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Genome-wide association studies (GWAS) have been widely used to dissect the complex biosynthetic processes of plant metabolome. Most studies have used single-locus GWAS approaches, such as mixed linear model (MLM), and little is known about more efficient algorithms to implement multi-locus GWAS. Here, we report a comprehensive GWAS of 20 free amino acid (FAA) levels in kernels of bread wheat (Triticumaestivum L.) based on 14,646 SNPs by six multi-locus models (FASTmrEMMA, FASTmrMLM, ISISEM-BLASSO, mrMLM, pKWmEB, and pLARmEB). Our results showed that 328 significant quantitative trait nucleotides (QTNs) were identified in total (38, 8, 92, 45, 117, and 28, respectively, for the above six models). Among them, 66 were repeatedly detected by more than two models, and 155 QTNs appeared only in one model, indicating the reliability and complementarity of these models. We also found that the number of significant QTNs for different FAAs varied from 8 to 41, which revealed the complexity of the genetic regulation of metabolism, and further demonstrated the necessity of the multi-locus GWAS. Around these significant QTNs, 15 candidate genes were found to be involved in FAA biosynthesis, and one candidate gene (TraesCS1D01G052500, annotated as tryptophan decarboxylase) was functionally identified to influence the content of tryptamine in vitro. Our study demonstrated the power and efficiency of multi-locus GWAS models in crop metabolome research and provided new insights into understanding FAA biosynthesis in wheat.

Abstract: Larval rearing of Asian seabass is dependent on live food, similar to several other carnivorous fish species. The present study aimed to find suitable predigested protein sources for use in Asian seabass larval diets in order to reduce dependency on live feed. Fish muscle, squid mantle and soybean meal were hydrolyzed by Alcalase (alkaline enzyme), pepsin (acidic enzyme), and the combination of both enzymes producing a total of 9 protein hydrolysate (PH) products. The soybean meal was found least favorable for the larvae and omitted from the in vivo investigation. Fish muscle and squid mantle hydrolysate products were selected based on in vitro digestibility to replace fishmeal protein at 25% and 50% in isonitrogenous (50% protein) and isolipidic (20% lipid) diets. A diet with 0% PH was used as a control diet, and two other diets, one with minced mackerel muscle supplying protein, and a commercial diet were included as reference diets. The experimental diets were fed to larvae four times daily for 30days from 17days post hatch. Survival rate and growth performance were measured and enzyme activity and gene expression of stomach, pancreatic and brush border enzymes were determined. Larvae accepted all PH diets and the control diet well but did not accept the two reference diets which caused 100% mortality in the third week of the trial. In general, 25% PH inclusion increased larval growth compared to the 0% control group and increased specific activity of pancreatic and brush border enzymes. At 50% inclusion level, negative effects on growth performance and survival rate were observed. High levels of small peptides in the PH might have influenced digestive enzyme capacity as reflected in induced chymotrypsin activity but reduced mRNA level and specific enzyme activity of the brush border enzyme, leucine aminopeptidase. In conclusion, incorporation of 25% PH from either fish muscle or squid mantle treated with the Alcalase-pepsin enzyme combination improved digestive capacity and growth performance of the larvae with acceptable survival rate. [Copyright &y& Elsevier]

The objective of this study was to explore the effect of fungi on volatiles in sour meat. Here, we investigated the microbial community composition in meat after 80 days of fermentation and concluded that Lactobacillus , Debaryomyces , Pichia , and Wickerhamomyces were the dominant microorganisms in the sour meat. The inhibition of fungi in the sour meat by natamycin reduced the number of volatiles from 74 to 60. Esters, alcohols, aldehydes, ketones, and hydrocarbons were significantly lower in antibiotic-treated group (Group B) than in control group (Group A). The relative odor activity value (ROAV) showed that decanal, 1-octen-3-ol, ethyl heptanoate, and nonanal contributed to the flavor of the sour meat in both groups, and their relative content and contribution were significantly higher in Group A than in Group B, indicating that natamycin attenuated the contribution of these substances to the flavor of the sour meat. Finally, multivariate data analysis was performed to obtain 21 volatiles (variables important in the projection [VIP] > 1) that caused differences in the meat flavor between the two groups. The study provides a theoretical basis for future research on mechanisms of flavor formation in fermented products from a microbial perspective. • High-throughput sequencing technology to analyze microbial diversity in sour meat. • SPME-GC-MS combined with ROAV screened for 20 key volatile compounds. • 21 differential volatile flavor compounds obtained based on VIP >1.0 • Fungi play an important role in the formation of volatiles in sour meat. [ABSTRACT FROM AUTHOR]

Abstract: A sub-acute experiment that tested carbon and nitrogen metabolisms and the plant's antioxidant defence system was used to investigate the effects of nitrate enrichment and salinity reduction on the tropical seagrass Thalassia hemprichii that had previously been grown in low light conditions. Shading significantly reduced leaf growth rate, nitrate reductase activity and non-structural carbohydrate (NSC) content in both aboveground and belowground tissues, but enhanced superoxide dismutase and guaiacol peroxidase (POD) activities and free amino acids in aboveground tissue. After shade removal, salinity reduction with pre-shading decreased minimum fluorescence and maximum fluorescence under all nitrate conditions. Pre-shading aggravated the negative effect of nitrate enrichment and salinity reduction on leaf growth rate. Nitrate enrichment led to a greater reduction in NSC in aboveground tissues of pre-shading plants compared to the control. Furthermore, salinity reduction with pre-shading even induced effective NSC translocation from belowground to aboveground tissues. Nitrate enrichment and salinity reduction both increased POD activity in T. hemprichii grown previously in low light. Therefore, pre-shading increases the vulnerability of T. hemprichii to eutrophication and hyposalinity, which must be considered when predicting future responses and effective management of seagrass resources. [Copyright &y& Elsevier]

Abstract: We carried out a cultivation experiment using an artificial red mutant of Porphyra yezoensis isolated by heavy-ion beam mutagenesis to evaluate whether the red mutant has potential as a new cultivar. The blade length of the red mutant was shorter than that of a wild-type HG-511 at the first harvest. However, the results of the present study suggest that the red mutant tends to increase the contents of phycoerythrin, total free amino acid (FAA), alanine and taurine in comparison with the wild type. These tendencies toward the FAA contents were strongly supported by the laboratory culture experiment. From these superior characteristics of pigment and FAA contents, the red mutant IBY-R1 may become a new cultivar in nori cultivation, although it is possible that the mutant harvest will be lower than that of other cultivars. [Copyright &y& Elsevier]