The genome of the recently domesticated crop plant sugar beet (Beta vulgaris)

Spinach genomes reveal migration history and candidate genes for important crop traits

Spinach (Spinacia oleracea) is an important leafy crop possessing notable economic value and health benefits. Current genomic resources include reference genomes and genome-wide association studies. However, the worldwide genetic relationships and the migration history of the crop remained uncertain, and genome-wide association studies have produced extensive gene lists related to agronomic traits. Here, we re-analysed the sequenced genomes of 305 cultivated and wild spinach accessions to unveil the phylogeny and history of cultivated spinach and to explore genetic variation in relation to phenotypes. In contrast to previous studies, we employed machine learning methods (based on Extreme Gradient Boosting, XGBoost) to detect variants that are collectively associated with agronomic traits. Variant-based cluster analyses revealed three primary spinach groups in the Middle East, Asia and Europe/US. Combining admixture analysis and allele-sharing statistics, migration routes of spinach from the Middle East to Europe and Asia are presented. Using XGBoost machine learning models we predict genomic variants influencing bolting time, flowering time, petiole color, and leaf surface texture and propose candidate genes for each trait. This study enhances our understanding of the history and phylogeny of domesticated spinach and provides valuable information on candidate genes for future genetic improvement of the crop.

SOS1 tonoplast neo-localization and the RGG protein SALTY are important in the extreme salinity tolerance of Salicornia bigelovii

The identification of genes involved in salinity tolerance has primarily focused on model plants and crops. However, plants naturally adapted to highly saline environments offer valuable insights into tolerance to extreme salinity. Salicornia plants grow in coastal salt marshes, stimulated by NaCl. To understand this tolerance, we generated genome sequences of two Salicornia species and analyzed the transcriptomic and proteomic responses of Salicornia bigelovii to NaCl. Subcellular membrane proteomes reveal that SbiSOS1, a homolog of the well-known SALT-OVERLY-SENSITIVE 1 (SOS1) protein, appears to localize to the tonoplast, consistent with subcellular localization assays in tobacco. This neo-localized protein can pump Na+ into the vacuole, preventing toxicity in the cytosol. We further identify 11 proteins of interest, of which SbiSALTY, substantially improves yeast growth on saline media. Structural characterization using NMR identified it as an intrinsically disordered protein, localizing to the endoplasmic reticulum in planta, where it can interact with ribosomes and RNA, stabilizing or protecting them during salt stress.

Shared xerophytic genes and their re-use in local adaptation to aridity in the desert plant Gymnocarpos przewalskii

In order to thrive and survive, plant species need to combine stability in the long term and rapid response to environmental challenges in the short term. The former would be reflected by parallel or convergent adaptation across species, and the latter by pronounced local adaptation among populations of the same species. In the present study, we generated a high-quality genome and re-sequenced 177 individuals for Gymnocarpos przewalskii, an important desert plant species from North-West China, to detect local adaptation. We first focus on ancient adaptation to aridity at the molecular level by comparing the genomic data of 15 species that vary in their ability to withstand aridity. We found that a total of 118 genes were shared across xerophytic species but absent from non-xerophytic species. Of the 65 found in G. przewalskii, 63 were under purifying selection and two under positive selection. We then focused on local adaptation. Up to 20% of the G. przewalskii genome showed signatures of local adaptation to aridity during population divergence. Thirteen of the selected shared xerophytic genes were reused in local adaptation after population differentiation. Hence, only about 20% of the genes shared and specific to xerophytic species and associated with adaptation to aridity were later recruited for local adaptation in G. przewalskii.

Sugar beet PMT5a and STP13 carriers suitable for proton-driven plasma membrane sucrose and glucose import in taproots

Sugar beet (Beta vulgaris) is the major sugar-producing crop in Europe and Northern America, as the taproot stores sucrose at a concentration of around 20%. Genome sequence analysis together with biochemical and electrophysiological approaches led to the identification and characterization of the TST sucrose transporter driving vacuolar sugar accumulation in the taproot. However, the sugar transporters mediating sucrose uptake across the plasma membrane of taproot parenchyma cells remained unknown. As with glucose, sucrose stimulation of taproot parenchyma cells caused inward proton fluxes and plasma membrane depolarization, indicating a sugar/proton symport mechanism. To decipher the nature of the corresponding proton-driven sugar transporters, we performed taproot transcriptomic profiling and identified the cold-induced PMT5a and STP13 transporters. When expressed in Xenopus laevis oocytes, BvPMT5a was characterized as a voltage- and H+-driven low-affinity glucose transporter, which does not transport sucrose. In contrast, BvSTP13 operated as a high-affinity H+/sugar symporter, transporting glucose better than sucrose, and being more cold-tolerant than BvPMT5a. Modeling of the BvSTP13 structure with bound mono- and disaccharides suggests plasticity of the binding cleft to accommodate the different saccharides. The identification of BvPMT5a and BvSTP13 as taproot sugar transporters could improve breeding of sugar beet to provide a sustainable energy crop.

Isoform-resolved genome annotation enables mapping of tissue-specific betalain regulation in amaranth

Betalains are coloring pigments produced in some families of the order Caryophyllales, where they replace anthocyanins as coloring pigments. While the betalain pathway itself is well studied, the tissue-specific regulation of the pathway remains mostly unknown. We enhance the high-quality Amaranthus hypochondriacus reference genome and produce a substantially more complete genome annotation, incorporating isoform details. We annotate betalain and anthocyanin pathway genes along with their regulators in amaranth and map the genetic control and tissue-specific regulation of the betalain pathway. Our improved genome annotation allowed us to identify causal mutations that lead to a knock-out of red betacyanins in natural accessions of amaranth. We reveal the tissue-specific regulation of flower color via a previously uncharacterized MYB transcription factor, AhMYB2. Downregulation of AhMYB2 in the flower leads to reduced expression of key betalain enzyme genes and loss of red flower color. Our improved amaranth reference genome represents the most complete genome of amaranth to date and is a valuable resource for betalain and amaranth research. High similarity of the flower betalain regulator AhMYB2 to anthocyanin regulators and a partially conserved interaction motif support the co-option of anthocyanin regulators for the betalain pathway as a possible reason for the mutual exclusiveness of the two pigments.

Repeat turnover meets stable chromosomes: repetitive DNA sequences mark speciation and gene pool boundaries in sugar beet and wild beets

Sugar beet and its wild relatives share a base chromosome number of nine and similar chromosome morphologies. Yet, interspecific breeding is impeded by chromosome and sequence divergence that is still not fully understood. Since repetitive DNAs are among the fastest evolving parts of the genome, we investigated, if repeatome innovations and losses are linked to chromosomal differentiation and speciation. We traced genome and chromosome-wide evolution across 13 beet species comprising all sections of the genera Beta and Patellifolia. For this, we combined short and long read sequencing, flow cytometry, and cytogenetics to build a comprehensive framework that spans the complete scale from DNA to chromosome to genome. Genome sizes and repeat profiles reflect the separation into three gene pools with contrasting evolutionary patterns. Among all repeats, satellite DNAs harbor most genomic variability, leading to fundamentally different centromere architectures, ranging from chromosomal uniformity in Beta and Patellifolia to the formation of patchwork chromosomes in Corollinae/Nanae. We show that repetitive DNAs are causal for the genome expansions and contractions across the beet genera, providing insights into the genomic underpinnings of beet speciation. Satellite DNAs in particular vary considerably between beet genomes, leading to the evolution of distinct chromosomal setups in the three gene pools, likely contributing to the barriers in beet breeding. Thus, with their isokaryotypic chromosome sets, beet genomes present an ideal system for studying the link between repeats, genomic variability, and chromosomal differentiation and provide a theoretical fundament for understanding barriers in any crop breeding effort.

Genome-Wide Comparative Analysis of Five Amaranthaceae Species Reveals a Large Amount of Repeat Content

Amaranthus is a genus of C4 dicotyledonous herbaceous plant species that are widely distributed in Asia, Africa, Australia, and Europe and are used as grain, vegetables, forages, and ornamental plants. Amaranth species have gained significant attention nowadays as potential sources of nutritious food and industrial products. In this study, we performed a comparative genome analysis of five amaranth species, namely, Amaranthus hypochondriacus, Amaranthus tuberculatus, Amaranthus hybridus, Amaranthus palmeri, and Amaranthus cruentus. The estimated repeat content ranged from 54.49% to 63.26% and was not correlated with the genome sizes. Out of the predicted repeat classes, the majority of repetitive sequences were Long Terminal Repeat (LTR) elements, which account for about 13.91% to 24.89% of all amaranth genomes. Phylogenetic analysis based on 406 single-copy orthologous genes revealed that A. hypochondriacus is most closely linked to A. hybridus and distantly related to A. cruentus. However, dioecious amaranth species, such as A. tuberculatus and A. palmeri, which belong to the subgenera Amaranthus Acnida, have formed their distinct clade. The comparative analysis of genomic data of amaranth species will be useful to identify and characterize agronomically important genes and their mechanisms of action. This will facilitate genomics-based, evolutionary studies, and breeding strategies to design faster, more precise, and predictable crop improvement programs.

Genome-wide identification, phylogenetic classification of histone acetyltransferase genes, and their expression analysis in sugar beet (Beta vulgaris L.) under salt stress

MAIN CONCLUSION

This study identified seven histone acetyltransferase-encoding genes (HATs) from Beta vulgaris L. (sugar beet) genome through bioinformatics tools and analyzed their expression profiles under salt stress. Sugar beet HATs are phylogenetically divided into four families: GNAT, MYST, CBP, and TAFII250. The BvHAT genes were differentially transcribed in leaves, stems, and roots of B. vulgaris salt-resistant (Casino) and -sensitive (Bravo) cultivars under salt stress. Histone acetylation is regulated by histone acetyltransferases (HATs), which catalyze ɛ-amino bond formation between lysine residues and acetyl groups with a cofactor, acetyl-CoA. Even though the HATs are known to participate in stress response and development in model plants, little is known about the functions of HATs in crops. In sugar beet (Beta vulgaris L.), they have not yet been identified and characterized. Here, an in silico analysis of the HAT gene family in sugar beet was performed, and their expression patterns in leaves, stems, and roots of B. vulgaris were analyzed under salt stress. Salt-resistant (Casino) and -sensitive (Bravo) beet cultivars were used for gene expression assays. Seven HATs were identified from sugar beet genome, and named BvHAG1, BvHAG2, BvHAG3, BvHAG4, BvHAC1, BvHAC2, and BvHAF1. The HAT proteins were divided into 4 groups including MYST, GNAT (GCN5, HAT1, ELP3), CBP and TAFII250. Analysis of cis-acting elements indicated that the BvHAT genes might be involved in hormonal regulation, light response, plant development, and abiotic stress response. The BvHAT genes were differentially expressed in leaves, stems, and roots under control and 300 mM NaCl. In roots of B. vulgaris cv. Bravo, the BvHAG1, BvHAG2, BvHAG4, BvHAF1, and BvHAC1 genes were dramatically expressed after 7 and 14 days of salt stress. Interestingly, the BvHAC2 gene was not expressed under both control and stress conditions. However, the expression of BvHAG2, BvHAG3, BvHAG4, BvHAC1, BvHAC2 genes showed a significant increase in response to salt stress in the roots of cv. Casino. This study provides new insights into the potential roles of histone acetyltransferases in sugar beet.

Transcriptomic and metabolomic changes in postharvest sugarbeet roots reveal widespread metabolic changes in storage and identify genes potentially responsible for respiratory sucrose loss

Endogenous metabolism is primarily responsible for losses in sucrose content and processing quality in postharvest sugarbeet roots. The genes responsible for this metabolism and the transcriptional changes that regulate it, however, are largely unknown. To identify genes and metabolic pathways that participate in postharvest sugarbeet root metabolism and the transcriptional changes that contribute to their regulation, transcriptomic and metabolomic profiles were generated for sugarbeet roots at harvest and after 12, 40 and 120 d storage at 5 and 12°C and gene expression and metabolite concentration changes related to storage duration or temperature were identified. During storage, 8656 genes, or 34% of all expressed genes, and 225 metabolites, equivalent to 59% of detected metabolites, were altered in expression or concentration, indicating extensive transcriptional and metabolic changes in stored roots. These genes and metabolites contributed to a wide range of cellular and molecular functions, with carbohydrate metabolism being the function to which the greatest number of genes and metabolites classified. Because respiration has a central role in postharvest metabolism and is largely responsible for sucrose loss in sugarbeet roots, genes and metabolites involved in and correlated to respiration were identified. Seventy-five genes participating in respiration were differentially expressed during storage, including two bidirectional sugar transporter SWEET17 genes that highly correlated with respiration rate. Weighted gene co-expression network analysis identified 1896 additional genes that positively correlated with respiration rate and predicted a pyruvate kinase gene to be a central regulator or biomarker for respiration rate. Overall, these results reveal the extensive and diverse physiological and metabolic changes that occur in stored sugarbeet roots and identify genes with potential roles as regulators or biomarkers for respiratory sucrose loss.

High-fidelity (repeat) consensus sequences from short reads using combined read clustering and assembly

BACKGROUND

Despite the many cheap and fast ways to generate genomic data, good and exact genome assembly is still a problem, with especially the repeats being vastly underrepresented and often misassembled. As short reads in low coverage are already sufficient to represent the repeat landscape of any given genome, many read cluster algorithms were brought forward that provide repeat identification and classification. But how can trustworthy, reliable and representative repeat consensuses be derived from unassembled genomes?

RESULTS

Here, we combine methods from repeat identification and genome assembly to derive these robust consensuses. We test several use cases, such as (1) consensus building from clustered short reads of non-model genomes, (2) from genome-wide amplification setups, and (3) specific repeat-centred questions, such as the linked vs. unlinked arrangement of ribosomal genes. In all our use cases, the derived consensuses are robust and representative. To evaluate overall performance, we compare our high-fidelity repeat consensuses to RepeatExplorer2-derived contigs and check, if they represent real transposable elements as found in long reads. Our results demonstrate that it is possible to generate useful, reliable and trustworthy consensuses from short reads by a combination from read cluster and genome assembly methods in an automatable way.

CONCLUSION

We anticipate that our workflow opens the way towards more efficient and less manual repeat characterization and annotation, benefitting all genome studies, but especially those of non-model organisms.

Genome-wide identification, evolution, and role of SPL gene family in beet (Beta vulgaris L.) under cold stress

BACKGROUND

SPL transcription factors play vital roles in regulating plant growth, development, and abiotic stress responses. Sugar beet (Beta vulgaris L.), one of the world's main sugar-producing crops, is a major source of edible and industrial sugars for humans. Although the SPL gene family has been extensively identified in other species, no reports on the SPL gene family in sugar beet are available.

RESULTS

Eight BvSPL genes were identified at the whole-genome level and were renamed based on their positions on the chromosome. The gene structure, SBP domain sequences, and phylogenetic relationship with Arabidopsis were analyzed for the sugar beet SPL gene family. The eight BvSPL genes were divided into six groups (II, IV, V, VI, VII, and VIII). Of the BvSPL genes, no tandem duplication events were found, but one pair of segmental duplications was present. Multiple cis-regulatory elements related to growth and development were identified in the 2000-bp region upstream of the BvSPL gene start codon (ATG). Using quantitative real-time polymerase chain reaction (qRT-PCR), the expression profiles of the eight BvSPL genes were examined under eight types of abiotic stress and during the maturation stage. BvSPL transcription factors played a vital role in abiotic stress, with BvSPL3 and BvSPL6 being particularly noteworthy.

CONCLUSION

Eight sugar beet SPL genes were identified at the whole-genome level. Phylogenetic trees, gene structures, gene duplication events, and expression profiles were investigated. The qRT-PCR analysis indicated that BvSPLs play a substantial role in the growth and development of sugar beet, potentially participating in the regulation of root expansion and sugar accumulation.

Genotype by environment and genotype by yield*trait interactions in sugar beet: analyzing yield stability and determining key traits association

The genotype by environment interaction significantly influences plant yield, making it imperative to understand its nature for the creation of breeding programs to enhance crop production. However, this is not the only obstacle in the yield improvement process. Breeders also face the significant challenge of unfavorable and negative correlations among key traits. In this study, the stability of root yield and white sugar yield, and the association between the key traits of root yield, sugar content, nitrogen, sodium, and potassium were examined in 20 sugar beet genotypes. The study was conducted using a randomized complete block design with four replications over two consecutive years across five locations. The combined analysis of variance results revealed significant main effects of year, location, and genotype on both root yield and white sugar yield. Notably, two-way and three-way interactions between these main effects on root yield and white sugar yield resulted in a significant difference. The additive main effect and multiplicative interaction analysis revealed that the first five interaction principal components significantly impacted both the root yield and white sugar yield. The linear mixed model results for root yield and white sugar yield indicated that the genotype effect and the genotype by environment interaction were significant. The weighted average absolute scores of the best linear unbiased predictions biplot demonstrated that genotypes 20, 4, 7, 2, 16, 3, 6, 1, 14, and 15 were superior in terms of root yield. For white sugar yield, genotypes 4, 16, 3, 7, 5, 1, 10, 20, 2, and 6 stood out. These genotypes were not only stable but also had a yield value higher than the total average. All key traits, which include sugar content, sodium, potassium, and alpha amino nitrogen, demonstrated a negative correlation with root yield. Based on the genotype by yield*trait analysis results, genotypes 20, 19, and 16 demonstrated optimal performance when considering the combination of root yield with sugar content, sodium, alpha amino nitrogen, and potassium. The multi-trait stability study, genotype 13 ranked first, and genotypes 10, 8, and 9 were identified as the most ideal stable genotypes across all traits. According to the multi-trait stability index, genotype 13 emerged as the top-ranking genotype. Additionally, genotypes 10, 8, and 9 were recognized as the most stable genotypes.

Molecular signatures of alternative reproductive strategies in a facultatively social hover wasp

Social insect reproductives and non-reproductives represent ideal models with which to understand the expression and regulation of alternative phenotypes. Most research in this area has focused on the developmental regulation of reproductive phenotypes in obligately social taxa such as honey bees, while relatively few studies have addressed the molecular correlates of reproductive differentiation in species in which the division of reproductive labour is established only in plastic dominance hierarchies. To address this knowledge gap, we generate the first genome for any stenogastrine wasp and analyse brain transcriptomic data for non-reproductives and reproductives of the facultatively social species Liostenogaster flavolineata, a representative of one of the simplest forms of social living. By experimentally manipulating the reproductive 'queues' exhibited by social colonies of this species, we show that reproductive division of labour in this species is associated with transcriptomic signatures that are more subtle and variable than those observed in social taxa in which colony living has become obligate; that variation in gene expression among non-reproductives reflects their investment into foraging effort more than their social rank; and that genes associated with reproductive division of labour overlap to some extent with those underlying division of labour in the separate polistine origin of wasp sociality but only explain a small portion of overall variation in this trait. These results indicate that broad patterns of within-colony transcriptomic differentiation in this species are similar to those in Polistinae but offer little support for the existence of a strongly conserved 'toolkit' for sociality.

Genomic characterization of a nematode tolerance locus in sugar beet

BACKGROUND

Infection by beet cyst nematodes (BCN, Heterodera schachtii) causes a serious disease of sugar beet, and climatic change is expected to improve the conditions for BCN infection. Yield and yield stability under adverse conditions are among the main breeding objectives. Breeding of BCN tolerant sugar beet cultivars offering high yield in the presence of the pathogen is therefore of high relevance.

RESULTS

To identify causal genes providing tolerance against BCN infection, we combined several experimental and bioinformatic approaches. Relevant genomic regions were detected through mapping-by-sequencing using a segregating F2 population. DNA sequencing of contrasting F2 pools and analyses of allele frequencies for variant positions identified a single genomic region which confers nematode tolerance. The genomic interval was confirmed and narrowed down by genotyping with newly developed molecular markers. To pinpoint the causal genes within the potential nematode tolerance locus, we generated long read-based genome sequence assemblies of the tolerant parental breeding line Strube U2Bv and the susceptible reference line 2320Bv. We analyzed continuous sequences of the potential locus with regard to functional gene annotation and differential gene expression upon BCN infection. A cluster of genes with similarity to the Arabidopsis thaliana gene encoding nodule inception protein-like protein 7 (NLP7) was identified. Gene expression analyses confirmed transcriptional activity and revealed clear differences between susceptible and tolerant genotypes.

CONCLUSIONS

Our findings provide new insights into the genomic basis of plant-nematode interactions that can be used to design and accelerate novel management strategies against BCN.

Gene duplications facilitate C4-CAM compatibility in common purslane

Common purslane (Portulaca oleracea) integrates both C4 and crassulacean acid metabolism (CAM) photosynthesis pathways and is a promising model plant to explore C4-CAM plasticity. Here, we report a high-quality chromosome-level genome of nicotinamide adenine dinucleotide (NAD)-malic enzyme (ME) subtype common purslane that provides evidence for 2 rounds of whole-genome duplication (WGD) with an ancient WGD (P-β) in the common ancestor to Portulacaceae and Cactaceae around 66.30 million years ago (Mya) and another (Po-α) specific to common purslane lineage around 7.74 Mya. A larger number of gene copies encoding key enzymes/transporters involved in C4 and CAM pathways were detected in common purslane than in related species. Phylogeny, conserved functional site, and collinearity analyses revealed that the Po-α WGD produced the phosphoenolpyruvate carboxylase-encoded gene copies used for photosynthesis in common purslane, while the P-β WGD event produced 2 ancestral genes of functionally differentiated (C4- and CAM-specific) beta carbonic anhydrases involved in the C4 + CAM pathways. Additionally, cis-element enrichment analysis in the promoters showed that CAM-specific genes have recruited both evening and midnight circadian elements as well as the Abscisic acid (ABA)-independent regulatory module mediated by ethylene-response factor cis-elements. Overall, this study provides insights into the origin and evolutionary process of C4 and CAM pathways in common purslane, as well as potential targets for engineering crops by integrating C4 or CAM metabolism.

A chromosome-level genome assembly provides insights into Cornus wilsoniana evolution, oil biosynthesis, and floral bud development

Cornus wilsoniana W. is a woody oil plant with high oil content and strong hypolipidemic effects, making it a valuable species for medicinal, landscaping, and ecological purposes in China. To advance genetic research on this species, we employed PacBio together with Hi-C data to create a draft genome assembly for C. wilsoniana. Based on an 11-chromosome anchored chromosome-level assembly, the estimated genome size was determined to be 843.51 Mb. The N50 contig size and N50 scaffold size were calculated to be 4.49 and 78.00 Mb, respectively. Furthermore, 30 474 protein-coding genes were annotated. Comparative genomics analysis revealed that C. wilsoniana diverged from its closest species ~12.46 million years ago (Mya). Furthermore, the divergence between Cornaceae and Nyssaceae occurred >62.22 Mya. We also found evidence of whole-genome duplication events and whole-genome triplication γ, occurring at ~44.90 and 115.86 Mya. We further inferred the origins of chromosomes, which sheds light on the complex evolutionary history of the karyotype of C. wilsoniana. Through transcriptional and metabolic analysis, we identified two FAD2 homologous genes that may play a crucial role in controlling the oleic to linoleic acid ratio. We further investigated the correlation between metabolites and genes and identified 33 MADS-TF homologous genes that may affect flower morphology in C. wilsoniana. Overall, this study lays the groundwork for future research aimed at identifying the genetic basis of crucial traits in C. wilsoniana.

Zinc and Boron Soil Applications Affect Athelia rolfsii Stress Response in Sugar Beet (Beta vulgaris L.) Plants

Generation of reactive oxygen species (ROS) constitutes an initial defense approach in plants during pathogen infection. Here, the effects of the two micronutrients, namely, zinc (Zn) and boron (B), on enzymatic and non-enzymatic antioxidant properties, as well as malondialdehyde (MDA) contents in leaves and roots challenged with Athelia rolfsii, which cause root rot disease, were investigated. The findings revealed that Zn and B application to the potting soil alleviated the adverse effect of A. rolfsii on sugar beet plants and increased the chlorophyll content in leaves. The increased enzymatic antioxidant activities such as catalase (CAT), peroxidase (POX), and ascorbate peroxidase (APX), and non-enzymatic antioxidants such as ascorbic acid (AsA) were observed in Zn applied plants compared to both uninoculated and inoculated control plants. A significant rise in CAT activity was noted in both leaves (335.1%) and roots (264.82%) due to the Zn2B1.5 + Ar treatment, in comparison to the inoculated control plants. On the other hand, B did not enhance the activity of any one of them except AsA. Meanwhile, A. rolfsii infection led to the increased accumulation of MDA content both in the leaves and roots of sugar beet plants. Interestingly, reduced MDA content was recorded in leaves and roots treated with both Zn and B. The results of this study demonstrate that both Zn and B played a vital role in A. rofsii tolerance in sugar beet, while Zn enhances antioxidant enzyme activities, B appeared to have a less pronounced effect on modulating the antioxidant system to alleviate the adverse effect of A. rolfsii.

Genome-Wide Analysis of Q-Type C2H2 ZFP Genes in Response to Biotic and Abiotic Stresses in Sugar Beet

A plant's Q-type C2H2-type ZFP plays key roles in plant growth and development and responses to biotic and abiotic stresses. Sugar beet (Beta vulgaris L.) is an important crop for sugar production. Salt stress and viral infection significantly reduce the root yield and sugar content of sugar beet. However, there is a lack of comprehensive genome-wide analyses of Q-type C2H2 ZFPs and their expression patterns in sugar beet under stress. In this study, 35 sugar beet Q-type C2H2 ZFPs (BvZFPs) containing at least one conserved "QALGGH" motif were identified via bioinformatics techniques using TBtools software. According to their evolutionary relationship, the BvZFPs were classified into five subclasses. Within each subclass, the physicochemical properties and motif compositions showed strong similarities. A Ka/Ks analysis indicated that the BvZFPs were conserved during evolution. Promoter cis-element analysis revealed that most BvZFPs are associated with elements related to phytohormone, biotic or abiotic stress, and plant development. The expression data showed that the BvZFPs in sugar beet are predominantly expressed in the root. In addition, BvZFPs are involved in the response to abiotic and biotic stresses, including salt stress and viral infection. Overall, these results will extend our understanding of the Q-type C2H2 gene family and provide valuable information for the biological breeding of sugar beet against abiotic and biotic stresses in the future.

Analysis of N6-methyladenosine reveals a new important mechanism regulating the salt tolerance of sugar beet (Beta vulgaris)

Salinity is an important environmental factor in crop growth and development. N6-methyladenosine (m6A) is an essential epigenetic modification that regulates plant-environment interaction. Sugar beet is a major sugar-yielding crop that has a certain tolerance to salt, but the dynamic response elicited by the m6A modification of transcripts under salt stress remains unknown. In this study, sugar beet was exposed to 300 mM NaCl to investigate its physiological response to high salinity and transcriptome-wide m6A modification profile. After the salt treatment, 7737 significantly modified m6A sites and 4981 differentially expressed genes (DEGs) were identified. Among the 312 m6A-modified DEGs, 113 hypomethylated DEGs were up-regulated and 99 hypermethylated DEGs were down-regulated, indicating a negative correlation between m6A modification and gene expression. Well-known salt tolerance genes (e.g., sodium/hydrogen exchanger 1, choline monooxygenase, and nucleoredoxin 2) and phospholipid signaling pathway genes (phosphoinositol-specific phospholipase C, phospholipase D, diacylglycerol kinase 1, etc.) were also among the m6A-modified genes. Further analysis showed that m6A modification may regulate salt-tolerant related gene expression by controlling mRNA stability. Therefore, changes in m6A modification may negatively regulate the expression of the salt-resistant genes in sugar beet, at least in part by modulating the stability of the mRNA via demethylase BvAlkbh10B. These findings could provide a better understanding of the epigenetic mechanisms of salt tolerance in sugar beets and uncover new candidate genes for improving the production of sugar beets planted in high-salinity soil.

Form and contour: breeding and genetics of organ shape from wild relatives to modern vegetable crops

Shape is a primary determinant of consumer preference for many horticultural crops and it is also associated with many aspects of marketing, harvest mechanics, and postharvest handling. Perceptions of quality and preference often map to specific shapes of fruits, tubers, leaves, flowers, roots, and other plant organs. As a result, humans have greatly expanded the palette of shapes available for horticultural crops, in many cases creating a series of market classes where particular shapes predominate. Crop wild relatives possess organs shaped by natural selection, while domesticated species possess organs shaped by human desires. Selection for visually-pleasing shapes in vegetable crops resulted from a number of opportunistic factors, including modification of supernumerary cambia, allelic variation at loci that control fundamental processes such as cell division, cell elongation, transposon-mediated variation, and partitioning of photosynthate. Genes that control cell division patterning may be universal shape regulators in horticultural crops, influencing the form of fruits, tubers, and grains in disparate species. Crop wild relatives are often considered less relevant for modern breeding efforts when it comes to characteristics such as shape, however this view may be unnecessarily limiting. Useful allelic variation in wild species may not have been examined or exploited with respect to shape modifications, and newly emergent information on key genes and proteins may provide additional opportunities to regulate the form and contour of vegetable crops.

Association analysis of agronomic traits and construction of genetic networks by resequencing of 306 sugar beet (Beta vulgaris L.) lines

Due to the relatively brief domestication history of sugar beet (Beta vulgaris ssp. vulgaris), our understanding of the genomic diversity and functional genes in its cultivars is limited, resulting in slow breeding progress. To address this issue, a total of 306 germplasm materials of major cultivars and breeding lines from China, the USA, and Europe were selected for genome resequencing. We investigated population structure and genetic diversity and performed selective scanning of genomic regions, identifying six novel genes associated with important agronomic traits: the candidate genes DFAX2 and P5CS for skin roughness; the candidate genes FRO5, GL24, and PPR91 for root yield and sugar yield, and the pleiotropic candidate gene POLX for flourishing growth vigour, plant height, crown size, flesh coarseness, and sugar yield. In addition, we constructed a protein-protein interaction network map and a phenotype-gene network map, which provide valuable information for identifying and characterizing functional genes affecting agronomic traits in sugar beet. Overall, our study sheds light on the future improvement of sugar beet agronomic traits at the molecular level.

Multi-omics data provide insight into the adaptation of the glasshouse plant Rheum nobile to the alpine subnival zone

Subnival glasshouse plants provide a text-book example of high-altitude adaptation with reproductive organs enclosed in specialized semi-translucent bracts, monocarpic reproduction and continuous survival under stress. Here, we present genomic, transcriptomic and metabolomic analyses for one such plant, the Noble rhubarb (Rheum nobile). Comparative genomic analyses show that an expanded number of genes and retained genes from two recent whole-genome duplication events are both relevant to subnival adaptation of this species. Most photosynthesis genes are downregulated within bracts compared to within leaves, and indeed bracts exhibit a sharp reduction in photosynthetic pigments, indicating that the bracts no longer perform photosynthesis. Contrastingly, genes related to flavonol synthesis are upregulated, providing enhanced defense against UV irradiation damage. Additionally, anatomically abnormal mesophyll combined with the downregulation of genes related to mesophyll differentiation in bracts illustrates the innovation and specification of the glass-like bracts. We further detect substantial accumulation of antifreeze proteins (e.g. AFPs, LEAs) and various metabolites (e.g. Proline, Protective sugars, procyanidins) in over-wintering roots. These findings provide new insights into subnival adaptation and the evolution of glasshouse alpine plants.

Chromosome-scale genome sequence of Suaeda glauca sheds light on salt stress tolerance in halophytes

Soil salinity is a growing concern for global crop production and the sustainable development of humanity. Therefore, it is crucial to comprehend salt tolerance mechanisms and identify salt-tolerance genes to enhance crop tolerance to salt stress. Suaeda glauca, a halophyte species well adapted to the seawater environment, possesses a unique ability to absorb and retain high salt concentrations within its cells, particularly in its leaves, suggesting the presence of a distinct mechanism for salt tolerance. In this study, we performed de novo sequencing of the S. glauca genome. The genome has a size of 1.02 Gb (consisting of two sets of haplotypes) and contains 54 761 annotated genes, including alleles and repeats. Comparative genomic analysis revealed a strong synteny between the genomes of S. glauca and Beta vulgaris. Of the S. glauca genome, 70.56% comprises repeat sequences, with retroelements being the most abundant. Leveraging the allele-aware assembly of the S. glauca genome, we investigated genome-wide allele-specific expression in the analyzed samples. The results indicated that the diversity in promoter sequences might contribute to consistent allele-specific expression. Moreover, a systematic analysis of the ABCE gene families shed light on the formation of S. glauca's flower morphology, suggesting that dysfunction of A-class genes is responsible for the absence of petals in S. glauca. Gene family expansion analysis demonstrated significant enrichment of Gene Ontology (GO) terms associated with DNA repair, chromosome stability, DNA demethylation, cation binding, and red/far-red light signaling pathways in the co-expanded gene families of S. glauca and S. aralocaspica, in comparison with glycophytic species within the chenopodium family. Time-course transcriptome analysis under salt treatments revealed detailed responses of S. glauca to salt tolerance, and the enrichment of the transition-upregulated genes in the leaves associated with DNA repair and chromosome stability, lipid biosynthetic process, and isoprenoid metabolic process. Additionally, genome-wide analysis of transcription factors indicated a significant expansion of FAR1 gene family. However, further investigation is needed to determine the exact role of the FAR1 gene family in salt tolerance in S. glauca.

Investigation of the expansin gene family in sugar beet (Beta vulgaris) by the genome-wide level and their expression responses under abiotic stresses

Sugar beet (Beta vulgaris ssp. vulgaris) is primarily used in sugar production worldwide. Expansins are a gene family of cell wall proteins effective in regulating cell wall structure. They also participate in developmental stages, including cell and leaf growth, root development, and fruit ripening. This study comprehensively characterizes the expansin gene family members found in the sugar beet genome. In addition, in silico expression analysis of sugar beet expansin genes under variable abiotic stress conditions and expression profiles of expansin genes under combined drought and heat stresses by the qRT-PCR method were evaluated in the study. A total of 31 sugar beet expansin genes were identified. BvuEXLA-02 and BvuEXLB-02 genes can have abiotic stress tolerance roles besides their roles in normal development. Determining the properties of sugar beet expansin, family members can help enable the cellulose hydrolysis mechanism and raise plant biomass. Elucidating expression profiles of the sugar beet expansin genes under variable stress conditions can support improving plant productivity. The results of the current study may also contribute to the deep understanding of sugar beet expansin genes in the future.

Genome-Wide Identification and Expression Patterns of Cucumber Invertases and Their Inhibitor Genes

Invertases and their inhibitors play important roles in sucrose metabolism, growth and development, signal transduction, and biotic and abiotic stress tolerance in many plant species. However, in cucumber, both the gene members and functions of invertase and its inhibitor families remain largely unclear. In this study, in comparison with the orthologues of Citrullus lanatus (watermelon), Cucumis melo (melon), and Arabidopsis thaliana (Arabidopsis), 12 invertase genes and 12 invertase inhibitor genes were identified from the genome of Cucumis sativus (cucumber). Among them, the 12 invertase genes were classified as 4 cell wall invertases, 6 cytoplasmic invertases, and 2 vacuolar invertases. Most invertase genes were conserved in cucumber, melon, and watermelon, with several duplicate genes in melon and watermelon. Transcriptome analysis distinguished these genes into various expression patterns, which included genes CsaV3_2G025540 and CsaV3_2G007220, which were significantly expressed in different tissues, organs, and development stages, and genes CsaV3_7G034730 and CsaV3_5G005910, which might be involved in biotic and abiotic stress. Six genes were further validated in cucumber based on quantitative real-time PCR (qRT-PCR), and three of them showed consistent expression patterns as revealed in the transcriptome. These results provide important information for further studies on the physiological functions of cucumber invertases (CSINVs) and their inhibitors (CSINHs).

A chromosome-scale Rhubarb (Rheum tanguticum) genome assembly provides insights into the evolution of anthraquinone biosynthesis

Rhubarb is the collective name for various perennial plants from the genus Rheum L. and the Polygonaceae family. They are one of the most ancient, commonly used, and important herbs in traditional Chinese medicine. Rhubarb is a major source of anthraquinones, but how they are synthesized remains largely unknown. Here, we generate a genome sequence assembly of one important medicinal rhubarb R. tanguticum at the chromosome level, with 2.76 Gb assembled into 11 chromosomes. The genome is shaped by two recent whole-genome duplication events and recent bursts of retrotransposons. Metabolic analyses show that the major anthraquinones are mainly synthesized in its roots. Transcriptomic analysis reveals a co-expression module with a high correlation to anthraquinone biosynthesis that includes key chalcone synthase genes. One CHS, four CYP450 and two BGL genes involved in secondary metabolism show significantly upregulated expression levels in roots compared with other tissues and clustered in the co-expression module, which implies that they may also act as candidate genes for anthraquinone biosynthesis. This study provides valuable insights into the genetic bases of anthraquinone biosynthesis that will facilitate improved breeding practices and agronomic properties for rhubarb in the future.

Combinatorial engineering of betalain biosynthesis pathway in yeast Saccharomyces cerevisiae

BACKGROUND

Betalains, comprising red-violet betacyanins and yellow-orange betaxanthins, are the hydrophilic vacuolar pigments that provide bright coloration to roots, fruits, and flowers of plants of the Caryophyllales order. Betanin extracted from red beets is permitted quantum satis as a natural red food colorant (E162). Due to antioxidant activity, betanin has potential health benefits.

RESULTS

We applied combinatorial engineering to find the optimal combination of a dozen tyrosine hydroxylase (TyH) and 4,5-dopa-estradiol-dioxygenase (DOD) variants. The best-engineered Saccharomyces cerevisiae strains produced over six-fold higher betaxanthins than previously reported. By genome-resequencing of these strains, we found out that two copies of DOD enzyme from Bougainvillea glabra together with TyH enzymes from Abronia nealleyi, Acleisanthes obtusa, and Cleretum bellidiforme were present in the three high-betaxanthin-producing isolates. Next, we expressed four variants of glucosyltransferases from Beta vulgaris for betanin biosynthesis. The highest titer of betanin (30.8 ± 0.14 mg/L after 48 h from 20 g/L glucose) was obtained when completing the biosynthesis pathway with UGT73A36 glucosyltransferase from Beta vulgaris. Finally, we investigated betalain transport in CEN.PK and S288C strains of Saccharomyces cerevisiae and identified a possible role of transporter genes QDR2 and APL1 in betanin transport.

CONCLUSIONS

This study shows the potential of combinatorial engineering of yeast cell factories for the biotechnological production of betanin.

Nuclear DNA segments homologous to mitochondrial DNA are obstacles for detecting heteroplasmy in sugar beet (Beta vulgaris L.)

Heteroplasmy, the coexistence of multiple mitochondrial DNA (mtDNA) sequences in a cell, is well documented in plants. Next-generation sequencing technology (NGS) has made it feasible to sequence entire genomes. Thus, NGS has the potential to detect heteroplasmy; however, the methods and pitfalls in heteroplasmy detection have not been fully investigated and identified. One obstacle for heteroplasmy detection is the sequence homology between mitochondrial-, plastid-, and nuclear DNA, of which the influence of nuclear DNA segments homologous to mtDNA (numt) need to be minimized. To detect heteroplasmy, we first excluded nuclear DNA sequences of sugar beet (Beta vulgaris) line EL10 from the sugar beet mtDNA sequence. NGS reads were obtained from single plants of sugar beet lines NK-195BRmm-O and NK-291BRmm-O and mapped to the unexcluded mtDNA regions. More than 1000 sites exhibited intra-individual polymorphism as detected by genome browsing analysis. We focused on a 309-bp region where 12 intra-individual polymorphic sites were closely linked to each other. Although the existence of DNA molecules having variant alleles at the 12 sites was confirmed by PCR amplification from NK-195BRmm-O and NK-291BRmm-O, these variants were not always called by six variant-calling programs, suggesting that these programs are inappropriate for intra-individual polymorphism detection. When we changed the nuclear DNA reference, a numt absent from EL10 was found to include the 309-bp region. Genetic segregation of an F2 population from NK-195BRmm-O x NK-291BRmm-O supported the numt origin of the variant alleles. Using four references, we found that numt detection exhibited reference dependency, and extreme polymorphism of numts exists among sugar beet lines. One of the identified numts absent from EL10 is also associated with another intra-individual polymorphic site in NK-195mm-O. Our data suggest that polymorphism among numts is unexpectedly high within sugar beets, leading to confusion about the true degree of heteroplasmy.

A chromosome-scale and haplotype-resolved genome assembly of carnation (Dianthus caryophyllus) based on high-fidelity sequencing

Dianthus caryophyllus is an economic species often considered excellent cut flowers and is suitable for bouquets and gardens. Here, we assembled the haplotype-resolved genome of D. caryophyllus 'Aili' at the chromosome level for the first time. The total lengths of the two assembled haplotypes of carnation were 584.88 Mb for haplotype genome 1 (hap1) and 578.78 Mb for haplotype genome 2 (hap2), respectively. We predicted a total of 44,098 and 42,425 protein-coding genes, respectively. The remarkable structure variation was identified between two haplotypes. Moreover, we identified 403.80 Mb of transposable elements (TEs) in hap1, which accounted for 69.34% of the genome. In contrast, hap2 had 402.70 Mb of TEs, representing 69.61% of the genome. Long terminal repeats were the predominant transposable elements. Phylogenetic analysis showed that the species differentiation time between carnation and gypsophila was estimated to be ~54.43 MYA. The unique gene families of carnation genomes were identified in 'Aili' and previously published 'Francesco' and 'Scarlet Queen'. The assembled and annotated haplotype-resolved D. caryophyllus genome not only promises to facilitate molecular biology studies but also contributes to genome-level evolutionary studies.

Salt priming induces low-temperature tolerance in sugar beet via xanthine metabolism

To understand the physiological mechanisms involved in xanthine metabolism during salt priming for improving low-temperature tolerance, salt priming (SP), xanthine dehydrogenase inhibitor (XOI), exogenous allantoin (EA), and back-supplemented EA (XOI + EA) treatments were given and the low-temperature tolerance of sugar beet was tested. Under low-temperature stress, salt priming promoted the growth of sugar beet leaves and increased the maximum quantum efficiency of PS II (Fv/Fm). However, during salt priming, either XOI or EA treatment alone increased the content of reactive oxygen species (ROS), such as superoxide anion and hydrogen peroxide, in the leaves under low-temperature stress. XOI treatment increased allantoinase activity with its gene (BvallB) expression under low-temperature stress. Compared to the XOI treatment, the EA treatment alone and the XOI + EA treatment increased the activities of antioxidant enzymes. At low temperatures, the sucrose content and the activity of key carbohydrate enzymes (AGPase, Cylnv, and FK) were significantly reduced by XOI compared to the changes under salt priming. XOI also stimulated the expression of protein phosphatase 2C and sucrose non-fermenting1-related protein kinase (BvSNRK2). The results of a correlation network analysis showed that BvallB was positively correlated with malondialdehyde, D-Fructose-6-phosphate, and D-Glucose-6-phosphate, and negatively correlated with BvPOX42, BvSNRK2, dehydroascorbate reductase, and catalase. These results suggested that salt-induced xanthine metabolism modulated ROS metabolism, photosynthetic carbon assimilation, and carbohydrate metabolism, thus enhancing low-temperature tolerance in sugar beet. Additionally, xanthine and allantoin were found to play key roles in plant stress resistance.

Genome sequencing reveals the genetic architecture of heterostyly and domestication history of common buckwheat

Common buckwheat, Fagopyrum esculentum, is an orphan crop domesticated in southwest China that exhibits heterostylous self-incompatibility. Here we present chromosome-scale assemblies of a self-compatible F. esculentum accession and a self-compatible wild relative, Fagopyrum homotropicum, together with the resequencing of 104 wild and cultivated F. esculentum accessions. Using these genomic data, we report the roles of transposable elements and whole-genome duplications in the evolution of Fagopyrum. In addition, we show that (1) the breakdown of heterostyly occurs through the disruption of a hemizygous gene jointly regulating the style length and female compatibility and (2) southeast Tibet was involved in common buckwheat domestication. Moreover, we obtained mutants conferring the waxy phenotype for the first time in buckwheat. These findings demonstrate the utility of our F. esculentum assembly as a reference genome and promise to accelerate buckwheat research and breeding.

A high-quality Bougainvillea genome provides new insights into evolutionary history and pigment biosynthetic pathways in the Caryophyllales

Bougainvillea is a perennial ornamental shrub that is highly regarded in ornamental horticulture around the world. However, the absence of genome data limits our understanding of the pathways involved in bract coloration and breeding. Here, we report a chromosome-level assembly of the giga-genome of Bougainvillea × buttiana 'Mrs Butt', a cultivar thought to be the origin of many other Bougainvillea cultivars. The assembled genome is ~5 Gb with a scaffold N50 of 151 756 278 bp and contains 86 572 genes which have undergone recent whole-genome duplication. We confirmed that multiple rounds of whole-genome multiplication have occurred in the evolutionary history of the Caryophyllales, reconstructed the relationship in the Caryophyllales at whole genome level, and found discordance between species and gene trees as the result of complex introgression events. We investigated betalain and anthocyanin biosynthetic pathways and found instances of independent evolutionary innovations in the nine different Caryophyllales species. To explore the potential formation mechanism of diverse bract colors in Bougainvillea, we analyzed the genes involved in betalain and anthocyanin biosynthesis and found extremely low expression of ANS and DFR genes in all cultivars, which may limit anthocyanin biosynthesis. Our findings indicate that the expression pattern of the betalain biosynthetic pathway did not directly correlate with bract color, and a higher expression level in the betalain biosynthetic pathway is required for colored bracts. This improved understanding of the correlation between gene expression and bract color allows plant breeding outcomes to be predicted with greater certainty.

Genetic diversity and genome-wide association study of 13 agronomic traits in 977 Beta vulgaris L. germplasms

BACKGROUND

Sugar beet (Beta vulgaris L.) is an economically essential sugar crop worldwide. Its agronomic traits are highly diverse and phenotypically plastic, influencing taproot yield and quality. The National Beet Medium-term Gene Bank in China maintains more than 1700 beet germplasms with diverse countries of origin. However, it lacks detailed genetic background associated with morphological variability and diversity.

RESULTS

Here, a comprehensive genome-wide association study (GWAS) of 13 agronomic traits was conducted in a panel of 977 sugar beet accessions. Almost all phenotypic traits exhibited wide genetic diversity and high coefficient of variation (CV). A total of 170,750 high-quality single-nucleotide polymorphisms (SNPs) were obtained using the genotyping-by-sequencing (GBS). Neighbour-joining phylogenetic analysis, principal component analysis, population structure and kinship showed no obvious relationships among these genotypes based on subgroups or regional sources. GWAS was carried out using a mixed linear model, and 159 significant associations were detected for these traits. Within the 25 kb linkage disequilibrium decay of the associated markers, NRT1/PTR FAMILY 6.3 (BVRB_5g097760); nudix hydrolase 15 (BVRB_8g182070) and TRANSPORT INHIBITOR RESPONSE 1 (BVRB_8g181550); transcription factor MYB77 (BVRB_2g023500); and ethylene-responsive transcription factor ERF014 (BVRB_1g000090) were predicted to be strongly associated with the taproot traits of root groove depth (RGD); root shape (RS); crown size (CS); and flesh colour (FC), respectively. For the aboveground traits, UDP-glycosyltransferase 79B6 (BVRB_9g223780) and NAC domain-containing protein 7 (BVRB_5g097990); F-box protein At1g10780 (BVRB_6g140760); phosphate transporter PHO1 (BVRB_3g048660); F-box protein CPR1 (BVRB_8g181140); and transcription factor MYB77 (BVRB_2g023500) and alcohol acyltransferase 9 (BVRB_2g023460) might be associated with the hypocotyl colour (HC); plant type (PT); petiole length (PL); cotyledon size (C); and fascicled leaf type (FLT) of sugar beet, respectively. AP-2 complex subunit mu (BVRB_5g106130), trihelix transcription factor ASIL2 (BVRB_2g041790) and late embryogenesis abundant protein 18 (BVRB_5g106150) might be involved in pollen quantity (PQ) variation. The candidate genes extensively participated in hormone response, nitrogen and phosphorus transportation, secondary metabolism, fertilization and embryo maturation.

CONCLUSIONS

The genetic basis of agronomical traits is complicated in heterozygous diploid sugar beet. The putative valuable genes found in this study will help further elucidate the molecular mechanism of each phenotypic trait for beet breeding.

Unique Features of the m6A Methylome and Its Response to Salt Stress in the Roots of Sugar Beet (Beta vulgaris)

Salt is one of the most important environmental factors in crop growth and development. N⁶-methyladenosine (m⁶A) is an epigenetic modification that regulates plant-environment interaction at transcriptional and translational levels. Sugar beet is a salt-tolerant sugar-yielding crop, but how m⁶A modification affects its response to salt stress remains unknown. In this study, m⁶A-seq was used to explore the role of m⁶A modification in response to salt stress in sugar beet (Beta vulgaris). Transcriptome-wide m⁶A methylation profiles and physiological responses to high salinity were investigated in beet roots. After treatment with 300 mM NaCl, the activities of peroxidase and catalase, the root activity, and the contents of Na⁺, K⁺, and Ca²⁺ in the roots were significantly affected by salt stress. Compared with the control plants, 6904 differentially expressed genes (DEGs) and 566 differentially methylated peaks (DMPs) were identified. Association analysis revealed that 243 DEGs contained DMP, and 80% of these DEGs had expression patterns that were negatively correlated with the extent of m⁶A modification. Further analysis verified that m⁶A methylation may regulate the expression of some genes by controlling their mRNA stability. Functional analysis revealed that m⁶A modifications primarily affect the expression of genes involved in energy metabolism, transport, signal transduction, transcription factors, and cell wall organization. This study provides evidence that a post-transcriptional regulatory mechanism mediates gene expression during salt stress by affecting the stability of mRNA in the root.

The genome of the glasshouse plant noble rhubarb (Rheum nobile) provides a window into alpine adaptation

Glasshouse plants are species that trap warmth via specialized morphology and physiology, mimicking a human glasshouse. In the Himalayan alpine region, the highly specialized glasshouse morphology has independently evolved in distinct lineages to adapt to intensive UV radiation and low temperature. Here we demonstrate that the glasshouse structure - specialized cauline leaves - is highly effective in absorbing UV light but transmitting visible and infrared light, creating an optimal microclimate for the development of reproductive organs. We reveal that this glasshouse syndrome has evolved at least three times independently in the rhubarb genus Rheum. We report the genome sequence of the flagship glasshouse plant Rheum nobile and identify key genetic network modules in association with the morphological transition to specialized glasshouse leaves, including active secondary cell wall biogenesis, upregulated cuticular cutin biosynthesis, and suppression of photosynthesis and terpenoid biosynthesis. The distinct cell wall organization and cuticle development might be important for the specialized optical property of glasshouse leaves. We also find that the expansion of LTRs has likely played an important role in noble rhubarb adaptation to high elevation environments. Our study will enable additional comparative analyses to identify the genetic basis underlying the convergent occurrence of glasshouse syndrome.

Salt and drought stress-mitigating approaches in sugar beet (Beta vulgaris L.) to improve its performance and yield

MAIN CONCLUSION

Although sugar beet is a salt- and drought-tolerant crop, high salinity, and water deprivation significantly reduce its yield and growth. Several reports have demonstrated stress tolerance enhancement through stress-mitigating strategies including the exogenous application of osmolytes or metabolites, nanoparticles, seed treatments, breeding salt/drought-tolerant varieties. These approaches would assist in achieving sustainable yields despite global climatic changes. Sugar beet (Beta vulgaris L.) is an economically vital crop for ~ 30% of world sugar production. They also provide essential raw materials for bioethanol, animal fodder, pulp, pectin, and functional food-related industries. Due to fewer irrigation water requirements and shorter regeneration time than sugarcane, beet cultivation is spreading to subtropical climates from temperate climates. However, beet varieties from different geographical locations display different stress tolerance levels. Although sugar beet can endure moderate exposure to various abiotic stresses, including high salinity and drought, prolonged exposure to salt and drought stress causes a significant decrease in crop yield and production. Hence, plant biologists and agronomists have devised several strategies to mitigate the stress-induced damage to sugar beet cultivation. Recently, several studies substantiated that the exogenous application of osmolytes or metabolite substances can help plants overcome injuries induced by salt or drought stress. Furthermore, these compounds likely elicit different physio-biochemical impacts, including improving nutrient/ionic homeostasis, photosynthetic efficiency, strengthening defense response, and water status improvement under various abiotic stress conditions. In the current review, we compiled different stress-mitigating agricultural strategies, prospects, and future experiments that can secure sustainable yields for sugar beets despite high saline or drought conditions.

Waterlogging stress alters the structure of sugar beet rhizosphere microbial community structure and recruiting potentially beneficial bacterial

Waterlogging has been shown to have a significant inhibitory effect on plant growth. However, the response mechanisms of the soil environment of sugar beet seedlings under waterlogging conditions still need to be fully understood. This study aimed to investigate the effects of waterlogging treatments on the content of effective nutrients and the microbial communities in the rhizosphere and non-rhizosphere using high-throughput sequencing. We set up waterlogging and non-waterlogging treatments, sampled sugar beet seedlings after 10 days of waterlogging, determined the effective soil nutrients in the rhizosphere and non-rhizosphere of the plants, and analyzed the differences in microbial diversity at ten days of waterlogging. The results showed that waterlogging significantly affected available potassium (AK) content. The Ak content of waterlogged soil was significantly higher than that of non-waterlogged soil. Waterlogging caused no significant difference in available nitrogen (AN) content and pH. Moreover, the plant growth-promoting bacteria Pseudomonas was significantly enriched in sugar beet waterlogged rhizospheres compared with the non-waterlogged ones. Similarly, the harmful fungi Gibellulopsis and Alternaria were enriched in sugar beet non-waterlogged rhizosphere. The network analysis revealed that waterlogging built a less complex root-microbial network than non-waterlogging. These findings implied that sugar beets subjected to waterlogging stress were enriched with beneficial microorganisms in the rhizosphere, potentially alleviating the stress.

Systematic investigation of the R2R3-MYB gene family in Aquilaria sinensis reveals a transcriptional repressor AsMYB054 involved in 2-(2-phenylethyl)chromone biosynthesis

Trees in the genus Aquilaria produce agarwood, a valuable resin used in medicine, perfumes, and incense. 2-(2-Phenethyl)chromones (PECs) are characteristic components of agarwood; however, molecular mechanisms underlying PEC biosynthesis and regulation remain largely unknown. The R2R3-MYB transcription factors play important regulatory roles in the biosynthesis of various secondary metabolites. In this study, 101 R2R3-MYB genes in Aquilaria sinensis were systematically identified and analyzed at the genome-wide level. Transcriptomic analysis revealed that 19 R2R3-MYB genes were significantly regulated by an agarwood inducer, and showed significant correlations with PEC accumulation. Expression and evolutionary analyses revealed that AsMYB054, a subgroup 4 R2R3-MYB, was negatively correlated with PEC accumulation. AsMYB054 was located in the nucleus and functioned as a transcriptional repressor. Moreover, AsMYB054 could bind to the promoters of the PEC biosynthesis related genes AsPKS02 and AsPKS09, and inhibit their transcriptional activity. These findings suggested that AsMYB054 functions as a negative regulator of PEC biosynthesis via the inhibition of AsPKS02 and AsPKS09 in A. sinensis. Our results provide a comprehensive understanding of the R2R3-MYB subfamily in A. sinensis and lay a foundation for further functional analyses of R2R3-MYB genes in PEC biosynthesis.

Proteomics Approach to Differentiate Protein Extraction Methods in Sugar Beet Leaves

Interest in alternative plant-based protein sources is continuously growing. Sugar beet leaves have the potential to satisfy that demand due to their high protein content. They are considered as agricultural waste and utilizing them as protein sources can bring them back to the food chain. In this study, isoelectric-point-precipitation, heat-coagulation, ammonium-sulfate precipitation, high-pressure-assisted isoelectric-point precipitation, and high-pressure-assisted heat coagulation methods were used to extract proteins from sugar beet leaves. A mass spectrometry-based proteomic approach was used for comprehensive protein characterization. The analyses yielded 817 proteins, the most comprehensive protein profile on sugar beet leaves to date. Although the total protein contents were comparable, there was a significant difference between the methods for low-abundance proteins. High-pressure-assisted methods showed elevated levels of proteins predominantly located in the chloroplast. Here we showed for the first time that the extraction/precipitation methods may result in different protein profiles that potentially affect the physical and nutritional properties of functional products.

Genomic variation in the genus Beta based on 656 sequenced beet genomes

Cultivated beets (Beta vulgaris ssp. vulgaris) constitute important crop plants, in particular sugar beet as an indispensable source of sucrose. Several species of wild beets of the genus Beta with distribution along the European Atlantic coast, Macaronesia, and throughout the Mediterranean area exist. Thorough characterization of beet genomes is required for straightforward access to genes promoting genetic resistance against biotic and abiotic stress. Analysing short-read data of 656 sequenced beet genomes, we identified 10 million variant positions in comparison to the sugar beet reference genome RefBeet-1.2. The main groups of species and subspecies were distinguishable based on shared variation, and the separation of sea beets (Beta vulgaris ssp. maritima) into a Mediterranean and an Atlantic subgroup as suggested by previous studies could be confirmed. Complementary approaches of variant-based clustering were employed based on PCA, genotype likelihoods, tree calculations, and admixture analysis. Outliers suggested the occurrence of inter(sub)specific hybridisation, independently confirmed by different analyses. Screens for regions under artificial selection in the sugar beet genome identified 15 Mbp of the genome as variation-poor, enriched for genes involved in shoot system development, stress response, and carbohydrate metabolism. The resources presented herein will be valuable for crop improvement and wild species monitoring and conservation efforts, and for studies on beet genealogy, population structure and population dynamics. Our study provides a wealth of data for in-depth analyses of further aspects of the beet genome towards a thorough understanding of the biology of this important complex of a crop species and its wild relatives.

The first chromosome-level Fallopia multiflora genome assembly provides insights into stilbene biosynthesis

Fallopia multiflora (Thunb.) Harald, a vine belonging to the Polygonaceae family, is used in traditional medicine. The stilbenes contained in it have significant pharmacological activities in anti-oxidation and anti-aging. This study describes the assembly of the F. multiflora genome and presents its chromosome-level genome sequence containing 1.46 gigabases of data (with a contig N50 of 1.97 megabases), 1.44 gigabases of which was assigned to 11 pseudochromosomes. Comparative genomics confirmed that F. multiflora shared a whole-genome duplication event with Tartary buckwheat and then underwent different transposon evolution after separation. Combining genomics, transcriptomics, and metabolomics data to map a network of associated genes and metabolites, we identified two FmRS genes responsible for the catalysis of one molecule of p-coumaroyl-CoA and three molecules of malonyl-CoA to resveratrol in F. multiflora. These findings not only serve as the basis for revealing the stilbene biosynthetic pathway but will also contribute to the development of tools for increasing the production of bioactive stilbenes through molecular breeding in plants or metabolic engineering in microbes. Moreover, the reference genome of F. multiflora is a useful addition to the genomes of the Polygonaceae family.

Cation diffusion facilitator proteins of Beta vulgaris reveal diversity of metal handling in dicotyledons

Manganese (Mn), iron (Fe), and zinc (Zn) are essential for diverse processes in plants, but their availability is often limiting or excessive. Cation diffusion facilitator (CDF) proteins have been implicated in the allocation of those metals in plants, whereby most of our mechanistic understanding has been obtained in Arabidopsis. It is unclear to what extent this can be generalized to other dicots. We characterized all CDFs/metal tolerance proteins of sugar beet (Beta vulgaris spp. vulgaris), which is phylogenetically distant from Arabidopsis. Analysis of subcellular localization, substrate selectivities, and transcriptional regulation upon exposure to metal deficiencies and toxicities revealed unexpected deviations from their Arabidopsis counterparts. Localization and selectivity of some members were modulated by alternative splicing. Notably, unlike in Arabidopsis, Mn- and Zn-sequestrating members were not induced in Fe-deficient roots, pointing to differences in the Fe acquisition machinery. This was supported by low Zn and Mn accumulation under Fe deficiency and a strikingly increased Fe accumulation under Mn and Zn excess, coinciding with an induction of BvIRT1. High Zn load caused a massive upregulation of Zn-BvMTPs. The results suggest that the employment of the CDF toolbox is highly diverse amongst dicots, which questions the general applicability of metal homeostasis models derived from Arabidopsis.

Putting hornets on the genomic map

Hornets are the largest of the social wasps, and are important regulators of insect populations in their native ranges. Hornets are also very successful as invasive species, with often devastating economic, ecological and societal effects. Understanding why these wasps are such successful invaders is critical to managing future introductions and minimising impact on native biodiversity. Critical to the management toolkit is a comprehensive genomic resource for these insects. Here we provide the annotated genomes for two hornets, Vespa crabro and Vespa velutina. We compare their genomes with those of other social Hymenoptera, including the northern giant hornet Vespa mandarinia. The three hornet genomes show evidence of selection pressure on genes associated with reproduction, which might facilitate the transition into invasive ranges. Vespa crabro has experienced positive selection on the highest number of genes, including those putatively associated with molecular binding and olfactory systems. Caste-specific brain transcriptomic analysis also revealed 133 differentially expressed genes, some of which are associated with olfactory functions. This report provides a spring-board for advancing our understanding of the evolution and ecology of hornets, and opens up opportunities for using molecular methods in the future management of both native and invasive populations of these over-looked insects.

DNA methylation signatures of duplicate gene evolution in angiosperms

Gene duplication is a source of evolutionary novelty. DNA methylation may play a role in the evolution of duplicate genes (paralogs) through its association with gene expression. While this relationship has been examined to varying extents in a few individual species, the generalizability of these results at either a broad phylogenetic scale with species of differing duplication histories or across a population remains unknown. We applied a comparative epigenomics approach to 43 angiosperm species across the phylogeny and a population of 928 Arabidopsis (Arabidopsis thaliana) accessions, examining the association of DNA methylation with paralog evolution. Genic DNA methylation was differentially associated with duplication type, the age of duplication, sequence evolution, and gene expression. Whole genome duplicates were typically enriched for CG-only gene-body methylated or unmethylated genes, while single-gene duplications were typically enriched for non-CG methylated or unmethylated genes. Non-CG methylation, in particular, was characteristic of more recent single-gene duplicates. Core angiosperm gene families differentiated into those which preferentially retain paralogs and 'duplication-resistant' families, which convergently reverted to singletons following duplication. Duplication-resistant families that still have paralogous copies were, uncharacteristically for core angiosperm genes, enriched for non-CG methylation. Non-CG methylated paralogs had higher rates of sequence evolution, higher frequency of presence-absence variation, and more limited expression. This suggests that silencing by non-CG methylation may be important to maintaining dosage following duplication and be a precursor to fractionation. Our results indicate that genic methylation marks differing evolutionary trajectories and fates between paralogous genes and have a role in maintaining dosage following duplication.

Genome-wide identification and expression analysis of SUT gene family members in sugar beet (Beta vulgaris L.)

Sucrose transporters (SUTs) play an important role in the transmembrane transport and distribution of sucrose, and their activity has an important impact on plant growth and crop yield. In this study, the SUT gene family was identified in the whole beet genome using bioinformatics methods, and gene characteristics, subcellular localization prediction, phylogenetic evolution, promoter cis-elements and expression patterns were systematically analyzed. A total of 9 SUT gene family members were identified from in beet genome and divided into 3 different groups (group 1, group 2, and Group 3), which were unevenly distributed on 4 chromosomes. Most SUT family members contained photoresponsive and hormone-regulated response elements. Subcellular localization prediction showed that the BvSUT genes are all located in the inner membrane, and most of the terms identified through GO enrichment analysis are classified as "membrane" related. The results of RT-qPCR showed that the expression level of the BvSUT gene was significantly higher in the tuber enlargement stage (100-140 d) than in other stages. This study is the first to analyze the BvSUT gene family in sugar beet, and it provides a theoretical basis for the functional exploration and application of SUT genes in crop improvement, especially in sugar crops.

Insights into physiological and molecular mechanisms underlying efficient utilization of boron in different boron efficient Beta vulgaris L. varieties

Boron (B) deficiency and consequent limitation of plant yield and quality, particularly of sugar beet (Beta vulgaris L.) has emerged as a maior problem,which is exacerbating due to cultivar dependent variability in B deficiency tolerance. Pertinently, the current study was designed to elucidate the physiological and molecular mechanisms of B deficiency tolerance of sugar beet varieties KWS1197 (B-efficient variety) and KWS0143 (B-inefficient variety). A hydroponic experiment was conducted employing two B levels B0.1 (0.1 μM L^-1 H₃BO₃, deficiency) and B50 (50 μM L^-1 H₃BO₃, adequacy). Boron deficiency greatly inhibited root elongation and dry matter accumulation; however, formation of lateral roots stimulated and average root diameter was increased. Results exhibited that by up-regulating the expression of NIP5-1, NIP6-1, and BOR2, and suppressing the expression of BOR4, cultivar KWS1197, in contrast to KWS0143, managed to transfer sufficient amount of B to the aboveground plant parts, facilitating its effective absorption and utilization. Accumulation of malondialdehyde (MDA) and reactive oxygen species (ROS) was also mellowed in KWS1197, as well as the oxidative damage to root cells via preservation of the antioxidant enzyme system. Additionally, the expression of essential enzymes for biosynthesis of phytohormone (PYR/PYL) and lignin (COMT, POX, and CCoAOMT) were found to be highly up-regulated in KWS1197. Deductively, through effective B absorption and transportation, balanced nutrient accumulation, and an activated antioxidant enzyme system, B-efficient cultivars may cope with B deficiency while retaining a superior cellular structure to enable root development.

Insights into the differentiation and adaptation within Circaeasteraceae from Circaeaster agrestis genome sequencing and resequencing

Circaeaster agrestis and Kingdonia uniflora are sister species that reproduce sexually and mainly asexually respectively, providing a good system for comparative genome evolution between taxa with different reproductive models. Comparative genome analyses revealed the two species have similar genome size, but C. agrestis encodes many more genes. The gene families specific to C. agrestis show significant enrichment of genes associated with defense response, while those gene families specific to K. uniflora are enriched in genes regulating root system development. Collinearity analyses revealed C. agrestis experienced two rounds of whole-genome duplication. Fst outlier test across 25 C. agrestis populations uncovered a close inter-relationship between abiotic stress and genetic variability. Genetic feature comparisons showed K. uniflora presents much higher genome heterozygosity, transposable element load, linkage disequilibrium degree, and π_N/π_S ratio. This study provides new insights into understanding the genetic differentiation and adaptation within ancient lineages characterized by multiple reproductive models.

A comprehensive and conceptual overview of omics-based approaches for enhancing the resilience of vegetable crops against abiotic stresses

Abiotic stresses adversely affect the productivity and production of vegetable crops. The increasing number of crop genomes that have been sequenced or re-sequenced provides a set of computationally anticipated abiotic stress-related responsive genes on which further research may be focused. Knowledge of omics approaches and other advanced molecular tools have all been employed to understand the complex biology of these abiotic stresses. A vegetable can be defined as any component of a plant that is eaten for food. These plant parts may be celery stems, spinach leaves, radish roots, potato tubers, garlic bulbs, immature cauliflower flowers, cucumber fruits, and pea seeds. Abiotic stresses, such as deficient or excessive water, high temperature, cold, salinity, oxidative, heavy metals, and osmotic stress, are responsible for the adverse activity in plants and, ultimately major concern for decreasing yield in many vegetable crops. At the morphological level, altered leaf, shoot and root growth, altered life cycle duration and fewer or smaller organs can be observed. Likewise different physiological and biochemical/molecular processes are also affected in response to these abiotic stresses. In order to adapt and survive in a variety of stressful situations, plants have evolved physiological, biochemical, and molecular response mechanisms. A comprehensive understanding of the vegetable's response to different abiotic stresses and the identification of tolerant genotypes are essential to strengthening each vegetable's breeding program. The advances in genomics and next-generation sequencing have enabled the sequencing of many plant genomes over the last twenty years. A combination of modern genomics (MAS, GWAS, genomic selection, transgenic breeding, and gene editing), transcriptomics, and proteomics along with next-generation sequencing provides an array of new powerful approaches to the study of vegetable crops. This review examines the overall impact of major abiotic stresses on vegetables, adaptive mechanisms and functional genomic, transcriptomic, and proteomic processes used by researchers to minimize these challenges. The current status of genomics technologies for developing adaptable vegetable cultivars that will perform better in future climates is also examined.

Tartary Buckwheat Grain as a Source of Bioactive Compounds in Husked Groats

Tartary buckwheat (Fagopyrum tataricum Gaertn.) originates in mountain regions of Western China, and is cultivated in China, Bhutan, Northern India, Nepal, and Central Europe. The content of flavonoids in Tartary buckwheat grain and groats is much higher than in common buckwheat (Fagopyrum esculentum Moench), and depends on ecological conditions, such as UV-B radiation. Buckwheat intake has preventative effects in chronic diseases, such as cardiovascular diseases, diabetes, and obesity, due to its content of bioactive substances. The main bioactive compounds in Tartary buckwheat groats are flavonoids (rutin and quercetin). There are differences in the bioactivities of buckwheat groats obtained using different husking technologies, based on husking raw or pretreated grain. Husking hydrothermally pretreated grain is among the traditional ways of consuming buckwheat in Europe and some parts of China and Japan. During hydrothermal and other processing of Tartary buckwheat grain, a part of rutin is transformed to quercetin, the degradation product of rutin. By adjusting the humidity of materials and the processing temperature, it is possible to regulate the degree of conversion of rutin to quercetin. Rutin is degraded to quercetin in Tartary buckwheat grain due to the enzyme rutinosidase. The high-temperature treatment of wet Tartary buckwheat grain is able to prevent the transformation of rutin to quercetin.