The Arabidopsis Information Resource (TAIR): a comprehensive database and web-based information retrieval, analysis, and visualization system for a model plant

Involvement of MID1-COMPLEMENTING ACTIVITY 1 encoding a mechanosensitive ion channel in prehaustorium development of the stem parasitic plant Cuscuta campestris

Parasitic plants pose a substantial threat to agriculture as they attack economically important crops. The stem parasitic plant Cuscuta campestris invades the host's stem with a specialized organ referred to as the haustorium, which absorbs nutrients and water from the host. Initiation of the parasitic process in C. campestris requires mechanical stimuli to its stem. However, the mechanisms by which C. campestris perceives mechanical stimuli are largely unknown. Previous studies have shown that mechanosensitive ion channels (MSCs) are involved in the perception of mechanical stimuli. To examine if MSCs are involved in prehaustorium development upon tactile stimuli, we treated C. campestris plants with an MSC inhibitor, GsMTx-4, which resulted in a reduced density of prehaustoria. To identify the specific MSC gene involved in prehaustorium development, we analyzed the known functions and expression patterns of Arabidopsis MSC genes and selected MID1-COMPLEMENTING ACTIVITY 1 (MCA1) as a primary candidate. The MSC activity of CcMCA1 was confirmed by its ability to complement the phenotype of a yeast mid1 mutant. To evaluate the effect of CcMCA1 silencing on prehaustorium development, we performed host-induced gene silencing using Nicotiana tabacum plants that express an artificial microRNA-targeting CcMCA1. In the CcMCA1-silenced C. campestris, the number of prehaustoria per millimeter of stem length decreased, and the interval length between prehaustoria increased. Additionally, the expression levels of known genes involved in prehaustorium development, such as CcLBD25, decreased significantly in the CcMCA1-silenced plants. The results suggest that CcMCA1 is involved in prehaustorium development in C. campestris.

Identification of pine SF3B1 protein and cross-species comparison highlight its conservation and biological significance in pre-mRNA splicing regulation

As a key component of the largest subunit of the splicing machinery, SF3B1 plays essential roles in eukaryotic growth and development. However, only a few studies have focused on the evolutionary features and functions of this protein in plants. In this study, with the assistance of a bioinformatic analysis, we determined the complete coding sequence of the gene encoding the pine SF3B1 protein using RT-PCR and DNA sequencing. The evolutionary features of SF3B1 proteins were further examined based on a phylogenetic tree of SF3B1 homologous proteins from different eukaryotes, along with comprehensive comparisons of their functional domains, conserved motifs, and cis-regulatory elements and the structures of the corresponding genes. Furthermore, the effects of the splicing modulator GEX1a on several plant species were analysed, confirming that the re-identified SF3B1, with a full-length HEAT repeat domain, is expressed and functions in pre-mRNA splicing regulation in pines. In summary, we conducted a systematic cross-species comparison of SF3B1 homologous proteins, with an emphasis on complete sequence determination and the functional confirmation of pine SF3B1, illustrating the conservation of homologous proteins in plants. This study provides a valuable reference for understanding functional and regulatory mechanisms, as well as the potential applications of SF3B1.

Arabidopsis research in 2030: Translating the computable plant

Plants are essential for human survival. Over the past three decades, work with the reference plant Arabidopsis thaliana has significantly advanced plant biology research. One key event was the sequencing of its genome 25 years ago, which fostered many subsequent research technologies and datasets. Arabidopsis has been instrumental in elucidating plant-specific aspects of biology, developing research tools, and translating findings to crop improvement. It not only serves as a model for understanding plant biology and but also biology in other fields, with discoveries in Arabidopsis also having led to applications in human health, including insights into immunity, protein degradation, and circadian rhythms. Arabidopsis research has also fostered the development of tools useful for the wider biological research community, such as optogenetic systems and auxin-based degrons. This 4th Multinational Arabidopsis Steering Committee Roadmap outlines future directions, with emphasis on computational approaches, research support, translation to crops, conference accessibility, coordinated research efforts, climate change mitigation, sustainable production, and fundamental research. Arabidopsis will remain a nexus for discovery, innovation, and application, driving advances in both plant and human biology to the year 2030, and beyond.

Establishing a comprehensive web-based analysis platform for Nicotiana benthamiana genome and transcriptome

Nicotiana benthamiana has long served as a crucial plant material extensively used in plant physiology research, particularly in the field of plant pathology, because of its high susceptibility to plant viruses. Additionally, it serves as a production platform to test vaccines and other valuable substances. Among its approximately 3.1 Gb genome, 57 583 genes have been annotated within a 61 Mb region. We created a comprehensive and easy-to-use platform to use transcriptomes for modern annotation. These tools allow to visualize gene expression profiles, draw molecular evolutionary phylogenetic trees of gene families, perform functional enrichment analyses, and facilitate output downloads. To demonstrate their utility, we analyzed the gene expression profiles of enzymes within the nicotine biosynthesis pathway, a secondary metabolic pathway characteristic of the Nicotiana genus. Using the developed tool, expression profiles of the nicotine biosynthesis pathway genes were generated. The expression patterns of eight gene groups in the pathway were strongly expressed in the roots and weakly expressed in leaves and flowers of N. benthamiana. The results were consistent with the established gene expression profiles in Nicotiana tabacum and provided insights into gene family composition and expression trends. The compilation of this database tool can facilitate genetic analysis of N. benthamiana in the future.

The genetically programmed rhythmic alteration of diurnal gene expression in the aged Arabidopsis leaves

The circadian clock regulates the daily pattern of temporal gene expression. In Arabidopsis, aging is associated with a shortening of the endogenous period of circadian rhythms under circadian conditions. However, the functional link between the circadian clock and aging under diurnal conditions and its physiological relevance remain elusive. In this study, we investigate and characterize the effect of aging on the waveforms of rhythmic gene expression patterns under light/dark cycles. Our analysis revealed that the diurnal rhythmic patterns of core clock genes undergo significant rhythmic alteration with phase shift and change of waveforms in aged plants compared to younger plants. Transcriptomic analysis indicated that this age-dependent rhythmic alteration occurs not only in core clock genes but also globally. Due to the rhythmic alteration patterns of the diurnal rhythmic gene expression, aged plants experience subjectively a shorter day and longer night. We also observed that genetic mutants of core clock component genes exhibited broadly yet distinctively altered changes in diurnal rhythmic gene expression patterns as aging progresses. Collectively, our findings support that age-dependent rhythmic alteration of diurnal gene expression rhythms reprograms the timetable of daily gene expression, leading to the physiological changes required for plant senescence.

Comprehensive analysis of AHL genes in Malus domestica reveals the critical role of MdAHL6 in flowering induction

AT-hook motif nuclear localized (AHL) genes are crucial in various biological processes, yet the AHL gene family in apples has remained largely unexplored. In this study, we isolated 36 MdAHL genes from the apple genome and grouped them into two distinct clades. We characterized the gene structure, conserved motifs, protein biochemical properties, and promoter regions of the MdAHL genes. Transcriptional analysis revealed that MdAHL genes are preferentially and predominantly expressed in flowers and leaves. Notably, during the floral induction phase, the MdAHL6 gene exhibited remarkably high transcriptional activity. Overexpression of MdAHL6 resulted in shortened hypocotyls and delayed flowering by regulating hypocotyl- and floral-related genes. Y1H, EMSA, GUS activity, and molecular docking assays revealed that MdAHL6 directly binds to AT-rich regions, inhibiting the expression of FLOWERING LOCUS T (MdFT). Furthermore, Y2H, pull-down, and BiFC assays demonstrated a physical interaction between MdAHL6 and the class II knotted-like transcription factor MdKNOX19, which significantly enhances the inhibitory effect of MdAHL6 on MdFT expression. This comprehensive initial analysis unveils the critical role of the MdKNOX19-MdAHL6-MdFT module in flowering induction and lays a theoretical foundation for future functional exploration.

Genome-wide identification of the Dof gene family: How it plays a part in mediating cold stress response in Prunus mume

DNA binding with a finger transcription factor (Dof) takes part in several plant physiological activities such as seed germination, flowering time, cold and drought resistance. Although the function, molecular phylogeny and expression pattern of Dof genes in Prunus mume was not clear yet. Here, the gene structure, motif, chromosome location and phylogenetic relationship of the Dof gene family in Prunus species was explored. We identified 24 members of the Dof gene family from P. mume, which were divided into 3 different subgroups. All these PmDof genes can be mapped to the pseudochromosome. Only one pair of tandem duplication genes are located in Chr3, whereas 8 pairs of segmentally duplicated PmDof genes located in Chr1, Chr2, Chr4, Chr5, and Chr7. Motif and gene structure analysis showed that each group had a similar conservative motif and similar exon/intron composition. Cis-acting elements analysis indicate that PmDofs may be involved in regulating abiotic stress response. Gene expression patterns showed that most PmDofs genes were specifically expressed in different tissues and at different stages. We next found that PmDofs genes display an obvious expression preference or specificity in cold stress response according to qRT-PCR analysis. We further observe a great cold resistance in PmDof10/11/20 OE lines, they showed lower electrolyte leakage rate, MDA content and higher soluble sugar/protein, POD/SOD/proline content than WT after -5 °C 6h freezing treatment. This research offers fresh perspectives on the development of PmDofs, enhancing our comprehension of the structure and role of plant Dof gene families.

Integrative Analysis of Transcriptome and Metabolome Reveals the Pivotal Role of the NAM Family Genes in Oncidium hybridum Lodd. Pseudobulb Growth

Oncidium hybridum Lodd. is an important ornamental flower that is used as both a cut flower and a potted plant around the world; additionally, its pseudobulbs serve as essential carriers for floral organs and flower development. The NAM gene family is crucial for managing responses to various stresses as well as regulating growth in plants. However, the mechanisms by which NAM genes regulate the development of pseudobulbs remain unclear. In this study, a total of 144 NAM genes harboring complete structural domains were identified in O. hybridum. The 144 NAM genes were systematically classified into 14 distinct subfamilies via phylogenetic analysis. Delving deeper into the conserved motifs revealed that motifs 1-6 exhibited remarkable conservation, while motifs 7-10 presented in a few NAM genes only. Notably, NAM genes sharing identical specific motifs were classified into the same subfamily, indicating functional relatedness. Furthermore, the examination of occurrences of gene duplication indicated that the NAM genes display 16 pairs of tandem duplications along with five pairs of segmental duplications, suggesting their role in genetic diversity and potential adaptive evolution. By conducting a correlation analysis integrating transcriptomics and metabolomics at four stages of pseudobulb development, we found that OhNAM023, OhNAM030, OhNAM007, OhNAM019, OhNAM083, OhNAM047, OhNAM089, and OhNAM025 exhibited significant relationships with the endogenous plant hormones jasmonates (JAs), hinting at their potential involvement in hormonal signaling. Additionally, OhNAM089, OhNAM025, OhNAM119, OhNAM055, and OhNAM136 showed strong links with abscisic acid (ABA) and abscisic acid glucose ester (ABA-GE), suggesting the possible regulatory function of these NAM genes in plant growth and stress responses. The 144 NAM genes identified in this study provide a basis for subsequent research and contribute to elucidating the intricate molecular mechanisms of NAM genes in Oncidium and potentially in other species.

Genome-wide identification, phylogeny and expression analysis of Hsf gene family in Verbena bonariensis under low-temperature stress

BACKGROUND

The heat shock transcription factor (Hsf) is a crucial regulator of plant stress resistance, playing a key role in plant stress response, growth, and development regulation.

RESULTS

In this study, we utilized bioinformatics tools to screen 25 VbHsf members, which were named VbHsf1-VbHsf25. We used bioinformatics methods to analyze the sequence structure, physicochemical properties, conserved motifs, phylogenetic evolution, chromosome localization, promoter cis-acting elements, collinearity, and gene expression of Hsf heat shock transcription factor family members under low-temperature stress. The results revealed that the majority of the Hsf genes contained motif1, motif2, and motif3, signifying that these three motifs were highly conserved in the Hsf protein sequence of Verbena bonariensis. Although there were some variations in motif deletion among the members, the domain remained highly conserved. The theoretical isoelectric point ranged from 4.17 to 9.71, with 21 members being unstable proteins and the remainder being stable proteins. Subcellular localization predictions indicated that all members were located in the nucleus. Phylogenetic analysis of the Hsf gene family in V. bonariensis and Arabidopsis thaliana revealed that the Hsf gene family of V. bonariensis could be categorized into three groups, with group A comprising 17 members and group C having at least two members. Among the 25 Hsf members, there were 1-3 exons located on seven chromosome fragments, which were unevenly distributed. Collinearity analysis demonstrated the presence of seven pairs of homologous genes in the VbHsf gene family. The Ka/Ks ratios were less than one, indicating that the VbHsf gene underwent purification selection pressure. Additionally, nine genes in V. bonariensis were found to have collinearity with A. thaliana. Promoter analysis revealed that the promoters of all VbHsf genes contained various types of cis-acting elements related to hormones and stress. Based on RNA-seq data, qRT-PCR analysis of six highly expressed genes was performed, and it was found that VbHsf5, VbHsf14, VbHsf17, VbHsf18, VbHsf20 and VbHsf21 genes were highly expressed at 12 h of low-temperature treatment, and the expression decreased after 24 h, among which VbHsf14 was up-regulated at 12 h of low-temperature by 70-fold.

CONCLUSIONS

Our study may help reveal the important roles of Hsf in plant development and show insight for the further molecular breeding of V. bonariensis.

Root Primordium Defective 1 Encodes an Essential PORR Protein Required for the Splicing of Mitochondria-Encoded Group II Introns and for Respiratory Complex I Biogenesis

Cellular respiration involves complex organellar metabolic activities that are pivotal for plant growth and development. Mitochondria contain their own genetic system (mitogenome, mtDNA), which encodes key elements of the respiratory machinery. Plant mtDNAs are notably larger than their counterparts in Animalia, with complex genome organization and gene expression characteristics. The maturation of the plant mitochondrial transcripts involves extensive RNA editing, trimming and splicing events. These essential processing steps rely on the activities of numerous nuclear-encoded cofactors, which may also play key regulatory roles in mitochondrial biogenesis and function and hence in plant physiology. Proteins that harbor the plant organelle RNA recognition (PORR) domain are represented in a small gene family in plants. Several PORR members, including WTF1, WTF9 and LEFKOTHEA, are known to act in the splicing of organellar group II introns in angiosperms. The AT4G33495 gene locus encodes an essential PORR protein in Arabidopsis, termed ROOT PRIMORDIUM DEFECTIVE 1 (RPD1). A null mutation of At.RPD1 causes arrest in early embryogenesis, while the missense mutant lines, rpd1.1 and rpd1.2, exhibit a strong impairment in root development and retarded growth phenotypes, especially under high-temperature conditions. Here, we further show that RPD1 functions in the splicing of introns that reside in the coding regions of various complex I (CI) subunits (i.e. nad2, nad4, nad5 and nad7), as well as in the maturation of the ribosomal rps3 pre-RNA in Arabidopsis mitochondria. The altered growth and developmental phenotypes and modified respiration activities are tightly correlated with respiratory chain CI defects in rpd1 mutants.

The Arabidopsis Information Resource in 2024

Since 1999, The Arabidopsis Information Resource (www.arabidopsis.org) has been curating data about the Arabidopsis thaliana genome. Its primary focus is integrating experimental gene function information from the peer-reviewed literature and codifying it as controlled vocabulary annotations. Our goal is to produce a "gold standard" functional annotation set that reflects the current state of knowledge about the Arabidopsis genome. At the same time, the resource serves as a nexus for community-based collaborations aimed at improving data quality, access, and reuse. For the past decade, our work has been made possible by subscriptions from our global user base. This update covers our ongoing biocuration work, some of our modernization efforts that contribute to the first major infrastructure overhaul since 2011, the introduction of JBrowse2, and the resource's role in community activities such as organizing the structural reannotation of the genome. For gene function assessment, we used gene ontology annotations as a metric to evaluate: (1) what is currently known about Arabidopsis gene function and (2) the set of "unknown" genes. Currently, 74% of the proteome has been annotated to at least one gene ontology term. Of those loci, half have experimental support for at least one of the following aspects: molecular function, biological process, or cellular component. Our work sheds light on the genes for which we have not yet identified any published experimental data and have no functional annotation. Drawing attention to these unknown genes highlights knowledge gaps and potential sources of novel discoveries.

Spatially resolved proteomics of the Arabidopsis stomatal lineage identifies polarity complexes for cell divisions and stomatal pores

Cell polarity is used to guide asymmetric divisions and create morphologically diverse cells. We find that two oppositely oriented cortical polarity domains present during the asymmetric divisions in the Arabidopsis stomatal lineage are reconfigured into polar domains marking ventral (pore-forming) and outward-facing domains of maturing stomatal guard cells. Proteins that define these opposing polarity domains were used as baits in miniTurboID-based proximity labeling. Among differentially enriched proteins, we find kinases, putative microtubule-interacting proteins, and polar SOSEKIs with their effector ANGUSTIFOLIA. Using AI-facilitated protein structure prediction models, we identify potential protein-protein interaction interfaces among them. Functional and localization analyses of the polarity protein OPL2 and its putative interaction partners suggest a positive interaction with mitotic microtubules and a role in cytokinesis. This combination of proteomics and structural modeling with live-cell imaging provides insights into how polarity is rewired in different cell types and cell-cycle stages.

Transcription and splicing variations of SR genes accompany with genome-wide accumulation of long-introns in pine

Most of mRNAs in Eukaryote were matured after the removal of introns in their pre-mRNA transcripts. Serine/arginine-rich (SR) proteins are a group of splicing regulators regulating the splicing processes globally. Expressions of SR proteins themselves were extensively regulated, at both transcription and splicing levels, under different environmental conditions, specially heat stress conditions. The pine genome is characterized by super-long and easily methylated introns in a large number of genes that derived from the extensive accumulation of transposons (TEs). Here, we identified and analyzed the phylogenetic characteristics of 24 SR proteins and their encoding genes from the pine genome. Then we explored transcription and pre-mRNA splicing expression patterns of SR genes in P. massoniana seedlings under normal and heat stress temperature conditions. Our results showed that the transcription patterns of SR genes in pine exhibited significant changes compared to other plant species, and these changes were not strictly correlated with the intron length and DNA methylation intensity of the SR genes. Interestingly, none of the long introns of SR genes underwent alternative splicing (AS) in our experiment. Furthermore, the intensity of AS regulation may be related to the potential DNA methylation intensity of SR genes. Taken together, this study explores for the first time the characteristics of significant variations in the transcription and splicing patterns of SR proteins in a plant species with an over-accumulation of super-long introns.

Phosphoregulation in the N-terminus of NRT2.1 affects nitrate uptake by controlling the interaction of NRT2.1 with NAR2.1 and kinase HPCAL1 in Arabidopsis

NRT2.1, the major high affinity nitrate transporter in roots, can be phosphorylated at five different sites within the N- and the C-terminus. Here, we characterized the functional relationship of two N-terminal phosphorylation sites, S21 and S28, in Arabidopsis. Based on a site-specific correlation network, we identified a receptor kinase (HPCAL1, AT5G49770), phosphorylating NRT2.1 at S21 and resulting in active nitrate uptake. HPCAL1 itself was regulated by phosphorylation at S839 and S870 within its kinase domain. In the active state, when S839 was dephosphorylated and S870 was phosphorylated, HPCAL1 was found to interact with the N-terminus of NRT2.1, mainly when S28 was dephosphorylated. Phosphorylation of NRT2.1 at S21 resulted in a reduced interaction of NRT2.1 with its activator NAR2.1, but nitrate transport activity remained. By contrast, phosphorylated NRT2.1 at S28 enhanced the interaction with NAR2.1, but reduced the interaction with HPCAL1. Here we identified HPCAL1 as the kinase affecting this phospho-switch through phosphorylation of NRT2.1 at S21.

Arabidopsis as a model for translational research

Arabidopsis thaliana is currently the most-studied plant species on earth, with an unprecedented number of genetic, genomic, and molecular resources having been generated in this plant model. In the era of translating foundational discoveries to crops and beyond, we aimed to highlight the utility and challenges of using Arabidopsis as a reference for applied plant biology research, agricultural innovation, biotechnology, and medicine. We hope that this review will inspire the next generation of plant biologists to continue leveraging Arabidopsis as a robust and convenient experimental system to address fundamental and applied questions in biology. We aim to encourage lab and field scientists alike to take advantage of the vast Arabidopsis datasets, annotations, germplasm, constructs, methods, molecular and computational tools in our pursuit to advance understanding of plant biology and help feed the world's growing population. We envision that the power of Arabidopsis-inspired biotechnologies and foundational discoveries will continue to fuel the development of resilient, high-yielding, nutritious plants for the betterment of plant and animal health and greater environmental sustainability.

Highly differentiated genomic properties underpin the different cell walls of Poaceae and eudicots

Plant cell walls of Poaceae and eudicots differ substantially, both in the content and composition of their components. However, the genomic and genetic basis underlying these differences is not fully resolved. In this research, we analyzed multiple genomic properties of 150 cell wall gene families across 169 angiosperm genomes. The properties analyzed include gene presence/absence, copy number, synteny, occurrence of tandem gene clusters, and phylogenetic gene diversity. Results revealed a profound genomic differentiation of cell wall genes between Poaceae and eudicots, often associated with the cell wall diversity between these plant groups. For example, overall patterns of gene copy number variation and synteny were clearly divergent between Poaceae and eudicot species. Moreover, differential Poaceae-eudicot copy number and genomic contexts were observed for all the genes within the BEL1-like HOMEODOMAIN 6 regulatory pathway, which respectively induces and represses secondary cell wall synthesis in Poaceae and eudicots. Similarly, divergent synteny, copy number, and phylogenetic gene diversification were observed for the major biosynthetic genes of xyloglucans, mannans, and xylans, potentially contributing to the differences in content and types of hemicellulosic polysaccharides differences in Poaceae and eudicot cell walls. Additionally, the Poaceae-specific tandem clusters and/or higher copy number of PHENYLALANINE AMMONIA-LYASE, CAFFEIC ACID O-METHYLTRANSFERASE, or PEROXIDASE genes may underly the higher content and larger variety of phenylpropanoid compounds observed in Poaceae cell walls. All these patterns are discussed in detail in this study, along with their evolutionary and biological relevance for cell wall (genomic) diversification between Poaceae and eudicots.

Phytocystatin 6 is a context-dependent, tight-binding inhibitor of Arabidopsis thaliana legumain isoform β

Plant legumains are crucial for processing seed storage proteins and are critical regulators of plant programmed cell death. Although research on legumains boosted recently, little is known about their activity regulation. In our study, we used pull-down experiments to identify AtCYT6 as a natural inhibitor of legumain isoform β (AtLEGβ) in Arabidopsis thaliana. Biochemical analysis revealed that AtCYT6 inhibits both AtLEGβ and papain-like cysteine proteases through two separate cystatin domains. The N-terminal domain inhibits papain-like proteases, while the C-terminal domain inhibits AtLEGβ. Furthermore, we showed that AtCYT6 interacts with legumain in a substrate-like manner, facilitated by a conserved asparagine residue in its reactive center loop. Complex formation was additionally stabilized by charged exosite interactions, contributing to pH-dependent inhibition. Processing of AtCYT6 by AtLEGβ suggests a context-specific regulatory mechanism with implications for plant physiology, development, and programmed cell death. These findings enhance our understanding of AtLEGβ regulation and its broader physiological significance.

SHI family transcription factors regulate an interspecific barrier

Pre-zygotic interspecies incompatibility in angiosperms is an important mechanism to prevent unfavourable hybrids between species. Here we report our identification of STIGMATIC PRIVACY 2 (SPRI2), a transcription factor that has a zinc-finger domain and regulates interspecies barriers in Arabidopsis thaliana, via genome-wide association study. Knockout analysis of SPRI2/SRS7 and its paralogue SPRI2-like/SRS5 demonstrated their necessity in rejecting male pollen from other species within female pistils. Additionally, they govern mRNA transcription of xylan O-acetyltransferases (TBL45 and TBL40) related to cell wall modification, alongside SPRI1, a pivotal transmembrane protein for interspecific pollen rejection. SPRI2/SRS7 is localized as condensed structures in the nucleus formed via liquid-liquid phase separation (LLPS), and a prion-like sequence in its amino-terminal region was found to be responsible for the formation of the condensates. The LLPS-regulated SPRI2/SRS7 discovered in this study may contribute to the establishment of interspecific reproductive barriers through the transcriptional regulation of cell wall modification genes and SPRI1.

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.

Hidden genetic variation in plasticity provides the potential for rapid adaptation to novel environments

Rapid environmental change is forcing populations into environments where plasticity will no longer maintain fitness. When populations are exposed to novel environments, evolutionary theory predicts that genetic variation in fitness will increase and should be associated with genetic differences in plasticity. If true, then genetic variation in plasticity can increase adaptive potential in novel environments, and population persistence via evolutionary rescue is more likely. To test whether genetic variation in fitness increases in novel environments and is associated with plasticity, we transplanted 8149 clones of 314 genotypes of a Sicilian daisy (Senecio chrysanthemifolius) within and outside its native range, and quantified genetic variation in fitness, and plasticity in leaf traits and gene expression. Although mean fitness declined by 87% in the novel environment, genetic variance in fitness increased threefold and was correlated with plasticity in leaf traits. High fitness genotypes showed greater plasticity in gene expression, but lower plasticity in most leaf traits. Interestingly, genotypes with the highest fitness in the novel environment had the lowest fitness at the native site. These results suggest that standing genetic variation in plasticity could help populations to persist and adapt to novel environments, despite remaining hidden in native environments.

Integrating multiple regulations on enzyme activity: the case of phosphoenolpyruvate carboxykinases

Data on protein post-translational modifications (PTMs) increased exponentially in the last years due to the refinement of mass spectrometry techniques and the development of databases to store and share datasets. Nevertheless, these data per se do not create comprehensive biochemical knowledge. Complementary studies on protein biochemistry are necessary to fully understand the function of these PTMs at the molecular level and beyond, for example, designing rational metabolic engineering strategies to improve crops. Phosphoenolpyruvate carboxykinases (PEPCKs) are critical enzymes for plant metabolism with diverse roles in plant development and growth. Multiple lines of evidence showed the complex regulation of PEPCKs, including PTMs. Herein, we present PEPCKs as an example of the integration of combined mechanisms modulating enzyme activity and metabolic pathways. PEPCK studies strongly advanced after the production of the recombinant enzyme and the establishment of standardized biochemical assays. Finally, we discuss emerging open questions for future research and the challenges in integrating all available data into functional biochemical models.

A phylotranscriptomic dataset of angiosperm species under cold stress

Angiosperms are one of the most diverse and abundant plant groups that are widely distributed on Earth, from tropical to temperate and polar zones. The wide distribution of angiosperms may be attributed to the evolution of sophisticated mechanisms of environmental adaptability, including cold tolerance. Since the development of high-throughput sequencing, transcriptome has been widely utilized to gain insights into the molecular mechanisms of plants in response to cold stress. However, previous studies generally focused on single or two species, and comparative transcriptome analyses for multispecies responding to cold stress were limited. In this study, we selected 11 representative angiosperm species, performed phylotranscriptome experiments at four time points before and after cold stress, and presented a profile of cold-induced transcriptome changes in angiosperms. Our multispecies cold-responsive RNA-seq datasets provide valuable references for exploring conserved and evolutionary mechanisms of angiosperms in adaptation to cold stress.

Genome-wide analysis revealed the stepwise origin and functional diversification of HSDs from lower to higher plant species

Hydroxysteroid dehydrogenase (HSDs) is an oil-body sterol protein (steroleosin) with an NADP(H) binding domain that belongs to the short-chain dehydrogenase/reductase (SDR) superfamily. There are numerous studies on the characterization of HSDs in plants. However, thus far, the evolutionary differentiation and divergence analysis of these genes remain to be explored. The current study used an integrated method to elucidate the sequential evolution of HSDs in 64 sequenced plant genomes. Analyses were conducted on their origins, distribution, duplication, evolutionary paths, domain functions, motif composition, properties, and cis-elements. Results indicate that except for algae, HSD1 was widely distributed in plant species ranging from lower to higher plants, while HSD5 was restricted to terrestrial plants, and HSD2 was identified in fewer monocots and several dicot plants. Phylogenetic analysis of HSD proteins revealed that monocotyledonous HSD1 in moss and ferns appeared closest to the outgroup, V. carteri HSD-like, M. musculus HSD1, and H. sapiens HSD1. These data support the hypothesis that HSD1 originated in bryophytes and then in non-vascular and vascular plants, followed by HSD5 only in land plants. Gene structure analysis suggests that HSDs in plant species came up with a fixed number of six exons, and the intron phase was primarily 0, 1, 0, 0, and 0. Similarly, duplication analysis revealed that segmental duplications were the main reason for HSDs in plant species. Physicochemical properties suggest that dicotyledonous HSD1s and HSD5s were mainly acidic. The monocotyledonous HSD1s and HSD2s and the dicotyledonous HSD2s, HSD3s, HSD4s, and HSD6s were mainly basic, implying that HSDs in plants may have a variety of functions. Cis-regulatory elements and expression analysis revealed that HSDs in plants might have roles in several abiotic stresses. Due to the high expression of HSD1s and HSD5s in seeds, these HSDs in plants may have roles in fatty acid accumulation and degradation.

Identification of new potential downstream transcriptional targets of the strigolactone pathway including glucosinolate biosynthesis

Strigolactones regulate shoot branching and many aspects of plant growth, development, and allelopathy. Strigolactones are often discussed alongside auxin because they work together to inhibit shoot branching. However, the roles and mechanisms of strigolactones and how they act independently of auxin are still elusive. Additionally, there is still much in general to be discovered about the network of molecular regulators and their interactions in response to strigolactones. Here, we conducted an experiment in Arabidopsis with physiological treatments and strigolactone mutants to determine transcriptional pathways associated with strigolactones. The three physiological treatments included shoot tip removal with and without auxin treatment and treatment of intact plants with the auxin transport inhibitor, N-1-naphthylphthalamic acid (NPA). We identified the glucosinolate biosynthesis pathway as being upregulated across strigolactone mutants indicating strigolactone-glucosinolate crosstalk. Additionally, strigolactone application cannot restore the highly branched phenotype observed in glucosinolate biosynthesis mutants, placing glucosinolate biosynthesis downstream of strigolactone biosynthesis. Oxidative stress genes were enriched across the experiment suggesting that this process is mediated through multiple hormones. Here, we also provide evidence supporting non-auxin-mediated, negative feedback on strigolactone biosynthesis. Increases in strigolactone biosynthesis gene expression seen in strigolactone mutants could not be fully restored by auxin. By contrast, auxin could fully restore auxin-responsive gene expression increases, but not sugar signaling-related gene expression. Our data also point to alternative roles of the strigolactone biosynthesis genes and potential new signaling functions of strigolactone precursors. In this study, we identify a strigolactone-specific regulation of glucosinolate biosynthesis genes indicating that the two are linked and may work together in regulating stress and shoot ranching responses in Arabidopsis. Additionally, we provide evidence for non-auxinmediated feedback on strigolactone biosynthesis and discuss this in the context of sugar signaling.

Evaluation of N 6-methyldeoxyadenosine antibody-based genomic profiling in eukaryotes

Low-level DNA N 6-methyldeoxyadenosine (DNA-m6A) has recently been reported across various eukaryotes. Although anti-m6A antibody-based approaches are commonly used to measure DNA-m6A levels, this approach is known to be confounded by DNA secondary structures, RNA contamination, and bacterial contamination. To evaluate for these confounding features, we introduce an approach for systematically validating the selectivity of antibody-based DNA-m6A methods and use a highly selective anti-DNA-m6A antibody to reexamine patterns of DNA-m6A in C. reinhardtii, A. thaliana, and D. melanogaster Our findings raise caution about the use of antibody-based methods for endogenous m6A quantification and mapping in eukaryotes.

Genes encoding cytochrome P450 monooxygenases and glutathione S-transferases associated with herbicide resistance evolved before the origin of land plants

Cytochrome P450 (CYP) monooxygenases and glutathione S-transferases (GST) are enzymes that catalyse chemical modifications of a range of organic compounds. Herbicide resistance has been associated with higher levels of CYP and GST gene expression in some herbicide-resistant weed populations compared to sensitive populations of the same species. By comparing the protein sequences of 9 representative species of the Archaeplastida-the lineage which includes red algae, glaucophyte algae, chlorophyte algae, and streptophytes-and generating phylogenetic trees, we identified the CYP and GST proteins that existed in the common ancestor of the Archaeplastida. All CYP clans and all but one land plant GST classes present in land plants evolved before the divergence of streptophyte algae and land plants from their last common ancestor. We also demonstrate that there are more genes encoding CYP and GST proteins in land plants than in algae. The larger numbers of genes among land plants largely results from gene duplications in CYP clans 71, 72, and 85 and in the GST phi and tau classes [1,2]. Enzymes that either metabolise herbicides or confer herbicide resistance belong to CYP clans 71 and 72 and the GST phi and tau classes. Most CYP proteins that have been shown to confer herbicide resistance are members of the CYP81 family from clan 71. These results demonstrate that the clan and class diversity in extant plant CYP and GST proteins had evolved before the divergence of land plants and streptophyte algae from a last common ancestor estimated to be between 515 and 474 million years ago. Then, early in embryophyte evolution during the Palaeozoic, gene duplication in four of the twelve CYP clans, and in two of the fourteen GST classes, led to the large numbers of CYP and GST proteins found in extant land plants. It is among the genes of CYP clans 71 and 72 and GST classes phi and tau that alleles conferring herbicide resistance evolved in the last fifty years.

Identification, characterization of Apyrase (APY) gene family in rice (Oryza sativa) and analysis of the expression pattern under various stress conditions

Apyrase (APY) is a nucleoside triphosphate (NTP) diphosphohydrolase (NTPDase) which is a member of the superfamily of guanosine diphosphatase 1 (GDA1)-cluster of differentiation 39 (CD39) nucleoside phosphatase. Under various circumstances like stress, cell growth, the extracellular adenosine triphosphate (eATP) level increases, causing a detrimental influence on cells such as cell growth retardation, ROS production, NO burst, and apoptosis. Apyrase hydrolyses eATP accumulated in the extracellular membrane during stress, wounds, into adenosine diphosphate (ADP) and adenosine monophosphate (AMP) and regulates the stress-responsive pathway in plants. This study was designed for the identification, characterization, and for analysis of APY gene expression in Oryza sativa. This investigation discovered nine APYs in rice, including both endo- and ecto-apyrase. According to duplication event analysis, in the evolution of OsAPYs, a significant role is performed by segmental duplication. Their role in stress control, hormonal responsiveness, and the development of cells is supported by the corresponding cis-elements present in their promoter regions. According to expression profiling by RNA-seq data, the genes were expressed in various tissues. Upon exposure to a variety of biotic as well as abiotic stimuli, including anoxia, drought, submergence, alkali, heat, dehydration, salt, and cold, they showed a differential expression pattern. The expression analysis from the RT-qPCR data also showed expression under various abiotic stress conditions, comprising cold, salinity, cadmium, drought, submergence, and especially heat stress. This finding will pave the way for future in-vivo analysis, unveil the molecular mechanisms of APY genes in stress response, and contribute to the development of stress-tolerant rice varieties.

Silencing of a mannitol transport gene in Phelipanche aegyptiaca by the tobacco rattle virus system reduces the parasite germination on the host root

Root parasitic weed Phelipanche aegyptiaca is an obligate plant parasite that causes severe damage to host crops. Agriculture crops mainly belong to the Brassicaceae, Leguminosae, Cruciferae, and Solanaceae plant families affected by this parasitic weed, leading to the devastating loss of crop yield and economic growth. This root-specific parasitic plant is not able to complete its life cycle without a suitable host and is dependent on the host plant for nutrient uptake and germination. Therefore, selected parasitic genes of P. aegyptiaca which were known to be upregulated upon interaction with the host were chosen. These genes are essential for parasitism, and reduced activity of these genes could affect host-parasitic interaction and provide resistance to the host against these parasitic weeds. To check and examine the role of these parasitic genes which can affect the development of host resistance, we silenced selected genes in the P. aegyptiaca using the tobacco rattle virus (TRV) based virus-induced gene silencing (VIGS) method. Our results demonstrated that the total number of P. aegyptiaca parasite tubercles attached to the root of the host plant Nicotiana benthamiana was substantially decreased in all the silenced plants. However, silencing of the P. aegyptiaca MNT1 gene which encodes the mannitol transporter showed a significantly reduced number of germinated shoots and tubercles. Thus, our study indicates that the mannitol transport gene of P. aegyptiaca plays a crucial role in parasitic germination, and silencing of the PaMNT1 gene abolishes the germination of parasites on the host roots.

Genome-wide identification, comprehensive characterization of transcription factors, cis-regulatory elements, protein homology, and protein interaction network of DREB gene family in Solanum lycopersicum

Tomato is a drought-sensitive crop which has high susceptibility to adverse climatic changes. Dehydration-responsive element-binding (DREB) are significant plant transcription factors that have a vital role in regulating plant abiotic stress tolerance by networking with DRE/CRT cis-regulatory elements in response to stresses. In this study, bioinformatics analysis was performed to conduct the genome-wide identification and characterization of DREB genes and promoter elements in Solanum lycopersicum. In genome-wide coverage, 58 SlDREB genes were discovered on 12 chromosomes that justified the criteria of the presence of AP2 domain as conserved motifs. Intron-exon organization and motif analysis showed consistency with phylogenetic analysis and confirmed the absence of the A3 class, thus dividing the SlDREB genes into five categories. Gene expansion was observed through tandem duplication and segmental duplication gene events in SlDREB genes. Ka/Ks values were calculated in ortholog pairs that indicated divergence time and occurrence of purification selection during the evolutionary period. Synteny analysis demonstrated that 32 out of 58 and 47 out of 58 SlDREB genes were orthologs to Arabidopsis and Solanum tuberosum, respectively. Subcellular localization predicted that SlDREB genes were present in the nucleus and performed primary functions in DNA binding to regulate the transcriptional processes according to gene ontology. Cis-acting regulatory element analysis revealed the presence of 103 motifs in 2.5-kbp upstream promoter sequences of 58 SlDREB genes. Five representative SlDREB proteins were selected from the resultant DREB subgroups for 3D protein modeling through the Phyre2 server. All models confirmed about 90% residues in the favorable region through Ramachandran plot analysis. Moreover, active catalytic sites and occurrence in disorder regions indicated the structural and functional flexibility of SlDREB proteins. Protein association networks through STRING software suggested the potential interactors that belong to different gene families and are involved in regulating similar functional and biological processes. Transcriptome data analysis has revealed that the SlDREB gene family is engaged in defense response against drought and heat stress conditions in tomato. Overall, this comprehensive research reveals the identification and characterization of SlDREB genes that provide potential knowledge for improving abiotic stress tolerance in tomato.

Emergence of Novel RNA-Editing Sites by Changes in the Binding Affinity of a Conserved PPR Protein

RNA editing converts cytidines to uridines in plant organellar transcripts. Editing typically restores codons for conserved amino acids. During evolution, specific C-to-U editing sites can be lost from some plant lineages by genomic C-to-T mutations. By contrast, the emergence of novel editing sites is less well documented. Editing sites are recognized by pentatricopeptide repeat (PPR) proteins with high specificity. RNA recognition by PPR proteins is partially predictable, but prediction is often inadequate for PPRs involved in RNA editing. Here we have characterized evolution and recognition of a recently gained editing site. We demonstrate that changes in the RNA recognition motifs that are not explainable with the current PPR code allow an ancient PPR protein, QED1, to uniquely target the ndhB-291 site in Brassicaceae. When expressed in tobacco, the Arabidopsis QED1 edits 33 high-confident off-target sites in chloroplasts and mitochondria causing a spectrum of mutant phenotypes. By manipulating the relative expression levels of QED1 and ndhB-291, we show that the target specificity of the PPR protein depends on the RNA:protein ratio. Finally, our data suggest that the low expression levels of PPR proteins are necessary to ensure the specificity of editing site selection and prevent deleterious off-target editing.

Multi-Omics Approaches and Resources for Systems-Level Gene Function Prediction in the Plant Kingdom

In higher plants, the complexity of a system and the components within and among species are rapidly dissected by omics technologies. Multi-omics datasets are integrated to infer and enable a comprehensive understanding of the life processes of organisms of interest. Further, growing open-source datasets coupled with the emergence of high-performance computing and development of computational tools for biological sciences have assisted in silico functional prediction of unknown genes, proteins and metabolites, otherwise known as uncharacterized. The systems biology approach includes data collection and filtration, system modelling, experimentation and the establishment of new hypotheses for experimental validation. Informatics technologies add meaningful sense to the output generated by complex bioinformatics algorithms, which are now freely available in a user-friendly graphical user interface. These resources accentuate gene function prediction at a relatively minimal cost and effort. Herein, we present a comprehensive view of relevant approaches available for system-level gene function prediction in the plant kingdom. Together, the most recent applications and sought-after principles for gene mining are discussed to benefit the plant research community. A realistic tabulation of plant genomic resources is included for a less laborious and accurate candidate gene discovery in basic plant research and improvement strategies.

Using the Arabidopsis Information Resource (TAIR) to Find Information About Arabidopsis Genes

The Arabidopsis Information Resource (TAIR; http://arabidopsis.org) is a comprehensive web resource of Arabidopsis biology for plant scientists. TAIR curates and integrates information about genes, proteins, gene function, orthologs, gene expression, mutant phenotypes, biological materials such as clones and seed stocks, genetic markers, genetic and physical maps, genome organization, images of mutant plants, protein sub-cellular localizations, publications, and the research community. The various data types are extensively interconnected and can be accessed through a variety of web-based search and display tools. This article primarily focuses on some basic methods for searching, browsing, visualizing, and analyzing information about Arabidopsis genes and genomes. Additionally, we describe how members of the community can share data via JBrowse and the Generic Online Annotation Submission Tool (GOAT) in order to make their published research more accessible and visible. © 2022 Wiley Periodicals LLC. Basic Protocol 1: TAIR homepage, sitemap, and navigation Basic Protocol 2: Finding comprehensive information about Arabidopsis genes Basic Protocol 3: Using the Arabidopsis genome browser: JBrowse Basic Protocol 4: Using the Gene Ontology annotations for gene discovery and gene function analysis Basic Protocol 5: Using gene lists to download bulk datasets Basic Protocol 6: Using TAIR's analysis tools to find short sequences and motifs Basic Protocol 7: Using the TAIR generic online annotation tool (GOAT) to submit functional annotations for Arabidopsis (or any other species) genes Basic Protocol 8: Using PhyloGenes to visualize gene families and predict functions Basic Protocol 9: Using TAIR to browse Arabidopsis literature Basic Protocol 10: Using the synteny viewer to find and display syntenic regions from Arabidopsis and other plant species.

Testing the association of relative growth rate and adaptation to climate across natural ecotypes of Arabidopsis

Ecophysiologists have reported a range of relationships, including intrinsic trade-offs across and within species between plant relative growth rate in high resource conditions (RGR) vs adaptation to tolerate cold or arid climates, arising from trait-based mechanisms. Few studies have considered ecotypes within a species, in which the lack of a trade-off would contribute to a wide species range and resilience to climate change. For 15 ecotypes of Arabidopsis thaliana in a common garden we tested for associations between RGR vs adaptation to cold or dry native climates and assessed hypotheses for its mediation by 15 functional traits. Ecotypes native to warmer, drier climates had higher leaf density, leaf mass per area, root mass fraction, nitrogen per leaf area and carbon isotope ratio, and lower osmotic potential at full turgor. Relative growth rate was statistically independent of the climate of the ecotype native range and of individual functional traits. The decoupling of RGR and cold or drought adaptation in Arabidopsis is consistent with multiple stress resistance and avoidance mechanisms for ecotypic climate adaptation and would contribute to the species' wide geographic range and resilience as the climate changes.

A metabolic, phylogenomic and environmental atlas of diatom plastid transporters from the model species Phaeodactylum

Diatoms are an important group of algae, contributing nearly 40% of total marine photosynthetic activity. However, the specific molecular agents and transporters underpinning the metabolic efficiency of the diatom plastid remain to be revealed. We performed in silico analyses of 70 predicted plastid transporters identified by genome-wide searches of Phaeodactylum tricornutum. We considered similarity with Arabidopsis thaliana plastid transporters, transcriptional co-regulation with genes encoding core plastid metabolic pathways and with genes encoded in the mitochondrial genomes, inferred evolutionary histories using single-gene phylogeny, and environmental expression trends using Tara Oceans meta-transcriptomics and meta-genomes data. Our data reveal diatoms conserve some of the ion, nucleotide and sugar plastid transporters associated with plants, such as non-specific triose phosphate transporters implicated in the transport of phosphorylated sugars, NTP/NDP and cation exchange transporters. However, our data also highlight the presence of diatom-specific transporter functions, such as carbon and amino acid transporters implicated in intricate plastid-mitochondria crosstalk events. These confirm previous observations that substrate non-specific triose phosphate transporters (TPT) may exist as principal transporters of phosphorylated sugars into and out of the diatom plastid, alongside suggesting probable agents of NTP exchange. Carbon and amino acid transport may be related to intricate metabolic plastid-mitochondria crosstalk. We additionally provide evidence from environmental meta-transcriptomic/meta- genomic data that plastid transporters may underpin diatom sensitivity to ocean warming, and identify a diatom plastid transporter (J43171) whose expression may be positively correlated with temperature.

Investigation of Brassica and its relative genomes in the post-genomics era

The Brassicaceae family includes many economically important crop species, as well as cosmopolitan agricultural weed species. In addition, Arabidopsis thaliana, a member of this family, is used as a molecular model plant species. The genus Brassica is mesopolyploid, and the genus comprises comparatively recently originated tetrapolyploid species. With these characteristics, Brassicas have achieved the commonly accepted status of model organisms for genomic studies. This paper reviews the rapid research progress in the Brassicaceae family from diverse omics studies, including genomics, transcriptomics, epigenomics, and three-dimensional (3D) genomics, with a focus on cultivated crops. The morphological plasticity of Brassicaceae crops is largely due to their highly variable genomes. The origin of several important Brassicaceae crops has been established. Genes or loci domesticated or contributing to important traits are summarized. Epigenetic alterations and 3D structures have been found to play roles in subgenome dominance, either in tetraploid Brassica species or their diploid ancestors. Based on this progress, we propose future directions and prospects for the genomic investigation of Brassicaceae crops.

Genome-wide analysis of sulfur-encoding biosynthetic genes in rice (Oryza sativa L.) with Arabidopsis as the sulfur-dependent model plant

Sulfur is an essential element required for plant growth and development, physiological processes and stress responses. Sulfur-encoding biosynthetic genes are involved in the primary sulfur assimilation pathway, regulating various mechanisms at the gene, cellular and system levels, and in the biosynthesis of sulfur-containing compounds (SCCs). In this study, the SCC-encoding biosynthetic genes in rice were identified using a sulfur-dependent model plant, the Arabidopsis. A total of 139 AtSCC from Arabidopsis were used as reference sequences in search of putative rice SCCs. At similarity index > 30%, the similarity search against Arabidopsis SCC query sequences identified 665 putative OsSCC genes in rice. The gene synteny analysis showed a total of 477 syntenic gene pairs comprised of 89 AtSCC and 265 OsSCC biosynthetic genes in Arabidopsis and rice, respectively. Phylogenetic tree of the collated (AtSCCs and OsSCCs) SCC-encoding biosynthetic genes were divided into 11 different clades of various sizes comprised of branches of subclades. In clade 1, nearing equal representation of OsSCC and AtSCC biosynthetic genes imply the most ancestral lineage. A total of 25 candidate Arabidopsis SCC homologs were identified in rice. The gene ontology enrichment analysis showed that the rice-Arabidopsis SCC homologs were significantly enriched in the following terms at false discovery rate (FDR) < 0.05: (i) biological process; sulfur compound metabolic process and organic acid metabolic processes, (ii) molecular function; oxidoreductase activity, acting on paired donors with incorporation or reduction of molecular oxygen and (iii) KEGG pathway; metabolic pathways and biosynthesis of secondary metabolites. At less than five duplicated blocks of separation, no tandem duplications were observed among the SCC biosynthetic genes distributed in rice chromosomes. The comprehensive rice SCC gene description entailing syntenic events with Arabidopsis, motif distribution and chromosomal mapping of the present findings offer a foundation for rice SCC gene functional studies and advanced strategic rice breeding.

Two wrongs make a right: heat stress reversion of a male-sterile Brassica napus line

Male-sterile lines play important roles in plant breeding to obtain hybrid vigour. The male sterility Lembke (MSL) system is a thermosensitive genic male sterility system of Brassica napus and is one of the main systems used in European rapeseed breeding. Interestingly, the MSL system shows high similarity to the 9012AB breeding system from China, including the ability to revert to fertile in high temperature conditions. Here we demonstrate that the MSL system is regulated by the same restorer of fertility gene BnaC9-Tic40 as the 9012AB system, which is related to the translocon at the inner envelope membrane of chloroplasts 40 (TIC40) from Arabidopsis. The male sterility gene of the MSL system was also identified to encode a chloroplast-localized protein which we call BnChimera; this gene shows high sequence similarity to the sterility gene previously described for the 9012AB system. For the first time, a direct protein interaction between BnaC9-Tic40 and the BnChimera could be demonstrated. In addition, we identify the corresponding amino acids that mediate this interaction and suggest how BnaC9-Tic40 acts as the restorer of fertility. Using an RNA-seq approach, the effects of heat treatment on the male fertility restoration of the C545 MSL system line were investigated. These data demonstrate that many pollen developmental pathways are affected by higher temperatures. It is hypothesized that heat stress reverses the male sterility via a combination of slower production of cell wall precursors in plastids and a slower flower development, which ultimately results in fertile pollen. The potential breeding applications of these results are discussed regarding the use of the MSL system in producing thermotolerant fertile plants.

Genome-wide analysis of AAAG and ACGT cis-elements in Arabidopsis thaliana reveals their involvement with genes downregulated under jasmonic acid response in an orientation independent manner

Cis-regulatory elements are regions of noncoding DNA that regulate the transcription of neighboring genes. The study of cis-element architecture that functions in transcription regulation are essential. AAAG and ACGT are a class of cis-regulatory elements, known to interact with Dof and bZIP transcription factors respectively, and are known to regulate the expression of auxin response, gibberellin response, floral development, light response, seed storage proteins genes, biotic and abiotic stress genes in plants. Analysis of the frequency of occurrence of AAAG and ACGT motifs from varying spacer lengths (0–30 base pair) between these 2 motifs in both possible orientations—AAAG _(N) ACGT and ACGT _(N) AAAG, in the promoters and genome of Arabidopsis thaliana which indicated preferred orientation of AAAG _(N) ACGT over ACGT _(N) AAAG across the genome and in promoters. Further, microarray analysis revealed the involvement of these motifs in the genes downregulated under jasmonic acid response in an orientation-independent manner. These results were further confirmed by the transient expression studies with promoter-reporter cassettes carrying AAAG and ACGT motifs in both orientations. Furthermore, cluster analysis on genes with AAAG _(N) ACGT and ACGT _(N) AAAG motifs orientations revealed clusters of genes to be involved in ABA signaling, transcriptional regulation, DNA binding, and metal ion binding. These findings can be utilized in designing synthetic promoters for the development of stress-tolerant transgenic plants and also provides an insight into the roles of these motifs in transcriptional regulation.

Genome-Wide Characterization of DGATs and Their Expression Diversity Analysis in Response to Abiotic Stresses in Brassica napus

Triacylglycerol (TAG) is the most important storage lipid for oil plant seeds. Diacylglycerol acyltransferases (DGATs) are a key group of rate-limiting enzymes in the pathway of TAG biosynthesis. In plants, there are three types of DGATs, namely, DGAT1, DGAT2 and DGAT3. Brassica napus, an allotetraploid plant, is one of the most important oil plants in the world. Previous studies of Brassica napus DGATs (BnaDGATs) have mainly focused on BnaDGAT1s. In this study, four DGAT1s, four DGAT2s and two DGAT3s were identified and cloned from B. napus ZS11. The analyses of sequence identity, chromosomal location and collinearity, phylogenetic tree, exon/intron gene structures, conserved domains and motifs, and transmembrane domain (TMD) revealed that BnaDGAT1, BnaDGAT2 and BnaDGAT3 were derived from three different ancestors and shared little similarity in gene and protein structures. Overexpressing BnaDGATs showed that only four BnaDGAT1s can restore TAG synthesis in yeast H1246 and promote the accumulation of fatty acids in yeast H1246 and INVSc1, suggesting that the three BnaDGAT subfamilies had greater differentiation in function. Transcriptional analysis showed that the expression levels of BnaDGAT1s, BnaDGAT2s and BnaDGAT3s were different during plant development and under different stresses. In addition, analysis of fatty acid contents in roots, stems and leaves under abiotic stresses revealed that P starvation can promote the accumulation of fatty acids, but no obvious relationship was shown between the accumulation of fatty acids with the expression of BnaDGATs under P starvation. This study provides an extensive evaluation of BnaDGATs and a useful foundation for dissecting the functions of BnaDGATs in biochemical and physiological processes.

Plant cytoplasmic ribosomal proteins: an update on classification, nomenclature, evolution and resources

Standardized naming systems are essential to integrate and unify distinct research fields, and to link multi-species data within and across kingdoms. We conducted a comprehensive survey of cytoplasmic ribosomal proteins (CRPs) in the dicot model Arabidopsis thaliana and the monocot model rice, noting that the standardized naming system has not been widely adopted in the plant community. We generated a database linking the old classical names to their updated and compliant names. We also explored the sequences, molecular evolution, and structural and functional characteristics of all plant CRP families, emphasizing evolutionarily conserved and plant-specific features through cross-kingdom comparisons. Unlike fungal CRP paralogs that were mainly created by whole-genome duplication (WGD) or retroposition under a concerted evolution mode, plant CRP genes evolved primarily through both WGD and tandem duplications in a rapid birth-and-death process. We also provide a web-based resource (http://www.plantcrp.cn/) with the aim of sharing the latest knowledge on plant CRPs and facilitating the continued development of a standardized framework across the entire community.

Innovation and Emerging Roles of Populus trichocarpa TEOSINTE BRANCHED1/CYCLOIDEA/PROLIFERATING CELL FACTOR Transcription Factors in Abiotic Stresses by Whole-Genome Duplication

The TEOSINTE BRANCHED1/CYCLOIDEA/PROLIFERATING CELL FACTOR (TCP) family proteins are plant-specific transcription factors that have been well-acknowledged for designing the architectures of plant branch, shoot, and inflorescence. However, evidence for their innovation and emerging role in abiotic stress has been lacking. In this study, we identified a total of 36 TCP genes in Populus trichocarpa, 50% more than that in Arabidopsis (i.e., 24). Comparative intra-genomes showed that such significant innovation was mainly due to the most recent whole genome duplication (rWGD) in Populus lineage around Cretaceous-Paleogene (K-Pg) boundary after the divergence from Arabidopsis. Transcriptome analysis showed that the expressions of PtrTCP genes varied among leaf, stem, and root, and they could also be elaborately regulated by abiotic stresses (e.g., cold and salt). Moreover, co-expression network identified a cold-associated regulatory module including PtrTCP31, PtrTCP10, and PtrTCP36. Of them, PtrTCP10 was rWGD-duplicated from PtrTCP31 and evolved a strong capability of cold induction, which might suggest a neofunctionalization of PtrTCP genes and contribute to the adaptation of Populus lineage during the Cenozoic global cooling. Evidentially, overexpression of PtrTCP10 into Arabidopsis increased freezing tolerance and salt susceptibility. Integrating co-expression network and cis-regulatory element analysis confirmed that PtrTCP10 can regulate the well-known cold- and salt-relevant genes (e.g., ZAT10, GolS2, and SOS1), proving that PtrTCP10 is an evolutionary innovation in P. trichocarpa response to environmental changes. Altogether, our results provide evidence of the rWGD in P. trichocarpa responsible for the innovation of PtrTCP genes and their emerging roles in environmental stresses.

Innovation and Emerging Roles of Populus trichocarpa TEOSINTE BRANCHED1/CYCLOIDEA/PROLIFERATING CELL FACTOR Transcription Factors in Abiotic Stresses by Whole-Genome Duplication

The TEOSINTE BRANCHED1/CYCLOIDEA/PROLIFERATING CELL FACTOR (TCP) family proteins are plant-specific transcription factors that have been well-acknowledged for designing the architectures of plant branch, shoot, and inflorescence. However, evidence for their innovation and emerging role in abiotic stress has been lacking. In this study, we identified a total of 36 TCP genes in Populus trichocarpa, 50% more than that in Arabidopsis (i.e., 24). Comparative intra-genomes showed that such significant innovation was mainly due to the most recent whole genome duplication (rWGD) in Populus lineage around Cretaceous-Paleogene (K-Pg) boundary after the divergence from Arabidopsis. Transcriptome analysis showed that the expressions of PtrTCP genes varied among leaf, stem, and root, and they could also be elaborately regulated by abiotic stresses (e.g., cold and salt). Moreover, co-expression network identified a cold-associated regulatory module including PtrTCP31, PtrTCP10, and PtrTCP36. Of them, PtrTCP10 was rWGD-duplicated from PtrTCP31 and evolved a strong capability of cold induction, which might suggest a neofunctionalization of PtrTCP genes and contribute to the adaptation of Populus lineage during the Cenozoic global cooling. Evidentially, overexpression of PtrTCP10 into Arabidopsis increased freezing tolerance and salt susceptibility. Integrating co-expression network and cis-regulatory element analysis confirmed that PtrTCP10 can regulate the well-known cold- and salt-relevant genes (e.g., ZAT10, GolS2, and SOS1), proving that PtrTCP10 is an evolutionary innovation in P. trichocarpa response to environmental changes. Altogether, our results provide evidence of the rWGD in P. trichocarpa responsible for the innovation of PtrTCP genes and their emerging roles in environmental stresses.

The novel activity of Argonautes in intron splicing: A transcriptome-wide survey in plants

The importance of the evolutionarily conserved Argonaute (AGO) proteins has been well recognized for their involvement in the RNA interference pathways. Recent discoveries in animals demonstrated that AGOs also participate in alternative splicing (AS). Motivated by the question whether the AGO proteins are also functional in RNA splicing in plants, we searched for the introns excised through an AGO-dependent manner in Arabidopsis (Arabidopsis thaliana). RNA sequencing (RNA-seq) data analysis uncovered hundreds of the introns up- or down-regulated in the ago1 and ago4 mutants, respectively. For different genes, AGOs might play either a positive or a negative role in intron excision, which was further validated by reverse transcription-polymerase chain reaction (RT-PCR). Some introns were specifically regulated by one of the AGO proteins, while some were regulated by both AGOs. Besides, a large portion of the AGO-dependent introns were organ-specifically regulated. RNA immunoprecipitation combined with high-throughput sequencing (RIP-seq) revealed that both AGOs preferentially bound to the intronic regions, supporting their high intron binding affinities. Immunoprecipitation followed by mass spectrometry (IP-MS) was performed to identify the proteins potentially interacting with the two AGOs. Six novel interactors (two interacting with AGO1 and four with both AGOs) involved in mRNA binding were uncovered, which might facilitate AGO-intron recognition. Analysis of the RNA-seq data from the rice (Oryza sativa) ago18 mutants revealed that hundreds of the introns were expressed in an AGO18-dependent manner. In summary, our results point to the novel role of the plant AGOs in intron splicing, paving a way for further studies on the mechanisms underlying AGO-mediated RNA splicing.

BRAD V3.0: an upgraded Brassicaceae database

The Brassicaceae Database (BRAD version 3.0, BRAD V3.0; http://brassicadb.cn) has evolved from the former Brassica Database (BRAD V2.0), and represents an important community portal hosting genome information for multiple Brassica and related Brassicaceae plant species. Since the last update in 2015, the complex genomes of numerous Brassicaceae species have been decoded, accompanied by many omics datasets. To provide an up-to-date service, we report here a major upgrade of the portal. The Model-View-ViewModel (MVVM) framework of BRAD has been re-engineered to enable easy and sustainable maintenance of the database. The collection of genomes has been increased to 26 species, along with optimization of the user interface. Features of the previous version have been retained, with additional new tools for exploring syntenic genes, gene expression and variation data. In the 'Syntenic Gene @ Subgenome' module, we added features to view the sequence alignment and phylogenetic relationships of syntenic genes. New modules include 'MicroSynteny' for viewing synteny of selected fragment pairs, and 'Polymorph' for retrieval of variation data. The updated BRAD provides a substantial expansion of genomic data and a comprehensive improvement of the service available to the Brassicaceae research community.

Identification of WRKY transcription factors responding to abiotic stresses in Brassica napus L

A total of 278 BnWRKYs were identified and analyzed. Ectopic expression of BnWRKY149 and BnWRKY217 suggests that they function in the ABA signaling pathway. WRKY transcription factors play an important role in plant development, however, their function in Brassica napus L. abiotic stress response is still unclear. In this study, a total of 278 BnWRKY transcription factors were identified from the B. napus genome data, and they were subsequently distributed in three main groups. The protein motifs and classification of BnWRKY transcription factors were analyzed, and the locations of their corresponding encoding genes were mapped on the chromosomes of B. napus. Transcriptome analysis of rapeseed seedlings exposed to drought, salt, heat, cold and abscisic acid treatment revealed that 99 BnWRKYs responded to at least one of these stresses. The expression profiles of 12 BnWRKYs were examined with qPCR and the result coincided with RNA-seq analysis. Two genes of interest, BnWRKY149 and BnWRKY217 (homologs of AtWRKY40), were overexpressed in Arabidopsis, and the corresponding proteins were located to the nucleus. Transgene plants of BnWRKY149 and BnWRKY217 were less sensitive to ABA than Arabidopsis Col-0 plants, suggesting they might play important roles in the responses of rapeseed to abiotic stress.

The Responses of the Lipoxygenase Gene Family to Salt and Drought Stress in Foxtail Millet (Setaria italica)

Plant lipoxygenases (LOXs), a kind of non-heme iron-containing dioxygenases, participate plant physiological activities (especially in response to biotic and abiotic stresses) through oxidizing various lipids. However, there was few investigations on LOXs in foxtail millet (Setaria italica). In this study, we identified the LOX gene family in foxtail millet, and divided the total 12 members into three sub-families on the basis of their phylogenetic relationships. Under salt and drought stress, LOX genes showed different expression patterns. Among them, only SiLOX7 showed up-regulated expression in Yugu1 (YG1) and Qinhuang2 (QH2), two stress-tolerant varieties, indicating that SiLOX7 may play an important role in responses to abiotic stress. Our research provides a basis for further investigation of the role of LOX genes in the adaptation to abiotic stresses and other possible biological functions in foxtail millet.

Evaluation of methods for plant genomic DNA sequence analysis without DNA and PCR product purification

Genome-editing technologies are widely used to characterize gene functions and improve the features of agricultural plants. Although sequence analysis of gene editing target DNA is the most reliable method of screening gene-edited plants, the current DNA sequence analysis methods are time consuming and labor intensive because they include genomic DNA and polymerase chain reaction (PCR) product purification. In this study, seven methods were performed for sequence analysis of plant genomic DNA with and/or without genomic DNA and PCR product purification. Consequently, good-quality sequencing chromatograms were obtained using all methods. Results showed that the partial genomic DNA sequence of Nicotiana benthamiana and Arabidopsis thaliana could be sufficiently analyzed without plant genomic DNA and PCR product purification. Furthermore, screening of gene-edited N. benthamiana was successful using the present methods. Therefore, the tested methods could reduce the time, simplify the workflow of plant gene analysis, and help in screening gene-edited plants.

Comparing Early Transcriptomic Responses of 18 Soybean (Glycine max) Genotypes to Iron Stress

Iron deficiency chlorosis (IDC) is an abiotic stress that negatively affects soybean (Glycine max [L.] Merr.) production. Much of our knowledge of IDC stress responses is derived from model plant species. Gene expression, quantitative trait loci (QTL) mapping, and genome-wide association studies (GWAS) performed in soybean suggest that stress response differences exist between model and crop species. Our current understanding of the molecular response to IDC in soybeans is largely derived from gene expression studies using near-isogenic lines differing in iron efficiency. To improve iron efficiency in soybeans and other crops, we need to expand gene expression studies to include the diversity present in germplasm collections. Therefore, we collected 216 purified RNA samples (18 genotypes, two tissue types [leaves and roots], two iron treatments [sufficient and deficient], three replicates) and used RNA sequencing to examine the expression differences of 18 diverse soybean genotypes in response to iron deficiency. We found a rapid response to iron deficiency across genotypes, most responding within 60 min of stress. There was little evidence of an overlap of specific differentially expressed genes, and comparisons of gene ontology terms and transcription factor families suggest the utilization of different pathways in the stress response. These initial findings suggest an untapped genetic potential within the soybean germplasm collection that could be used for the continued improvement of iron efficiency in soybean.