Oxylipin signaling in salt-stressed soybean is modulated by ligand-dependent interaction of Class II acyl-CoA-binding proteins with lipoxygenase.

Plant lipoxygenases (LOXs) oxygenate linoleic and linolenic acids, creating hydroperoxy derivatives, and from these, jasmonates and other oxylipins are derived. Despite the importance of oxylipin signaling, its activation mechanism remains largely unknown. Here, we show that soybean ACYL-COA-BINDING PROTEIN3 (ACBP3) and ACBP4, two Class II acyl-CoA-binding proteins, suppressed activity of the vegetative LOX homolog VLXB by sequestering it at the endoplasmic reticulum. The ACBP4-VLXB interaction was facilitated by linoleoyl-CoA and linolenoyl-CoA, which competed with phosphatidic acid (PA) for ACBP4 binding. In salt-stressed roots, alternative splicing produced ACBP variants incapable of VLXB interaction. Overexpression of the variants enhanced LOX activity and salt tolerance in Arabidopsis and soybean hairy roots, whereas overexpressors of the native forms exhibited reciprocal phenotypes. Consistently, the differential alternative splicing pattern in two soybean genotypes coincided with their difference in salt-induced lipid peroxidation. Salt-treated soybean roots were enriched in C32:0-PA species that showed high affinity to Class II ACBPs. We conclude that PA signaling and alternative splicing suppress ligand-dependent interaction of Class II ACBPs with VLXB, thereby triggering lipid peroxidation during salt stress. Hence, our findings unveil a dual mechanism that initiates the onset of oxylipin signaling in the salinity response.

A natural non-synonymous single nucleotide polymorphism in GmbHLH113 negates its inhibitory effect on root hair elongation in soybean.

Root hair length (RHL) is an important character that affects nutrient acquisition in plants. The regulatory network in soybean controlling RHL is yet to be fully understood. In this study, we identified a quantitative trait locus (QTL) regulating RHL. One candidate causal gene in this QTL (GmbHLH113), preferentially expressed in root hairs, was annotated as encoding a basic helix-loop-helix transcription factor. In wild soybeans, the allelic type of GmbHLH113 with a glycine in the 13th residue, which was associated with a reduction in RHL, was shown to localize in the nucleus and activate gene transcription. Another allelic type with a single nucleotide polymorphism that resulted in a glutamate in the 13th residue is fixed in cultivated soybeans, and it lost the ability to localize to the nucleus or negatively regulate RHL. The ectopic expression of GmbHLH113 from W05 in Arabidopsis root hairs resulted in shorter RHL and reduced phosphorus (P) accumulation in shoots. Hence, a loss-of-function allele in cultivated soybeans might have been selected during domestication due to its association with a longer RHL and improved nutrient acquisition.

Developing an SNP dataset for efficiently evaluating soybean germplasm resources using the genome sequencing data of 3,661 soybean accessions.

BACKGROUND: Single nucleotide polymorphism (SNP) markers play significant roles in accelerating breeding and basic crop research. Several soybean SNP panels have been developed. However, there is still a lack of SNP panels for differentiating between wild and cultivated populations, as well as for detecting polymorphisms within both wild and cultivated populations. RESULTS: This study utilized publicly available resequencing data from over 3,000 soybean accessions to identify differentiating and highly conserved SNP and insertion/deletion (InDel) markers between wild and cultivated soybean populations. Additionally, a naturally occurring mutant gene library was constructed by analyzing large-effect SNPs and InDels in the population. CONCLUSION: The markers obtained in this study are associated with numerous genes governing agronomic traits, thus facilitating the evaluation of soybean germplasms and the efficient differentiation between wild and cultivated soybeans. The natural mutant gene library permits the quick identification of individuals with natural mutations in functional genes, providing convenience for accelerating soybean breeding using reverse genetics.

Elucidating the ecophysiology of soybean pod-sucking stinkbug Riptortus pedestris (Hemiptera: Alydidae) based on de novo genome assembly and transcriptome analysis.

Food security is important for the ever-growing global population. Soybean, Glycine max (L.) Merr., is cultivated worldwide providing a key source of food, protein and oil. Hence, it is imperative to maintain or to increase its yield under different conditions including challenges caused by abiotic and biotic stresses. In recent years, the soybean pod-sucking stinkbug Riptortus pedestris has emerged as an important agricultural insect pest in East, South and Southeast Asia. Here, we present a genomics resource for R. pedestris including its genome assembly, messenger RNA (mRNA) and microRNA (miRNA) transcriptomes at different developmental stages and from different organs. As insect hormone biosynthesis genes (genes involved in metamorphosis) and their regulators such as miRNAs are potential targets for pest control, we analyzed the sesquiterpenoid (juvenile) and ecdysteroid (molting) hormone biosynthesis pathway genes including their miRNAs and relevant neuropeptides. Temporal gene expression changes of these insect hormone biosynthesis pathways were observed at different developmental stages. Similarly, a diet-specific response in gene expression was also observed in both head and salivary glands. Furthermore, we observed that microRNAs (bantam, miR-14, miR-316, and miR-263) of R. pedestris fed with different types of soybeans were differentially expressed in the salivary glands indicating a diet-specific response. Interestingly, the opposite arms of miR-281 (-5p and -3p), a miRNA involved in regulating development, were predicted to target Hmgs genes of R. pedestris and soybean, respectively. These observations among others highlight stinkbug's responses as a function of its interaction with soybean. In brief, the results of this study not only present salient findings that could be of potential use in pest management and mitigation but also provide an invaluable resource for R. pedestris as an insect model to facilitate studies on plant-pest interactions.

Fast-forward breeding for a food-secure world.

Crop production systems need to expand their outputs sustainably to feed a burgeoning human population. Advances in genome sequencing technologies combined with efficient trait mapping procedures accelerate the availability of beneficial alleles for breeding and research. Enhanced interoperability between different omics and phenotyping platforms, leveraged by evolving machine learning tools, will help provide mechanistic explanations for complex plant traits. Targeted and rapid assembly of beneficial alleles using optimized breeding strategies and precise genome editing techniques could deliver ideal crops for the future. Realizing desired productivity gains in the field is imperative for securing an adequate future food supply for 10 billion people.

From trade-off to synergy: microbial insights into enhancing plant growth and immunity.

The reduction in crop yield caused by pathogens and pests presents a significant challenge to global food security. Genetic engineering, which aims to bolster plant defence mechanisms, emerges as a cost-effective solution for disease control. However, this approach often incurs a growth penalty, known as the growth-defence trade-off. The precise molecular mechanisms governing this phenomenon are still not completely understood, but they generally fall under two main hypotheses: a "passive" redistribution of metabolic resources, or an "active" regulatory choice to optimize plant fitness. Despite the knowledge gaps, considerable practical endeavours are in the process of disentangling growth from defence. The plant microbiome, encompassing both above- and below-ground components, plays a pivotal role in fostering plant growth and resilience to stresses. There is increasing evidence which indicates that plants maintain intimate associations with diverse, specifically selected microbial communities. Meta-analyses have unveiled well-coordinated, two-way communications between plant shoots and roots, showcasing the capacity of plants to actively manage their microbiota for balancing growth with immunity, especially in response to pathogen incursions. This review centers on successes in making use of specific root-associated microbes to mitigate the growth-defence trade-off, emphasizing pivotal advancements in unravelling the mechanisms behind plant growth and defence. These findings illuminate promising avenues for future research and practical applications.

The genome and sex-dependent responses to temperature in the common yellow butterfly, Eurema hecabe.

BACKGROUND: Lepidoptera (butterflies and moths) is one of the most geographically widespread insect orders in the world, and its species play important and diverse ecological and applied roles. Climate change is one of the biggest challenges to biodiversity this century, and lepidopterans are vulnerable to climate change. Temperature-dependent gene expression differences are of relevance under the ongoing climate crisis. However, little is known about how climate affects gene expression in lepidopterans and the ecological consequences of this, particularly with respect to genes with biased expression in one of the sexes. The common yellow butterfly, Eurema hecabe (Family Pieridae), is one of the most geographically widespread lepidopterans that can be found in Asia, Africa, and Australia. Nevertheless, what temperature-dependent effects there may be and whether the effects differ between the sexes remain largely unexplored. RESULTS: Here, we generated high-quality genomic resources for E. hecabe along with transcriptomes from eight developmental stages. Male and female butterflies were subjected to varying temperatures to assess sex-specific gene expression responses through mRNA and microRNA transcriptomics. We find that there are more temperature-dependent sex-biased genes in females than males, including genes that are involved in a range of biologically important functions, highlighting potential ecological impacts of increased temperatures. Further, by considering available butterfly data on sex-biased gene expression in a comparative genomic framework, we find that the pattern of sex-biased gene expression identified in E. hecabe is highly species-specific, rather than conserved across butterfly species, suggesting that sex-biased gene expression responses to climate change are complex in butterflies. CONCLUSIONS: Our study lays the foundation for further understanding of differential responses to environmental stress in a widespread lepidopteran model and demonstrates the potential complexity of sex-specific responses of lepidopterans to climate change.

Priming-induced alterations in histone modifications modulate transcriptional responses in soybean under salt stress.

Plants that have experienced certain abiotic stress may gain tolerance to a similar stress in subsequent exposure. This phenomenon, called priming, was observed here in soybean (Glycine max) seedlings exposed to salt stress. Time-course transcriptomic profiles revealed distinctively different transcriptional responses in the primed seedlings from those in the non-primed seedlings under high salinity stress, indicating a stress response strategy of repressing unhelpful biotic stress responses and focusing on the promotion of those responses important for salt tolerance. To identify histone marks altered by the priming salinity treatment, a genome-wide profiling of histone 3 lysine 4 dimethylation (H3K4me2), H3K4me3, and histone 3 lysine 9 acetylation (H3K9ac) was performed. Our integrative analyses revealed that priming induced drastic alterations in these histone marks, which coordinately modified the stress response, ion homeostasis, and cell wall modification. Furthermore, transcriptional network analyses unveiled epigenetically modified networks which mediate the strategic downregulation of defense responses. Altering the histone acetylation status using a chemical inhibitor could elicit the priming-like transcriptional responses in non-primed seedlings, confirming the importance of histone marks in forming the priming response.

ShinySyn: a Shiny/R application for the interactive visualization and integration of macro- and micro-synteny data.

MOTIVATION: Synteny analysis is a widely used framework in comparative genomics studies, which provides valuable information to reveal chromosome collinearity in both intra-species and inter-species. Most analysis pipelines, however, are command line-based, making it challenging for biologists to run the algorithms and visualize the results. Existing visualization tools either provide static plots or can only be run on web-based servers and lack efficient visualization methods for associating macro-synteny blocks with individual gene pairs in a micro-synteny region. RESULTS: We developed ShinySyn, a Shiny/R application built on the MCscan framework that provides an easy-to-use graphic interface for synteny analyses without requiring any programming skills, to reduce technical barriers. ShinySyn not only provides interactive visualization for macro-synteny, micro-synteny and genome-level dot views, but it also creates an intuitive representation with a dynamic zooming feature from macro-synteny to individual homologous genes. AVAILABILITY AND IMPLEMENTATION: The source code and installation instructions for ShinySyn can be accessed via https://github.com/obenno/ShinySyn. A pre-built docker image is also available at https://hub.docker.com/r/obenno/shinysyn. The application can be used locally or seamlessly integrated into any Shiny application server.

MicroRNA 4407 modulates nodulation in soybean by repressing a root-specific ISOPENTENYLTRANSFERASE (GmIPT3).

MicroRNAs (miRNAs) are important regulators of plant biological processes, including soybean nodulation. One miRNA, miR4407, was identified in soybean roots and nodules. However, the function of miR4407 in soybean is still unknown. MiR4407, unique to soybean, positively regulates lateral root emergence and root structures and represses a root-specific ISOPENTENYLTRANSFERASE (GmIPT3). By altering the expression of miR4407 and GmIPT3, we investigated the role of miR4407 in lateral root and nodule development. Both miR4407 and GmIPT3 are expressed in the inner root cortex and nodule primordia. Upon rhizobial inoculation, miR4407 was downregulated while GmIPT3 was upregulated. Overexpressing miR4407 reduced the number of nodules in transgenic soybean hairy roots while overexpressing the wild-type GmIPT3 or a miR4407-resistant GmIPT3 mutant (mGmIPT3) significantly increased the nodule number. The mechanism of miR4407 and GmIPT3 functions was also linked to autoregulation of nodulation (AON), where miR4407 overexpression repressed miR172c and activated its target, GmNNC1, turning on AON. Exogenous CK mimicked the effects of GmIPT3 overexpression on miR172c, supporting the notion that GmIPT3 regulates nodulation by enhancing root-derived CK. Overall, our data revealed a new miRNA-mediated regulatory mechanism of nodulation in soybean. MiR4407 showed a dual role in lateral root and nodule development.

Non-specific LIPID TRANSFER PROTEIN 1 enhances immunity against tobacco mosaic virus in Nicotiana benthamiana.

Plant non-specific lipid transfer proteins (nsLTPs) are small, cysteine-rich proteins that play significant roles in biotic and abiotic stress responses; however, the molecular mechanism of their functions against viral infections remains unclear. In this study, we employed virus-induced gene-silencing and transgenic overexpression to functionally analyse a type-I nsLTP in Nicotiana benthamiana, NbLTP1, in the immunity response against tobacco mosaic virus (TMV). NbLTP1 was inducible by TMV infection, and its silencing increased TMV-induced oxidative damage and the production of reactive oxygen species (ROS), compromised local and systemic resistance to TMV, and inactivated the biosynthesis of salicylic acid (SA) and its downstream signaling pathway. The effects of NbLTP1-silencing were partially restored by application of exogenous SA. Overexpressing NbLTP1 activated genes related to ROS scavenging to increase cell membrane stability and maintain redox homeostasis, confirming that an early ROS burst followed by ROS suppression at the later phases of pathogenesis is essential for resistance to TMV infection. The cell-wall localization of NbLTP1 was beneficial to viral resistance. Overall, our results showed that NbLTP1 positively regulates plant immunity against viral infection through up-regulating SA biosynthesis and its downstream signaling component, NONEXPRESSOR OF PATHOGENESIS-RELATED 1 (NPR1), which in turn activates pathogenesis-related genes, and by suppressing ROS accumulation at the later phases of viral pathogenesis.

Overexpression of LaGRAS enhances phosphorus acquisition via increased root growth of phosphorus-deficient white lupin.

The GRAS transcription factors play an indispensable role in plant growth and responses to environmental stresses. The GRAS gene family has extensively been explored in various plant species; however, the comprehensive investigation of GRAS genes in white lupin remains insufficient. In this study, bioinformatics analysis of white lupin genome revealed 51 LaGRAS genes distributed into 10 distinct phylogenetic clades. Gene structure analyses revealed that LaGRAS proteins were considerably conserved among the same subfamilies. Notably, 25 segmental duplications and a single tandem duplication showed that segmental duplication was the major driving force for the expansion of GRAS genes in white lupin. Moreover, LaGRAS genes exhibited preferential expression in young cluster root and mature cluster roots and may play key roles in nutrient acquisition, particularly phosphorus (P). To validate this, RT-qPCR analysis of white lupin plants grown under +P (normal P) and -P (P deficiency) conditions elucidated significant differences in the transcript level of GRAS genes. Among them, LaGRAS38 and LaGRAS39 were identified as potential candidates with induced expression in MCR under -P. Additionally, white lupin transgenic hairy root overexpressing OE-LaGRAS38 and OE-LaGRAS39 showed increased root growth, and P concentration in root and leaf compared to those with empty vector control, suggesting their role in P acquisition. We believe this comprehensive analysis of GRAS members in white lupin is a first step in exploring their role in the regulation of root growth, tissue development, and ultimately improving P use efficiency in legume crops under natural environments.

Twenty years of mining salt tolerance genes in soybean.

Current combined challenges of rising food demand, climate change and farmland degradation exert enormous pressure on agricultural production. Worldwide soil salinization, in particular, necessitates the development of salt-tolerant crops. Soybean, being a globally important produce, has its genetic resources increasingly examined to facilitate crop improvement based on functional genomics. In response to the multifaceted physiological challenge that salt stress imposes, soybean has evolved an array of defences against salinity. These include maintaining cell homeostasis by ion transportation, osmoregulation, and restoring oxidative balance. Other adaptations include cell wall alterations, transcriptomic reprogramming, and efficient signal transduction for detecting and responding to salt stress. Here, we reviewed functionally verified genes that underly different salt tolerance mechanisms employed by soybean in the past two decades, and discussed the strategy in selecting salt tolerance genes for crop improvement. Future studies could adopt an integrated multi-omic approach in characterizing soybean salt tolerance adaptations and put our existing knowledge into practice via omic-assisted breeding and gene editing. This review serves as a guide and inspiration for crop developers in enhancing soybean tolerance against abiotic stresses, thereby fulfilling the role of science in solving real-life problems. Supplementary Information: The online version contains supplementary material available at 10.1007/s11032-023-01383-3.

AtHDA6 functions as an H3K18ac eraser to maintain pericentromeric CHG methylation in Arabidopsis thaliana.

Pericentromeric DNA, consisting of high-copy-number tandem repeats and transposable elements, is normally silenced through DNA methylation and histone modifications to maintain chromosomal integrity and stability. Although histone deacetylase 6 (HDA6) has been known to participate in pericentromeric silencing, the mechanism is still yet unclear. Here, using whole genome bisulfite sequencing (WGBS) and chromatin immunoprecipitation-sequencing (ChIP-Seq), we mapped the genome-wide patterns of differential DNA methylation and histone H3 lysine 18 acetylation (H3K18ac) in wild-type and hda6 mutant strains. Results show pericentromeric CHG hypomethylation in hda6 mutants was mediated by DNA demethylases, not by DNA methyltransferases as previously thought. DNA demethylases can recognize H3K18ac mark and then be recruited to the chromatin. Using biochemical assays, we found that HDA6 could function as an 'eraser' enzyme for H3K18ac mark to prevent DNA demethylation. Oxford Nanopore Technology Direct RNA Sequencing (ONT DRS) also revealed that hda6 mutants with H3K18ac accumulation and CHG hypomethylation were shown to have transcriptionally active pericentromeric DNA.

Identification of the accessible chromatin regions in six tissues in the soybean.

Accessible chromatin regions (ACRs) are tightly associated with gene expressions in the genome. Conserved non-coding cis-regulatory elements, such as transcription factor binding motifs, are usually found in ACRs, indicating an essential regulatory role of ACRs in the plant genome architecture. However, there have been few studies on soybean ACRs, especially those focusing on specific tissues. Hence, in this study, with the convenient ATAC-seq, we identified the ACRs in six soybean tissues, including root, leaf bud, flower, flower bud, developing seed, and pod. In total, the ACRs occupied about 3.3% of the entire soybean genome. By integrating the results from RNA-seq and transcription factor (TF) ChIP-seq, ACRs were found to be tightly associated with gene expressions and TF binding capacities in soybean. Together, these data provide a comprehensive understanding of the genomic features of ACRs in soybean. As a collection of essential genomic resources, these processed data are made available at datahub.wildsoydb.org.

Power Up Plant Genetic Research with Genomic Data.

The official debut of the reference genome of Arabidopsis thaliana in 2000 [...].

Increased copy number of gibberellin 2-oxidase 8 genes reduced trailing growth and shoot length during soybean domestication.

Copy number variations (CNVs) play important roles in crop domestication. However, there is only very limited information on the involvement of CNVs in soybean domestication. Trailing growth and long shoots are soybean adaptations for natural habitats but cause lodging that hampers yield in cultivation. Previous studies have focused on Dt1/2 affecting the indeterminate/determinate growth habit, whereas the possible role of the gibberellin pathway remained unclear. In the present study, quantitative trait locus (QTL) mapping of a recombinant inbred population of 460 lines revealed a trailing-growth-and-shoot-length QTL. A CNV region within this QTL was identified, featuring the apical bud-expressed gibberellin 2-oxidase 8A/B, the copy numbers of which were positively correlated with expression levels and negatively with trailing growth and shoot length, and their effects were demonstrated by transgenic soybean and Arabidopsis thaliana. Based on the fixation index, this CNV region underwent intense selection during the initial domestication process.

Differential microRNA expression, microRNA arm switching, and microRNA:long noncoding RNA interaction in response to salinity stress in soybean.

BACKGROUND: Soybean is a major legume crop with high nutritional and environmental values suitable for sustainable agriculture. Noncoding RNAs (ncRNAs), including microRNAs (miRNAs) and long noncoding RNAs (lncRNAs), are important regulators of gene functions in eukaryotes. However, the interactions between these two types of ncRNAs in the context of plant physiology, especially in response to salinity stress, are poorly understood. RESULTS: Here, we challenged a cultivated soybean accession (C08) and a wild one (W05) with salt treatment and obtained their small RNA transcriptomes at six time points from both root and leaf tissues. In addition to thoroughly analyzing the differentially expressed miRNAs, we also documented the first case of miRNA arm-switching (miR166m), the swapping of dominant miRNA arm expression, in soybean in different tissues. Two arms of miR166m target different genes related to salinity stress (chloroplastic beta-amylase 1 targeted by miR166m-5p and calcium-dependent protein kinase 1 targeted by miR166m-3p), suggesting arm-switching of miR166m play roles in soybean in response to salinity stress. Furthermore, two pairs of miRNA:lncRNA interacting partners (miR166i-5p and lncRNA Gmax_MSTRG.35921.1; and miR394a-3p and lncRNA Gmax_MSTRG.18616.1) were also discovered in reaction to salinity stress. CONCLUSIONS: This study demonstrates how ncRNA involves in salinity stress responses in soybean by miRNA arm switching and miRNA:lncRNA interactions. The behaviors of ncRNAs revealed in this study will shed new light on molecular regulatory mechanisms of stress responses in plants, and hence provide potential new strategies for crop improvement.

QTL analyses of soybean root system architecture revealed genetic relationships with shoot-related traits.

KEY MESSAGE: The genetic basis of soybean root system architecture (RSA) and the genetic relationship between shoot and RSA were revealed by integrating data from recombinant inbred population grafting and QTL mapping. Variations in root system architecture (RSA) affect the functions of roots and thus play vital roles in plant adaptations and agricultural productivity. The aim of this study was to unravel the genetic relationship between RSA traits and shoot-related traits in soybean. This study characterized RSA variability at seedling stage in a recombinant inbred population, derived from a cross between cultivated soybean C08 and wild soybean W05, and performed high-resolution quantitative trait locus (QTL) mapping. In total, 34 and 41 QTLs were detected for RSA-related and shoot-related traits, respectively, constituting eight QTL clusters. Significant QTL correspondence was found between shoot biomass and RSA-related traits, consistent with significant correlations between these phenotypes. RSA-related QTLs also overlapped with selection regions in the genome, suggesting the cultivar RSA could be a partial consequence of domestication. Using reciprocal grafting, we confirmed that shoot-derived signals affected root development and the effects were controlled by multiple loci. Meanwhile, RSA-related QTLs were found to co-localize with four soybean flowering-time loci. Consistent with the phenotypes of the parental lines of our RI population, diminishing the function of flowering controlling E1 family through RNA interference (RNAi) led to reduced root growth. This implies that the flowering time-related genes within the RSA-related QTLs are actually contributing to RSA. To conclude, this study identified the QTLs that determine RSA through controlling root growth indirectly via regulating shoot functions, and discovered superior alleles from wild soybean that could be used to improve the root structure in existing soybean cultivars.

New insights into Arabidopsis transcriptome complexity revealed by direct sequencing of native RNAs.

Arabidopsis thaliana transcriptomes have been extensively studied and characterized under different conditions. However, most of the current 'RNA-sequencing' technologies produce a relatively short read length and demand a reverse-transcription step, preventing effective characterization of transcriptome complexity. Here, we performed Direct RNA Sequencing (DRS) using the latest Oxford Nanopore Technology (ONT) with exceptional read length. We demonstrate that the complexity of the A. thaliana transcriptomes has been substantially under-estimated. The ONT direct RNA sequencing identified novel transcript isoforms at both the vegetative (14-day old seedlings, stage 1.04) and reproductive stages (stage 6.00-6.10) of development. Using in-house software called TrackCluster, we determined alternative transcription initiation (ATI), alternative polyadenylation (APA), alternative splicing (AS), and fusion transcripts. More than 38 500 novel transcript isoforms were identified, including six categories of fusion-transcripts that may result from differential RNA processing mechanisms. Aided by the Tombo algorithm, we found an enrichment of m5C modifications in the mobile mRNAs, consistent with a recent finding that m5C modification in mRNAs is crucial for their long-distance movement. In summary, ONT DRS offers an advantage in the identification and functional characterization of novel RNA isoforms and RNA base modifications, significantly improving annotation of the A. thaliana genome.