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Background Soybean is an economically important crop which flowers predominantly in response to photoperiod. Several major loci controlling the quantitative trait for reproductive timing have been identified, of which allelic combinations at three of these loci, E1, E2, and E3, are the dominant factors driving time to flower and reproductive period. However, functional genomics studies have identified additional loci which affect reproductive timing, many of which are less understood. A better characterization of these genes will enable fine-tuning of adaptation to various production environments. Two such genes, E1La and E1Lb, have been implicated in flowering by previous studies, but their effects have yet to be assessed under natural photoperiod regimes. Results Natural and induced variants of E1La and E1Lb were identified and introgressed into lines harboring either E1 or its early flowering variant, e1-as. Lines were evaluated for days to flower and maturity in a Maturity Group (MG) III production environment. These results revealed that variation in E1La and E1Lb promoted earlier flowering and maturity, with stronger effects in e1-as background than in an E1 background. The geographic distribution of E1La alleles among wild and cultivated soybean revealed that natural variation in E1La likely contributed to northern expansion of wild soybean, while breeding programs in North America exploited e1-as to develop cultivars adapted to northern latitudes. Conclusion This research identified novel alleles of the E1 paralogues, E1La and E1Lb, which promote flowering and maturity under natural photoperiods. These loci represent sources of genetic variation which have been under-utilized in North American breeding programs to control reproductive timing, and which can be valuable additions to a breeder’s molecular toolbox.

Plants produce phylogenetically and spatially restricted, as well as structurally diverse specialized metabolites via multistep metabolic pathways. Hallmarks of specialized metabolic evolution include enzymatic promiscuity and recruitment of primary metabolic enzymes and examples of genomic clustering of pathway genes. Solanaceae glandular trichomes produce defensive acylsugars, with sidechains that vary in length across the family. We describe a tomato gene cluster on chromosome 7 involved in medium chain acylsugar accumulation due to trichome specific acyl-CoA synthetase and enoyl-CoA hydratase genes. This cluster co-localizes with a tomato steroidal alkaloid gene cluster and is syntenic to a chromosome 12 region containing another acylsugar pathway gene. We reconstructed the evolutionary events leading to this gene cluster and found that its phylogenetic distribution correlates with medium chain acylsugar accumulation across the Solanaceae. This work reveals insights into the dynamics behind gene cluster evolution and cell-type specific metabolite diversity., eLife digest Plants produce a vast variety of different molecules known as secondary or specialized metabolites to attract pollinating insects, such as bees, or protect themselves against herbivores and pests. The secondary metabolites are made from simple building blocks that are readily available in plants, including amino acids, fatty acids and sugars. Different species of plant, and even different parts of the same plant, produce their own sets of secondary metabolites. For example, the hairs on the surface of tomatoes and other members of the nightshade family of plants make metabolites known as acylsugars. These chemicals deter herbivores and pests from damaging the plants. To make acylsugars, the plants attach long chains known as fatty acyl groups to molecules of sugar, such as sucrose. Some members of the nightshade family produce acylsugars with longer chains than others. In particular, acylsugars with long chains are only found in tomatoes and other closely-related species. It remained unclear how the nightshade family evolved to produce acylsugars with chains of different lengths. To address this question, Fan et al. used genetic and biochemical approaches to study tomato plants and other members of the nightshade family. The experiments identified two genes known as AACS and AECH in tomatoes that produce acylsugars with long chains. These two genes originated from the genes of older enzymes that metabolize fatty acids – the building blocks of fats – in plant cells. Unlike the older genes, AACS and AECH were only active at the tips of the hairs on the plant’s surface. Fan et al. then investigated the evolutionary relationship between 11 members of the nightshade family and two other plant species. This revealed that AACS and AECH emerged in the nightshade family around the same time that longer chains of acylsugars started appearing. These findings provide insights into how plants evolved to be able to produce a variety of secondary metabolites that may protect them from a broader range of pests. The gene cluster identified in this work could be used to engineer other species of crop plants to start producing acylsugars as natural pesticides.

Soybean plays an important role in seed oil production for foods and industrial products in the USA. Chemical hydrogenation of commodity soybean oil increased functionality but unavoidably created trans fat which has been linked to many health issues in humans. An alternative to using hydrogenation of the oil to enhance oxidative stability is to genetically increase the level of oleic acid in the seed oil. Our goal was to develop a soybean germplasm as a source for more functional soybean oil with a high oleic acid, increased stearic acid, and low linolenic acid profile utilizing new and existing variant alleles of key fatty acid desaturase genes. Using forward genetics, novel alleles of FAD2-1A were discovered and characterized from a mutant soybean population already containing elevated seed stearic acid content. One of the two new FAD2-1A alleles, when combined with existing mutant alleles of FAD2-1B created a high oleic acid seed oil phenotype in soybean germplasm lines. The other new FAD2-1A allele produced lower and more variable oleic acid levels when combined with existing mutant alleles of FAD2-1B. Seed stearic acid increased to ~ 10–11% in lines containing combinations of FAD2-1A and FAD2-1B mutant alleles plus the SACPD-C missense mutant alleles; however, the increase in stearic acid was associated with a decrease in the oleic acid content and did not meet the target of at least 20% stearic acid in the seed oil. In addition, existing FAD3 mutant alleles were incorporated into the novel high oleic acid and high oleic/elevated stearic acid soybean lines with four or five targeted alleles combined (FAD2-1A, FAD2-1B, FAD3A, FAD3C, and SACPD-C) to create soybean germplasm with more functional soybean oil. This study is beneficial for improving the quality of soybean oil based on nutritional value and oxidative stability.

Carbon nanotube salts, prepared by treating single-walled carbon nanotubes (SWNTs) with lithium in liquid ammonia, react with N-halosuccinimide by electron transfer to generate transient radical anions that yield succinimidyl radicals and halide anions. Similarly, alkyl peroxides, when treated with SWNT salts, give rise to alkoxy radicals and alkoxides. The free radicals add to the sidewalls of nanotube salts to form succinimidyl and alkoxy derivatized SWNTs. The functionalized SWNTs can then be converted to amino and hydroxyl SWNTs by hydrolysis with hydrazine or with fuming sulfuric acid, respectively. Hydrolysis of alkoxy derivatized SWNTs with D2O/D2SO4 led to the deuterated analogue of hydroxy SWNT, as shown by Fourier transform infrared (FTIR) spectroscopy. These reactions constitute a two-step synthesis of aminated and hydroxylated SWNTs. Covalent sidewall functionalization was confirmed by thermal gravimetric analysis (TGA), Raman spectroscopy, FTIR spectroscopy, and high-resolution transmission e...