Nitrogen Level Impacts the Dynamic Changes in Nitrogen Metabolism, and Carbohydrate and Anthocyanin Biosynthesis Improves the Kernel Nutritional Quality of Purple Waxy Maize.

Waxy corn is a special type of maize primarily consumed as a fresh vegetable by humans. Nitrogen (N) plays an essential role in regulating the growth progression, maturation, yield, and quality of waxy maize. A reasonable N application rate is vital for boosting the accumulation of both N and carbon (C) in the grains, thereby synergistically enhancing the grain quality. However, the impact of varying N levels on the dynamic changes in N metabolism, carbohydrate formation, and anthocyanin synthesis in purple waxy corn kernels, as well as the regulatory relationships among these processes, remains unclear. To explore the effects of varying N application rates on the N metabolism, carbohydrate formation, and anthocyanin synthesis in kernels during grain filling, a two-year field experiment was carried out using the purple waxy maize variety Jinnuo20 (JN20). This study examined the different N levels, specifically 0 (N0), 120 (N1), 240 (N2), and 360 (N3) kg N ha-1. The results of the analysis revealed that, for nearly all traits measured, the N application rate of N2 was the most suitable. Compared to the N0 treatment, the accumulation and content of anthocyanins, total nitrogen, soluble sugars, amylopectin, and C/N ratio in grains increased by an average of 35.62%, 11.49%, 12.84%, 23.74%, 13.00%, and 1.87% under N2 treatment over five filling stages within two years, respectively, while the harmful compound nitrite content only increased by an average of 30.2%. Correspondingly, the activities of related enzymes also significantly increased and were maintained under N2 treatment compared to N0 treatment. Regression and correlation analysis results revealed that the amount of anthocyanin accumulation was highly positively correlated with the activities of phenylalanine ammonia-lyase (PAL) and flavanone 3-hydroxylase (F3H), but negatively correlated with anthocyanidin synthase (ANS) and UDP-glycose: flavonoid-3-O-glycosyltransferase (UFGT) activity, nitrate reductase (NR), and glutamine synthetase (GS) showed significant positive correlations with the total nitrogen content and lysine content, and a significant negative correlation with nitrite, while soluble sugars were negatively with ADP-glucose pyrophosphorylase (AGPase) activity, and amylopectin content was positively correlated with the activities of soluble starch synthase (SSS), starch branching enzyme (SBE), and starch debranching enzyme (SDBE), respectively. Furthermore, there were positive or negative correlations among the detected traits. Hence, a reasonable N application rate improves purple waxy corn kernel nutritional quality by regulating N metabolism, as well as carbohydrate and anthocyanin biosynthesis.

Enrichment characteristics of microplastics in Antarctic benthic and pelagic fish and krill near the Antarctic Peninsula.

Global microplastic pollution has garnered widespread attention from researchers both domestically and internationally. However, compared to other regions worldwide, little is known about microplastic pollution in the marine ecosystems of the Antarctic region. This study investigated the abundance and characteristics of microplastics (MPs) in the gills and intestines of 15 species of Antarctic fish and Antarctic krill (Euphausia superba). The results indicate that the abundance of MPs in Antarctic fish and E. superba ranged from 0.625 to 2.0 items/individual and 0.17 to 0.27 items/individual, with mean abundances of 0.93 ± 0.96 items/individual and 0.23 ± 0.44 items/individual, respectively. Antarctic fish ingested significantly more MPs than E. superba. There was no significant difference in the abundance of MPs between the gills and intestines of Antarctic fish. However, the quantity of pellet-shaped MPs in the gills was significantly higher than in the intestines. The depth of fish habitat influenced the quantity and size of MPs in their bodies, with benthic fish ingesting significantly fewer MPs than pelagic fish. Pelagic fish ingested significantly more MPs sized 1-5 mm than benthic fish. Additionally, analysis of the characteristics of MPs revealed that fiber-shaped MPs were predominant in shape, with sizes generally smaller than 0.25 mm and 0.25-0.5 mm. The predominant colors of MPs were transparent, red, and black, while the main materials were polypropylene (PP), polystyrene (PS), polyamide (PA), and polyvinyl chloride (PVC). Compared to organisms from other regions, the levels of MPs in Antarctic fish and E. superba were relatively low. This study contributes to a better understanding of the extent of MP pollution in Antarctic fish and E. superba, aiding human efforts to mitigate its impact on the environment.

Nitrogen fertilizer application rate affects the dynamic metabolism of nitrogen and carbohydrates in kernels of waxy maize.

Introduction: Nitrogen (N) plays a pivotal role in the growth, development, and yield of maize. An optimal N application rate is crucial for enhancing N and carbohydrate (C) accumulation in waxy maize grains, which in turn synergistically improves grain weight. Methods: A 2-year field experiment was conducted to evaluate the impact of different N application rates on two waxy maize varieties, Jinnuo20 (JN20) and Jindannuo41 (JDN41), during various grain filling stages. The applied N rates were 0 (N0), 120 (N1), 240 (N2), and 360 (N3) kg N ha-1. Results: The study revealed that N application significantly influenced nitrogen accumulation, protein components (gliadin, albumin, globulin, and glutelin), carbohydrate contents (soluble sugars, amylose, and amylopectin), and activities of enzymes related to N and C metabolism in waxy maize grains. Notable varietal differences in these parameters were observed. In both varieties, the N2 treatment consistently resulted in the highest values for almost all measured traits compared to the other N treatments. Specifically, the N2 treatment yielded an average increase in grain dry matter of 21.78% for JN20 and 17.11% for JDN41 compared to N0. The application of N positively influenced the activities of enzymes involved in C and N metabolism, enhancing the biosynthesis of grain protein, amylose, and amylopectin while decreasing the accumulation of soluble sugars. This modulation of the C/N ratio in the grains directly contributed to an increase in grain dry weight. Conclusion: Collectively, our findings underscore the critical role of N in regulating kernel N and C metabolism, thereby influencing dry matter accumulation in waxy maize grains during the grain filling stage.

Case report: A novel mutation of the CAPN3 gene in a Chinese family with limb-girdle muscular dystrophy type 2A.

Limb-girdle muscular dystrophy type 2A (LGMD R1 Calpain 3-Related, LGMD2A/R1), an autosomal recessive disorder, is characterized by progressive muscle weakness with a prominent presentation in the proximal limb girdle muscles. LGMD2A/R1, which is caused by variants in calcium-activated neutral proteinase 3 (CAPN3), is the most common. The present study aimed at identifying the clinically significant variants in a Chinese family with LGMD2A/R1 and exploring the genotype-phenotype correlations. Clinical symptoms, laboratory findings, and physical examinations were obtained. Genomic DNA was extracted from the peripheral blood samples of this family. Whole-exome sequencing (WES) and Sanger sequencing were used to explore and validate the pathogenic genes. In this study, the proband and his sister, who had two identical mutations in the CAPN3 gene sequence, exhibited diverse clinical features, including disease onset and progression. The mutation c.2120 A>G (p. D707G) is pathogenic and has been reported in the Human Gene Mutation Database (HGMD) and the ClinVar database. c.1783-72 C>G may be a novel pathogenic mutation of LGMD2A/R1 based on the American College of Medical Genetics (ACMG) guidelines, which widens the gene variant pool in CAPN3 and improves diagnosis and genetic counseling.

[Dynamics of carbon and nitrogen balance during leaf senescence of maize seedlings induced by low nitrogen stress]. / 低氮诱导玉米幼苗叶片衰老过程中碳氮平衡的动态变化.

Timing of leaf senescence is important to ensure maize yield. In this study, we investigated the dynamics of carbon and nitrogen balance during leaf senescence in two maize inbred lines PH6WC and PH4CV under normal (4 mmol·L-1, CK) and low nitrogen (0.04 mmol·L-1, LN) treatments. Leaf phenotype, photosynthetic characteristics, nitrogen and sugar contents, and carbon to nitrogen ratio of the second and third leaves were analyzed after 2, 4, 6 and 8 days of cultivation. Results showed that leaf size, biomass, relative chlorophyll content, net photosynthetic rate, soluble sugar content, and starch content of the second and third leaves were decreased, while nitrogen production capacity was increased under low nitrogen treatment compared to the control, with the changes of the second leaf being earlier than that of the third leaf. For all the leaf traits, the variation scales of PH6WC were larger than that of PH4CV under low nitrogen stress, and only the C/N ratio in the seedling leaves was significantly increased. In addition, leaf senescence of PH4CV was slower than PH6WC due to its stronger ability in maintaining carbon and nitrogen balance. In conclusion, low nitrogen could induce leaf senescence of maize seedlings. High C/N ratio could promote leaf senescence. There are significant differences in carbon and nitrogen balance ability of seedling leaves between two maize genotypes under low nitrogen stress.

[Progress and application prospects of glutamine synthase in plants].

Nitrogen is one of the most important nutrient elements for plants and a major limiting factor in plant growth and crop productivity. Glutamine synthase (GS) is a key enzyme involved in the nitrogen assimilation and recycling in plants. So far, members of the glutamine synthase gene family have been characterized in many plants such as Arabidopsis, rice, wheat, and maize. Reports show that GS are involved in the growth and development of plants, in particular its role in seed production. However, the outcome has generally been inconsistent, which are probably derived from the transcriptional and post-translational regulation of GS genes. In this review, we outlined studies on GS gene classification, QTL mapping, the relationship between GS genes and plant growth with nitrogen and the distribution characters, the biological functions of GS genes, as well as expression control at different regulation levels. In addition, we summarized the application prospects of glutamine synthetase genes in enhancing plant growth and yield by improving the nitrogen use efficiency. The prospects were presented on the improvement of nitrogen utility efficiency in crops and plant nitrogen status diagnosis on the basis of glutamine synthase gene regulation.

Comparative proteomic analysis of embryos between a maize hybrid and its parental lines during early stages of seed germination.

In spite of commercial use of heterosis in agriculture, the molecular basis of heterosis is poorly understood. It was observed that maize hybrid Zong3/87-1 exhibited an earlier onset or heterosis in radicle emergence. To get insights into the underlying mechanism of heterosis in radicle emergence, differential proteomic analysis between hybrid and its parental lines was performed. In total, the number of differentially expressed protein spots between hybrid and its parental lines in dry and 24 h imbibed seed embryos were 134 and 191, respectively, among which 47.01% (63/134) and 34.55% (66/191) protein spots displayed nonadditively expressed pattern. Remarkably, 54.55% of nonadditively accumulated proteins in 24 h imbibed seed embryos displayed above or equal to the level of the higher parent patterns. Moreover, 155 differentially expressed protein spots were identified, which were grouped into eight functional classes, including transcription & translation, energy & metabolism, signal transduction, disease & defense, storage protein, transposable element, cell growth & division and unclassified proteins. In addition, one of the upregulated proteins in F1 hybrids was ZmACT2, a homolog of Arabidopsis thaliana ACT7 (AtACT7). Expressing ZmACT2 driven by the AtACT7 promoter partially complemented the low germination phenotype in the Atact7 mutant. These results indicated that hybridization between two parental lines can cause changes in the expression of a variety of proteins, and it is concluded that the altered pattern of gene expression at translational level in the hybrid may be responsible for the observed heterosis.