influence. These findings highlight the role of jasmonic acid signaling in enhancing cold tolerance in walnut and offer genomic insights into its underlying adaptive mechanisms.

Juglans↗

PubMed2026

Genome-Wide Identification and Bioinformatics Analysis of the FAD Gene Family in Walnut (Juglans regia L.).

Fatty acid desaturase (FAD) is a core catalytic enzyme in plants for the synthesis of unsaturated fatty acids, profoundly affecting plant growth, development, and adaptability to various environmental stresses. The walnut (Juglans regia L.) is an important woody oil tree species, and its kernel is rich in unsaturated fatty acids. Systematic identification of the walnut FAD gene family and analysis of its function are of great significance for revealing the molecular mechanisms underlying unsaturated fatty acid metabolism in the walnut. Based on walnut whole-genome data, this study used homology alignment and hidden Markov model search methods to identify the JrFAD gene family members. Subsequently, a variety of bioinformatics tools were used to systematically analyze their structural characteristics, evolutionary expansion mechanism, expression regulation, and function. A total of 21 JrFAD gene family members were identified and classified into five subfamilies. The family genes were unevenly distributed on nine chromosomes. WGD/segmental duplication was the main expansion method, and the duplicated gene pairs experienced strong purification selection. The family gene promoter sequence is rich in regulatory elements that respond to light, plant hormones, and various stresses. The expression pattern analysis showed that JrFAD3.1 and JrFAD2.3 showed high expression specifically during the rapid accumulation of walnut kernel oil. This study clarified the composition and evolutionary characteristics of the FAD gene family in the walnut, which provides useful information for in-depth analyses of its functional mechanism in the regulation of lipid metabolism, and also identified potential candidate gene resources for the genetic improvement of walnut varieties with high amounts of unsaturated fatty acids.

Juglans↗

PubMed2025

Integrated multi-omics analyses provide new insights into genomic variation landscape and regulatory network candidate genes associated with walnut endocarp.

Persian walnut (Juglans regia) is an economically important nut oil tree; the fruit has a hard endocarp/shell to protect seeds, thus playing a key role in its evolution, and the shell thickness is an important trait for walnut breeding. However, the genomic landscape and the gene regulatory networks associated with walnut shell development remain to be systematically elucidated. Here, we report a high-quality genome assembly of the walnut cultivar 'Xiangling' and construct a graphic structure pan-genome of eight Juglans species to reveal the genetic variations at the genome level. We re-sequence 285 accessions to characterize the genomic variation landscape. Through genome-wide association studies (GWAS), we identified 19 loci associated with more than 268 loci that underwent selection during walnut domestication and improvement. Multi-omics analyses, including transcriptomics, metabolomics, DNA methylation, and spatial transcriptomics across eleven developmental stages, revealed several candidate genes related to secondary cell biosynthesis and lignin accumulation. This integrated multi-omics approach revealed several candidate genes associated with secondary cell biosynthesis and lignin accumulation, such as UGP, MYB308, MYB83, NAC043, NAC073, CCoAOMT1, CCoAOMT7, CHS2, CESA7, LAC7, COBL4, and IRX12. Overexpression of JrUGP and JrMYB308 in Arabidopsis thaliana confirmed their roles in lignin biosynthesis and cell wall thickening. Consequently, our comprehensive multi-omics findings offer novel insights into walnut genetic variation and network regulation of endocarp development and shell thickness, which enable further genome-informed breeding strategies for walnut cultivar improvement.

Juglans↗

PubMed1991

An alternative approach for gene transfer in trees using wild-type Agrobacterium strains.

Micropropagated shoots of three forest tree species, poplar (Populus tremula x P. alba), wild cherry (Prunus avium L.) and walnut (Juglans nigra x J. regia), were inoculated each with six different wild-type Agrobacterium strains. Poplar and wild cherry developed tumors that grew hormone-independently, whereas on walnut, gall formation was weak. On poplar and wild cherry, tumors induced by nopaline strains developed spontaneously shoots that had a normal phenotype and did not carry oncogenic T-DNA. From these observations, we have established a co-inoculation method to transform plants, using poplar as an experimental model. The method is based on inoculation of stem internodes with an Agrobacterium suspension containing both an oncogenic strain that induces shoot differentiation and a disarmed strain that provides the suitable genes in a binary vector. We used the vector pBI121 carrying neo (kanamycin resistance) and uidA (beta-glucuronidase) genes to facilitate early selection and screening. Poplar plants derived from kanamycin-resistant shoots that did not carry oncogenic T-DNA, were shown to contain and to express neo and uidA genes. These results suggest that wild-type Agrobacterium strains that induce shoot formation directly from tumors can be used as a general tool for gene transfer, avoiding difficult regeneration procedures.

Culture Techniques↗

PubMedDate not supplied

Hunting poisons of the North Pacific Region.

The hunting poisons of the North Pacific region are discussed. The most important one used by the Ainu was based on Aconitum species (surku or suruku): on Hokkaido, to some extent A. japonicum Thumb. but probably mainly A. yezoense Nakai and A. sachalinense Fr. Schm.; on southern Sakhalin, perhaps A. fischeri Reichb., A. maximum Pall. ex DC., and/or A. sachalinense Fr. Schm.; and on the Kuril Islands, A. maximum Pall. ex DC. Poison from the Japanese stingray Dasyatis akajei (Müller et Henle) (aikor chiep) was also much used, alone or mixed with aconite, and was believed by some Ainu to be better than aconite. Adjuvants to these poisons were numerous and varied in each locality. Daphne kamtschatica Maxim. var. yezoensis (Maxim.) Ohwi (ketuhas) was used in hunting walrus. The use of Cynanchum caudatum (Miq.) Maxim. (penup) enabled birds to be caught. Juglans ailanthifolia Carr (nesko) was a fish poison. A critical evaluation of the accounts by Krasheninnikov, Steller, Harms, and others, indicates that the inhibitants of the Kamchatka Peninsula, the Kamchadal (Itelmen), hunted with a poison derived from Aconitum maximum Pall. ex DC. This same species was almost certainly used in the Aleutian Islands and the Kodiak Island region, principally for hunting whales. There is some evidence that the inhabitants of the far north-eastern part of Siberia and of the Alaskan coasts opposite may also have used poison in hunting. The chemistry and toxicology of the poisons are briefly considered.

Aconitum↗