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Seaweed biomass has the potential to become an important raw material for bio-based production. The aim of this study was to screen the overall composition of several seaweed species on the Swedish west coast, including some scarcely studied species, to provide fundamentals for evaluation of biorefining potential and to benchmark with already potentially industrially relevant species and commercially important land-based biomasses. Twenty-two common seaweed species (green, red, brown) were collected and the carbohydrate, ash, protein, water and metal contents were measured. Carbohydrate content varied between 237 and 557 g kg−1 dry weight (dw), making it the largest constituent, on a dry weight basis, of most species in the study. Ash, which is considered unwanted in biorefining, ranged between 118 and 419 g kg−1 dw and was the largest constituent in several seaweeds, which were therefore considered unsuitable for biorefining. Protein content was most abundant in the red seaweeds but was generally low in all species (59–201 g kg−1 dw). High contents of several unwanted metals for processing or human consumption were found (e.g. aluminium, arsenic, copper, chromium and nickel), which need to be considered when utilizing seaweeds for certain applications. Potential targets for further biorefinery development mostly include species already known for their potential (Saccharina latissima, Laminaria digitata and Chondrus crispus) while some, such as Halidrys siliquosa and Dilsea carnosa, have not been previously noted. However, more detailed studies are required to explore biorefinery processes for these seaweeds, as well as how to potentially cultivate them.

Experimental studies have shown that human macronutrient regulation minimizes variation in absolute protein intake and consequently energy intake varies passively with dietary protein density ('protein leverage'). According to the 'protein leverage hypothesis' (PLH), protein leverage interacts with a reduction in dietary protein density to drive energy overconsumption and obesity. Worldwide increase in consumption of ultra-processed foods (UPF) has been hypothesized to be an important determinant of dietary protein dilution, and consequently an ecological driving force of energy overconsumption and the obesity pandemic. The present study examined the relationships between dietary contribution of UPF, dietary proportional protein content and the absolute intakes of protein and energy. National representative cross-sectional study. National Health and Nutrition Examination Survey 2009-2010. Participants (n 9042) aged ≥2 years with at least one day of 24 h dietary recall data. We found a strong inverse relationship between consumption of UPF and dietary protein density, with mean protein content dropping from 18·2 to 13·3 % between the lowest and highest quintiles of dietary contribution of UPF. Consistent with the PLH, increase in the dietary contribution of UPF (previously shown to be inversely associated with protein density) was also associated with a rise in total energy intake, while absolute protein intake remained relatively constant. The protein-diluting effect of UPF might be one mechanism accounting for their association with excess energy intake. Reducing UPF contribution in the US diet may be an effective way to increase its dietary protein concentration and prevent excessive energy intake.

Grain protein content (GPC) is one of the most important quality traits in wheat, defining the nutritional and end-use properties and rheological characteristics. Over the years, a number of breeding programs have been developed aimed to improving GPC, most of them having been prevented by the negative correlation with grain yield. To overcome this issue, a collection of durum wheat germplasm was evaluated for both GPC and grain protein deviation (GPD) in seven field trials. Fourteen candidate genes involved in several processes related to nitrogen metabolism were precisely located on two high-density consensus maps of common and durum wheat, and six of them were found to be highly associated with both traits. The wheat collection was genotyped using the 90 K iSelect array, and 11 stable quantitative trait loci (QTL) for GPC were detected in at least three environments and the mean across environments by the genome-wide association mapping. Interestingly, seven QTL were co-migrating with N-related candidate genes. Four QTL were found to be significantly associated to increases of GPD, indicating that selecting for GPC could not affect final grain yield per spike. The combined approaches of candidate genes and genome-wide association mapping led to a better understanding of the genetic relationships between grain storage proteins and grain yield per spike, and provided useful information for marker-assisted selection programs.

Summary Soybean is one of the most economically important crops worldwide and an important source of unsaturated fatty acids and protein for the human diet. Consumer demand for healthy fats and oils is increasing, and the global demand for vegetable oil is expected to double by 2050. Identification of key genes that regulate seed fatty acid content can facilitate molecular breeding of high‐quality soybean varieties with enhanced fatty acid profiles. Here, we analysed the genetic architecture underlying variations in soybean seed fatty acid content using 547 accessions, including mainly landraces and cultivars from northeastern China. Through fatty acid profiling, genome re‐sequencing, population genomics analyses, and GWAS, we identified a SEIPIN homologue at the FA9 locus as an important contributor to seed fatty acid content. Transgenic and multiomics analyses confirmed that FA9 was a key regulator of seed fatty acid content with pleiotropic effects on seed protein and seed size. We identified two major FA9 haplotypes in 1295 resequenced soybean accessions and assessed their phenotypic effects in a field planting of 424 accessions. Soybean accessions carrying FA9H2 had significantly higher total fatty acid contents and lower protein contents than those carrying FA9H1. FA9H2 was absent in wild soybeans but present in 13% of landraces and 26% of cultivars, suggesting that it may have been selected during soybean post‐domestication improvement. FA9 therefore represents a useful genetic resource for molecular breeding of high‐quality soybean varieties with specific seed storage profiles.

Autophagy is essential for nutrient recycling and plays a fundamental role in seed production and grain filling in plants. Autophagy participates in nitrogen remobilization at the whole-plant level, and the seeds of autophagy mutants present abnormal C and N contents relative to wild-type (WT) plants. It is well known that autophagy (ATG) genes are induced in leaves during senescence; however, expression of such genes in seeds has not yet been reported. In this study we show that most of the ATG genes are induced during seed maturation in Arabidopsis siliques. Promoter-ATG8f::UIDA and promoter-ATG8f::GFP fusions showed the strong expression of ATG8f in the phloem companion cells of pericarps and the funiculus, and in the embryo. Expression was especially strong at the late stages of development. The presence of many GFP-ATG8 pre-autophagosomal structures and autophagosomes confirmed the presence of autophagic activity in WT seed embryos. Seeds of atg5 and WT plants grown under low-or high-nitrate conditions were analysed. Nitrate-independent phenotypes were found with higher seed abortion in atg5 and early browing, higher total protein concentrations in the viable seeds of this mutant as compared to the WT. The higher total protein accumulation in atg5 viable seeds was significant from early developmental stages onwards. In addition, relatively low and early accumulation of 12S globulins were found in atg5 seeds. These features led us to the conclusion that atg5 seed development is accelerated and that the protein storage deposition pathway is somehow abnormal or incomplete.

Background Soybean is a globally important legume crop that provides a primary source of high-quality vegetable protein and oil. Seed protein content (SPC) is a valuable quality trait controlled by multiple genes in soybean. Results In this study, we performed quantitative trait loci (QTL) mapping, QTL-seq, and RNA sequencing (RNA-seq) to reveal the genes controlling protein content in the soybean by using the high protein content variety Nanxiadou 25. A total of 50 QTL for SPC distributed on 14 chromosomes except chromosomes 4, 12, 14, 17, 18, and 19 were identified by QTL mapping using 178 recombinant inbred lines (RILs). Among these QTL, the major QTL q SPC _20–1 and q SPC _20–2 on chromosome 20 were repeatedly detected across six tested environments, corresponding to the location of the major QTL detected using whole-genome sequencing-based QTL-seq. 329 candidate DEGs were obtained within the QTL region of q SPC _20–1 and q SPC _20–2 via gene expression profile analysis. Nine of which were associated with SPC, potentially representing candidate genes. Clone sequencing results showed that different single nucleotide polymorphisms (SNPs) and indels between high and low protein genotypes in Glyma.20G088000 and Glyma.16G066600 may be the cause of changes in this trait. Conclusions These results provide the basis for research on candidate genes and marker-assisted selection (MAS) in soybean breeding for seed protein content.

The grain protein content (GPC) of rice is an important factor that determines its nutritional, cooking, and eating qualities. To date, although a number of genes affecting GPC have been identified in rice, most of them have been cloned using mutants, and only a few genes have been cloned in the natural population. In this study, 135 significant loci were detected in a genome-wide association study (GWAS), many of which could be repeatedly detected across different years and populations. Four minor quantitative trait loci affecting rice GPC at four significant association loci, qPC2.1 , qPC7.1 , qPC7.2 , and qPC1.1 , were further identified and validated in near-isogenic line F 2 populations (NIL-F 2 ), explaining 9.82, 43.4, 29.2, and 13.6% of the phenotypic variation, respectively. The role of the associated flo5 was evaluated with knockdown mutants, which exhibited both increased grain chalkiness rate and GPC. Three candidate genes in a significant association locus region were analyzed using haplotype and expression profiles. The findings of this study will help elucidate the genetic regulatory network of protein synthesis and accumulation in rice through cloning of GPC genes and provide new insights on dominant alleles for marker-assisted selection in the genetic improvement of rice grain quality.

Summary The husk leaf of maize (Zea mays) encases the ear as a modified leaf and plays pivotal roles in protecting the ear from pathogen infection, translocating nutrition for grains and warranting grain yield. However, the natural genetic basis for variation in husk leaf width remains largely unexplored. Here, we performed a genome‐wide association study for maize husk leaf width and identified a 3‐bp InDel (insertion/deletion) in the coding region of the nitrate transporter gene ZmNRT2.5. This polymorphism altered the interaction strength of ZmNRT2.5 with another transporter, ZmNPF5, thereby contributing to variation in husk leaf width. We also isolated loss‐of‐function mutants in ZmNRT2.5, which exhibited a substantial decrease in husk leaf width relative to their controls. We demonstrate that ZmNRT2.5 facilitates the transport of nitrate from husk leaves to maize kernels in plants grown under low‐nitrogen conditions, contributing to the accumulation of proteins in maize seeds. Together, our findings uncovered a key gene controlling maize husk leaf width and nitrate transport from husk leaves to kernels. Identification of the ZmNRT2.5 loci offers direct targets for improving the protein content of maize seeds via molecular‐assisted maize breeding.

The grain protein content is an important quality trait in cereals, and the expression level of the OsAAP6 can significantly affect the grain protein content in rice. Through site-directed mutagenesis, we found that the position from −7 to −12 bp upstream of the transcription start site of the OsAAP6 was the functional variation site. By using the yeast single hybrid test, point-to-point in yeast, and the local surface plasmon resonance test, the OsNAC74 was screened and verified to be a regulator upstream of OsAAP6 . The OsNAC74 is a constitutively expressed gene whose product is located on the cell membrane. The OsAAP6 and the genes related to the seed storage in the Osnac74 mutants were downregulated, and grain protein content was significantly reduced. In addition, OsNAC74 had a significant impact on quality traits such as grain chalkiness and gel consistency in rice. Although the Osnac74 mutant seeds were relatively small, the individual plant yield was not decreased. Therefore, OsNAC74 is an important regulatory factor with multiple biological functions. This study provides important information for the later use of OsNAC74 gene for molecular design and breeding in rice.

Aim Attempts to increase grain protein content (GPC) most often result in a reduction in yield in cereals. This trade-off between GPC and yield could arise mainly because of the shared source of reductants for carbon and nitrogen assimilation. The primary aim of this study was to investigate whether the negative relationship between yield and GPC is primarily influenced by the availability of reductants for carbon and nitrogen assimilation. Methods Based on the initial screening of ten high-yielding rice genotypes, we identified two genotypes contrasting in GPC with comparable yield and photosynthesis. This was the most appropriate set to assess the interrelationship between carbon and nitrogen assimilation among the contrasts under ambient (~ 1500 µmole m −2  s −1 ) and low light intensities (~ 300 µmole m −2  s −1 ). Results Data suggest that triose phosphate utilization (TPU) limitation acts as a switch between carbon and nitrogen assimilation. Under ambient conditions, the high GPC genotype effectively managed the flow of electrons to carbon assimilation and diverted the excess electrons to other sinks. The diversion of extra electrons, particularly to nitrite reduction, was boosted by increased substrates from higher uptake, transport, and metabolism of nitrogen in leaves. In low GPC genotype, under ambient condition, excess electrons were quenched in the form of heat. Conclusions The current study suggests that an efficient utilization of electrons by adopting a switch called TPU limitation coupled with better uptake of nitrogen and remobilization efficiency can be a promising genotype for breeders to develop a high yielding variety complemented with high GPC.