INTRODUCTION: Nicotinamide mononucleotide (NMN) has important biological activities such as anti-cancer, anti-aging and improving crop stress resistance, and its importance as a nutritional health product has been established. However, the content of NMN in plants is low, and the metabolic pathway of NMN degradation is poorly understood. It has been reported that 5'-nucleotidases can catalyze the dephosphorylation of NMN in saccharomyces cerevisiae. At present, 5'-nucleotidases have been isolated in plants, but whether they can catalyze the degradation of NMN remains unclear. Edible kale has high nutritional value. It is important to analyze the metabolic pathway of NMN in kale and increase the content of NMN by blocking the degradation pathway. 

RATIONALE: The degradation of NMN in plants is closely related to the NAD+ remediation synthesis (pyridine nucleotide cycle) pathway. Compared with bacteria and mammals, studies on the synthetic pathway of NAD+ remediation in plants mainly use isotope tracer method, lack specific gene and function analysis, and only a few related studies have been reported in plants. Eight 5'-nucleotidase genes were cloned from Collard cabbage, heterologous expression of them was performed by Escherichia coli expression system, and the catalytic properties of 5'-nucleotidase were investigated by enzymological means in vitro. 

RESULTS: In this study, ten 5'-nucleotidase genes were retrieved from the kale genome. Based on these sequences, eight 5'-nucleotidase candidate genes were successfully cloned from Brassica oleracea var. acephala, which laid a foundation for further revealing the degradation pathway of NMN. Phylogenetic analysis revealed that 5'-nucleotidase is conserved in plants, suggesting that it may play an important role in plant nucleotide metabolism. The catalytic properties of 5'-nucleotides in kale were investigated by using the expression system of Escherichia coli. In vitro enzymatic experiments showed that 5'-nucleotides can catalyze purine, pyrimidine and pyridine nucleotides, and have a wide range of substrate adaptability. Specifically, BolN2, BolN5-X1 and BolN6 can catalyze the dephosphorylation of NMN to the generation of NR, which proves that 5'-nucleotidase can catalyze the degradation of NMN in plants. In addition, BolN2, BolN5 and BolN6 can catalyze the hydrolysis of pyridine nucleotides NaMN, purine and pyrimidine nucleotides (including AMP, GMP, CMP and UMP). However, BolN7 and BolN8 have only weak catalytic activity against GMP. 

CONCLUSION: In conclusion, the 5'-nucleotidase gene from the HAD and SurE families of Collard Brassica oleracea var. acephala was cloned and phylogenetic analysis showed that it was conserved in plants. By constructing prokaryotic expression vector, 5'-nucleotidase was expressed and purified in Escherichia coli. The results of enzymatic reaction in vitro showed that BolN2, BolN5-X1 and BolN6 could catalyze the degradation of NMN to produce NR. In addition, BolN2, BolN5 and BolN6 have catalytic effects on NaNM, purine and pyrimidine nucleotides. This study further enhanced our understanding of the NMN metabolic pathway in kale, and provided a theoretical basis for creating edible kale with high NMN content.

INTRODUCTION: Galactinol synthase (GolS) is a key enzyme in the biosynthetic pathway of raffinose family oligosaccharides (RFOs), providing the activated galactosyl group for the biosynthesis and accumulation of RFOs in plants. It plays an important role in plant responses to abiotic stresses. 

RATIONALE: Although the role of GolS in plant stress responses has been extensively studied, little is known about the molecular characteristics of the GolS gene family (LiGolS) in Lagerstroemia indica. This study aims to identify the members of the LiGolS gene family, analyze their physicochemical properties, gene structure, and expression patterns, and explore their potential functions in salt stress response. 

RESULTS: A total of 13 LiGolS gene family members were identified at the whole-genome level and were classified into three subfamilies based on phylogenetic relationships. These genes were unevenly distributed across 10 chromosomes. The isoelectric points of the 13 LiGolS proteins ranged from 4.75 to 9.45, with molecular weights varying from 37.69 to 46.12 kDa and amino acid counts ranging from 327 to 404. Subcellular localization prediction revealed that six proteins were localized to chloroplasts, one to mitochondria, five to the cytoplasm, and one to vacuoles. Additionally, the number of exons in the 13 gene members ranged from 0 to 4. Expression analysis under salt stress showed that all LiGolS genes were upregulated to varying degrees after salt treatment, suggesting their potential involvement in salt stress response in Lagerstroemia indica. 

CONCLUSION: This study systematically identified and characterized the LiGolS gene family members in Lagerstroemia indica for the first time, including their physicochemical properties, gene structure, and expression patterns. These results lay the foundation for further functional analysis of LiGolS genes and provide theoretical insights into their roles in stress responses.

INTRODUCTION: Genetic diversity is considered as a crucial aspect in assessment and conservation of rare and endangered species. Brachystachyum densiflorum is a species endemic to eastern China. In recent years, with rapid economic development, accelerated urbanization, and escalating pollutant emissions, the habitat of B. densiflorum has been continuously degraded, habitat fragmentation has intensified, and its populations have shown a tendency to decline. 

RATIONALE: Genetic diversity endows species with abundant genetic resources and plays a pivotal role in shaping their capacity to adapt to new environments. To elucidate the genetic diversity of B. densiflorum and evaluate the influence of climate change on its genetic variation, reduced-representation genome sequencing technology was employed to obtain single nucleiotide polymorphisms (SNPs), and subsequently population genetics and landscape genetics together with species distribution modelling were analyzed. 

RESULTS: Brachystachyum densiflorum had a moderate level of genetic diversity. Six populations were divided into two groups, and there was moderate differentiation (F_ST=0.102) and high gene flow (Nm=2.442) between them. Genotype-environment association analysis indicated that the two groups were diverged attributable to local adaptation to the climate. Temperature differentials and low-temperature regimes interacting together with precipitation gave rise to genetic variation of this species. In total, 544 adaptive loci were identified, which displayed significant correlations with temperature differentials, low-temperature factors (Bio2, Bio6, Bio11, and Bio7), and precipitation factors (Bio19). B. densiflorum migrated evidently northward from the Last Glacial Maximum to the current, with its distribution area increased by 89.5%. However, during the period from 2061 to 2080, the extent of the suitable area for this species will be contracted, and there will be partial degradation and fragmentation occurring in highly suitable areas within Anhui Province. 

CONCLUSION: Brachystachyum densiflorum showed a moderate level of genetic diversity and a moderate degree of genetic differentiation. Local adaptation drove the formation of the current genetic pattern of B. densiflorum, and temperature differences, low-temperature, and precipitation led to genetic variation. B. densiflorum has evidently migrated northward from the Last Glacial Maximum to the current with increase of distribution area. However, niche modelling indicated that during the period from 2061 to 2080, the suitable habitat area of B. densiflorum would be contracted, with partial degradation and fragmentation occurring in highly suitable areas within Anhui Province. These results have significant meanings for conservation and utilization of B. densiflorum.