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Biology subjects

Takagi, H.

Publications and source records attributed to Takagi, H..

At least 19 recordsLinked to original sources

A cyclo-DOPA 6-O-glucosyltransferase-mediated route for gomphrenin I biosynthesis in Basella alba and Gomphrena globosa

O_LIBetacyanins are red pigments characteristic of Caryophyllales and show considerable structural diversity, yet the enzymatic basis underlying 6-O-glucosylated betacyanins such as gomphrenin I has remained unclear. In particular, how alternative glucosylation patterns contribute to betacyanin diversification is poorly understood. C_LIO_LIHere, we identified cyclo-DOPA glucosyltransferases from Basella alba and Gomphrena globosa and examined their roles in gomphrenin I biosynthesis using transient expression assays and tobacco BY-2 cell systems. Phylogenetic analyses, structural modelling and site-directed mutagenesis were employed to investigate their functional and structural characteristics. C_LIO_LIBacDOPA5/6GTs catalysed both 5-O- and 6-O-glucosylation of cyclo-DOPA, leading to the production of betanin and gomphrenin I, whereas GgcDOPA6GT specifically mediated gomphrenin I formation. These enzymes belong to distinct subclades within the cDOPA-GT family, and mutational analyses demonstrated essential roles for conserved histidine residues and an -helical region adjacent to the catalytic site. C_LIO_LIThermal stability analyses further showed that gomphrenin I is more thermally stable than betanin, likely due to the formation of an intramolecular hydrogen bond. Together, these results reveal an additional cDOPA6GT-mediated route for gomphrenin I biosynthesis and provide insight into the diversification and functional specialization of betacyanins, linking the position of glucosylation to pigment stability and biochemical properties. C_LI

plant biology↗

An evolutionary landscape of sesame: chromosomal variation, allopolyploid speciation and metabolic specialization.

Sesame (Sesamum indicum) is one of the earliest domesticated oilseed crops and is valued for antioxidant lignans that stabilize oil quality. However, the genomic and evolutionary history of the genus Sesamum, including the origin of its allotetraploid relative S. radiatum and the diversification of lignan metabolism, remains poorly understood owing to limited chromosome-scale genomic resources. Here we present chromosome-level genome assemblies for three wild Sesamum species, two Ceratotheca species and a Japanese sesame cultivar to reconstruct genome and karyotype evolution across the Sesamum-Ceratotheca complex. Comparative analyses show that the derived x=16 lineage originated from an ancestral x=13 karyotype through chromosome fission, fusion and translocation, whereas another x=13 lineage underwent extensive restructuring associated with retrotransposon expansion. Phylogenomics places Ceratotheca within the x=16 Sesamum clade and reveals that S. radiatum originated through hybridization involving a C. sesamoides-like ancestor. The antioxidative lignan gene CYP92B14 was reintroduced via the BB progenitor, linking hybridization with restoration of oil-stabilizing metabolism during sesame evolution.

genomics↗

HDA19-mediated deacetylation of histone H3.3 lysine 27 and 36 regulates plant sensitivity to salt stress

Plants survive extreme environments through rapid chromatin reprogramming, yet the epigenetic marks that confer stress resilience remain poorly understood. Histone deacetylase HDA19 is a key epigenetic regulator in Arabidopsis, and hda19-deficient mutants display tolerance to multiple abiotic stresses, including drought, heat, and salinity. Using lysine acetylome profiling, we identified a non-canonical K27/K36 di-acetylation mark on histone H3.3, among nine H3 variants, as a specific substrate of HDA19. Under salinity stress, this mark decreased in wild-type plants but increased in hda19 mutants, while other known H3 modifications were similarly affected in both genotypes. Mimicking constitutive di-acetylation of H3.3 K27/K36 through lysine-to-glutamine substitutions promoted accumulation of stress-responsive late embryogenesis abundant (LEA) proteins and conferred salinity tolerance in seedlings, phenocopying hda19 mutants. Furthermore, generating the lea7-1/lea29-1/rab18-1 triple mutant abolished hda19-dependent salinity tolerance, confirming the LEA proteins role downstream of HDA19. Our findings demonstrate that H3.3 K27/K36 di-acetylation, modulated by HDA19, drives LEA protein accumulation and enables plants to withstand environmental stress, revealing a previously unknown core mechanism of plant stress resilience. Significance statementHistone acetylation is crucial for regulating chromatin states and transcription, yet the specific histone codes controlled by histone deacetylases and acetyltransferases during plant stress acclimation remain unclear. Arabidopsis mutants lacking histone deacetylase 19 show enhanced tolerance to drought, heat, and salinity. Using acetylome profiling and genetic analyses, we identify a previously unknown di-acetylation of histone H3.3 at lysines 27 and 36 as a key epigenetic switch activating late embryogenesis abundant proteins essential for salt tolerance in seedlings. This discovery reveals a novel mechanism linking histone H3.3 K27/K36 di-acetylation to stress-resilient protein accumulation, offering new insights into epigenetic control of plant stress responses and informing strategies to improve crop resilience under climate change.

plant biology↗

Multiple ammonium transporters in fission yeast are coordinated by transcriptional and localization regulation in response to nitrogen starvation

Ammonium is a preferred nitrogen source for microorganisms. We investigated the regulation of ammonium transporters Amt1, Amt2, and Amt3 in the fission yeast Schizosaccharomyces pombe. Expression of the amt1+ gene increases under nitrogen starvation as well as in the TORC1-deficient mutant tor2-287, suggesting the negative regulation of amt1+ by TORC1. This regulation depends on the GATA transcription factor Gaf1, whose phosphorylation is regulated by Ppe1 and PP2A phosphatases. Ppe1 is required for the nuclear accumulation of Gaf1, partly contributing to the controlled expression of amt1+. On the other hand, PP2A phosphatase is essential for the amt1+ induction upon starvation, indicating distinct roles for Ppe1 and PP2A in Gaf1 regulation. Nitrogen starvation also promotes the plasma membrane translocation of Amt1 and Amt2 in a manner dependent on the Tsc-Rhb1 pathway. Intriguingly, the amt1{Delta} amt2{Delta} tsc{Delta} mutant is more sensitive to low-ammonium conditions than the amt1{Delta} amt2{Delta} amt3{Delta} triple mutant. Thus, there may be an unidentified ammonium transporter whose plasma membrane localization is also dependent on the Tsc-Rhb1 pathway.

cell biology↗

Live sports spectating promotes oxytocin dynamics and heart rate synchrony in casual fans

Oxytocin has been proposed as a pharmacological target for social dysfunction. However, clinical trials of exogenous oxytocin have yielded modest and inconsistent benefits, highlighting the need for naturalistic, non-pharmacological approaches that recruit endogenous oxytocin. This prospective observational field study examined whether live sports spectating in a modest collegiate setting engages endogenous oxytocin and heart rate synchrony, and how these processes relate to social bonding. Sixty casual spectators at two university basketball games provided salivary samples for oxytocin and cortisol and completed psychological questionnaires before the game, at halftime, and after the game, while heart rate was continuously recorded. Oxytocin dynamics were baseline dependent: individuals with low pre-game oxytocin showed clear increases during spectating, whereas those with high pre-game oxytocin maintained elevated concentrations; across both groups, cortisol decreased and the oxytocin-to-cortisol ratio increased, indicating a shift toward an oxytocin-dominant, low-stress hormonal profile. Live spectating also enhanced heart rate synchrony between spectators, and higher oxytocin levels and stronger synchrony were associated with greater enjoyment, stronger unity with players and fellow fans, higher flow, and stronger intention to revisit. Mediation analyses indicated that perceived unity mediated links between physiological responses and experiential outcomes. These findings identify coordinated oxytocin dynamics and physiological synchrony as candidate mechanisms through which live sports spectating can foster social connection and positive psychological states in everyday, low-stakes settings. Live sports events may represent a simple, scalable non-pharmacological approach to engaging oxytocin-related systems and interpersonal synchrony to promote social connection in everyday life.

neuroscience↗

Genomic prediction models based on a large-scale recombinant population allow quick breeding of high-yield rice

Rapid development of cultivars with optimal genome-wide allele combinations is essential for addressing agricultural challenges. However, constructing desired genotypes through conventional cross-breeding requires many generations, calling for a more efficient methodology. Here, we present a rapid breeding strategy that combines a large-scale recombinant population as starting material with interpretable genomic prediction models trained on that population. This approach enables efficient construction of target genotypes optimized for multiple traits in cultivars. To validate our strategy in rice (Oryza sativa), we established a nested association mapping population of 2,787 recombinant inbred lines derived from an elite cultivar 'Hitomebore' and 19 diverse donors. We built highly accurate genomic prediction models using this population. We then used the models to estimate haplotype-specific effects and account for trade-offs among yield-related traits, and selected optimal lines and designed breeding schemes. Crossbreeding based on these schemes produced rice lines with the target genotypes for multiple yield-related traits, supporting the predicted effects and validating the effectiveness of our strategy. This genomic breeding approach provides a general framework for rapidly breeding cultivars able to meet the challenges posed by a changing environment.

genetics↗

Evolution and functioning of an X-A balance sex determination system in hops

Chromosomal sex determining systems with male heterogamety include actively male-determining-Y and X-A balance systems, both of which are found in animals and plants. The sex-determining genes have been identified in several active-Y plant systems, but the evolution and functioning of X-A balance systems remains mysterious. To study this, we sequenced and compared the genomes of two hop species. The evolution of the hop X-A balance system involved an ancient recombination suppression event across a large X chromosome region shared by both species. In one species, an autosome fused to this ancestral sex chromosome, and recombination was subsequently suppressed again. The two evolutionary strata created in this neo-X have degenerated to different degrees, and evolved correspondingly different dosage compensation levels that correlate with histone modification patterns. Finally, we identified an X-specific ETR1-like ethylene receptor in the ancestral X region. Its dosage may affect sex determination, as part of the counting mechanism of this X-A balance system. One sentence summaryBased on whole genome sequences of the cultivated hop, Humulus lupulus, and its wild relative H. japonicus, we describe the evolution of sex chromosomal regions, three of which that evolved region-specific dosage compensation, and identify a candidate gene involved in their X-A balance sex determining system.

evolutionary biology↗

A florigen-expressing subpopulation of companion cells expresses other small proteins and reveals a nitrogen-sensitive FT repressor

The precise onset of flowering is crucial to ensure successful plant reproduction. The gene FLOWERING LOCUS T (FT) encodes florigen, a mobile signal produced in leaves that initiates flowering at the shoot apical meristem. In response to seasonal changes, FT is induced in phloem companion cells located in distal leaf regions. Thus far, a detailed molecular characterization of the FT-expressing cells has been lacking. Here, we used bulk nuclei RNA-seq and single nuclei RNA (snRNA)-seq to investigate gene expression in FT-expressing cells and other phloem companion cells. Our bulk nuclei RNA-seq demonstrated that FT-expressing cells in cotyledons and true leaves showed differences especially in FT repressor genes. Within the true leaves, our snRNA-seq analysis revealed that companion cells with high FT expression form a unique cluster in which many genes involved in ATP biosynthesis are highly upregulated. The cluster also expresses other genes encoding small proteins, including the flowering and stem growth inducer FPF1-LIKE PROTEIN 1 (FLP1) and the anti-florigen BROTHER OF FT AND TFL1 (BFT). In addition, we found that the promoters of FT and the genes co-expressed with FT in the cluster were enriched for the consensus binding motifs of NITRATE-INDUCIBLE GARP-TYPE TRANSCRIPTIONAL REPRESSOR 1 (NIGT1). Overexpression of the paralogous NIGT1.2 and NIGT1.4 repressed FT expression and significantly delayed flowering under nitrogen-rich conditions, consistent with NIGT1s acting as nitrogen-dependent FT repressors. Taken together, our results demonstrate that major FT-expressing cells show a distinct expression profile that suggests that these cells may produce multiple systemic signals to regulate plant growth and development.

plant biology↗

Florigen-producing cells express FPF1-LIKE PROTEIN 1 that accelerates flowering and stem growth in long days with sunlight red/far-red ratio in Arabidopsis

Seasonal changes in spring induce flowering by expressing the florigen, FLOWERING LOCUS T (FT), in Arabidopsis. FT is expressed in unique phloem companion cells with unknown characteristics. The question of which genes are co-expressed with FT and whether they have roles in flowering remains elusive. Through tissue-specific translatome analysis, we discovered that under long-day conditions with the natural sunlight red/far-red ratio, the FT-producing cells express a gene encoding FPF1-LIKE PROTEIN 1 (FLP1). The master FT regulator, CONSTANS (CO), controls FLP1 expression, suggesting FLP1s involvement in the photoperiod pathway. FLP1 promotes early flowering independently of FT, is active in the shoot apical meristem, and induces the expression of SEPALLATA 3 (SEP3), a key E-class homeotic gene. Unlike FT, FLP1 facilitates inflorescence stem elongation. Our cumulative evidence indicates that FLP1 may act as a mobile signal. Thus, FLP1 orchestrates floral initiation together with FT and promotes inflorescence stem elongation during reproductive transitions.

plant biology↗

Impact of rice GENERAL REGULATORY FACTOR14h (GF14h) on low-temperature seed germination and its application to breeding

Direct seeding is employed to circumvent the labor-intensive process of rice (Oryza sativa) transplantation, but this approach requires varieties with vigorous low-temperature germination (LTG) when sown in cold climates. To investigate the genetic basis of LTG, we identified the quantitative trait locus (QTL) qLTG11 from rice variety Arroz da Terra, which shows rapid seed germination at lower temperatures, using QTL-seq. We delineated the candidate region to a 52-kb interval containing GENERAL REGULATORY FACTOR14h (GF14h) gene, which is expressed during seed germination. The Arroz da Terra GF14h allele encodes functional GF14h, whereas Japanese rice variety Hitomebore harbors a 4-bp deletion in the coding region. Knocking out functional GF14h in a near-isogenic line (NIL) carrying the Arroz da Terra allele decreased LTG, whereas overexpressing functional GF14h in Hitomebore increased LTG, indicating that GF14h is the causal gene behind qLTG11. Analysis of numerous Japanese rice accessions revealed that the functional GF14h allele was lost from popular varieties during modern breeding. We generated a NIL in the Hitomebore background carrying a 172-kb genomic fragment from Arroz da Terra including GF14h. The NIL showed superior LTG compared to Hitomebore, with otherwise comparable agronomic traits. The functional GF14h allele from Arroz da Terra represents a valuable resource for direct seeding in cold regions. Author SummaryRice serves as a fundamental crop sustaining over half of the global population. With the rapid growth of the worlds population, it will become increasingly important to improve rice productivity. On the other hand, the aging of rice farmers in Japan has resulted in a constant labor shortage. To address this, direct seeding, in which seeds are sown directly in rice fields without going through the most labor-intensive part of the rice cultivation process, i.e., seedling production and transplanting, has been recommended. However, prevalent elite rice varieties are known to be unsuitable for direct seeding due to their poor seed germination ability under low-temperature conditions. In this study, we show for the first time that GF14h gene from the Portuguese variety Arroz da Terra improves seed germination at low temperatures (LTG). In addition, a novel cross-bred line was generated by introducing the GF14h-containing genomic segment from Arroz da Terra into Hitomebore, a widely cultivated variety in northern Japan. This line is expected to be used as a pre-breeding material to enhance LTG. This study will provide a genetic basis for LTG and contribute to basic and applied research progress.

plant biology↗

Dynamic coordination of the lever-arm swing of human myosin II in thick filaments on actin

Muscle myosins work in motor ensembles and must adapt their power stroke in response to mechanical actions by surrounding motors. Understanding the coordination of power strokes is essential for bridging microscopic molecular functions and macroscopic muscle contractions, but the details of this phenomenon remain elusive. Here we used high-speed atomic force microscopy to visualize the individual dynamics (lever-arm swing) of the myosin head bound to actin in DNA origami-based synthetic thick filaments. We observed spatially local lever-arm coordination, and our three-dimensional numerical model explained how mechanical communication between myosins achieved coordination. In a sarcomere model, the local coordination was spatially periodic and propagated toward the contraction direction. We confirmed that a structural mismatch between myosin head spacing (42.8 nm) and the actin helical pitch (37 nm) caused the coordination while improving contraction speed and energy efficiency. Our findings reveal a key physical basis of efficient muscle contraction.

biophysics↗

Tangled gene-for-gene interactions mediate co-evolution of the rice NLR immune receptor Pik and blast fungus effector proteins

Studies focused solely on single organisms can fail to identify the networks underlying host-pathogen gene-for-gene interactions. Here, we integrate genetic analyses of rice (Oryza sativa, host) and rice blast fungus (Magnaporthe oryzae, pathogen) and uncover a new pathogen recognition specificity of the rice nucleotide-binding domain and leucine-rich repeat protein (NLR) immune receptor Pik, which mediates resistance to M. oryzae expressing the avirulence effector gene AVR-Pik. Rice Piks-1, encoded by an allele of Pik-1, recognizes a previously unidentified effector encoded by the M. oryzae avirulence gene AVR-Mgk1, which is found on a mini-chromosome. AVR-Mgk1 has no sequence similarity to known AVR-Pik effectors, and is prone to deletion from the mini-chromosome mediated by repeated Inago2 retrotransposon sequences. AVR-Mgk1 is detected by Piks-1 and by other Pik-1 alleles known to recognize AVR-Pik effectors; recognition is mediated by AVR-Mgk1 binding to the integrated heavy metal-associated (HMA) domain of Piks-1 and other Pik-1 alleles. Our findings highlight how complex gene-for-gene interaction networks can be disentangled by applying forward genetics approaches simultaneously to the host and pathogen. We demonstrate dynamic co-evolution between an NLR integrated domain and multiple families of effector proteins.

plant biology↗

Mutations in OsRZF1, encoding a zinc-finger protein, causes reduced magnesium uptake in roots and translocation to shoots in rice

Magnesium (Mg) homeostasis is critical for maintaining many biological processes, but little information is available to comprehend the molecular mechanisms regulating Mg concentration in rice (Oryza sativa). To make up for the lack of information, we aimed to identify mutants defective in Mg homeostasis through a forward genetic approach. As a result of the screening of about 3,000 M2 seedlings mutated by ion-beam irradiation, we found a rice mutant that showed reduced Mg content in leaves and slightly increased Mg content in roots. Radiotracer 28Mg experiments showed that this mutant, named low magnesium content 1 (LMGC1), has decreased Mg2+ influx in the root and Mg2+ translocation from root to shoot. The MutMap method identified 7.4 kbp deletion in the LMGC1 genome leading to a loss of two genes. Genome editing using CRISPR-Cas9 further revealed that one of the two lost genes, a gene belonging to RanBP2-type zinc finger family, was the causal gene of the low-Mg phenotype. Considering this gene, named OsRZF1, has never been reported to be involved in ion transport, the phenotype of LMGC1 would be associated with a novel mechanism of Mg homeostasis in plants.

plant biology↗

Genome analyses reveal the hybrid origin of the staple food crop white Guinea yam

White Guinea yam (Dioscorea rotundata) is an important staple tuber crop of West Africa. However, its origin remains unclear. In this study, we re-sequenced 336 accessions of white Guinea yam and compared them with the sequences of the wild Dioscorea species using an improved reference genome sequence of D. rotundata. Our results suggest a hybrid origin of white Guinea yam from crosses between the rainforest wild species D. praehensilis and the savannah-adapted D. abyssinica. We identified a higher genomic contribution from D. abyssinica in the sex chromosome of Guinea yam and an extensive introgression around the SWEETIE gene. Our findings point to a complex domestication scenario for Guinea yam and highlight the importance of wild species as gene donors for improvement of this crop through molecular breeding.

evolutionary biology↗

Genomic stability and adaptation of beer brewing yeasts during serial repitching in the brewery

Ale brewing yeast are the result of admixture between diverse strains of Saccharomyces cerevisiae, resulting in a heterozygous tetraploid that has since undergone numerous genomic rearrangements. As a result, comparisons between the genomes of modern related ale brewing strains show both extensive aneuploidy and mitotic recombination that has resulted in a loss of intragenomic diversity. Similar patterns of intraspecific admixture and subsequent selection for one haplotype have been seen in many domesticated crops, potentially reflecting a general pattern of domestication syndrome between these systems. We set out to explore the evolution of the ale brewing yeast, to understand both polyploid evolution and the process of domestication in the ecologically relevant environment of the brewery. Utilizing a common brewery practice known as repitching, in which yeasts are reused over multiple beer fermentations, we generated population time courses from multiple breweries utilizing similar strains of ale yeast. Applying whole-genome sequencing to the time courses, we have found that the same structural variations in the form of aneuploidy and mitotic recombination of particular chromosomes reproducibly rise to detectable frequency during adaptation to brewing conditions across multiple related strains in different breweries. Our results demonstrate that domestication of ale strains is an ongoing process and will likely continue to occur as modern brewing practices develop.

evolutionary biology↗

High-performance pipeline for MutMap and QTL-seq

Bulked segregant analysis implemented in MutMap and QTL-seq is a powerful and efficient method to identify agronomically important loci. However, the previous pipelines were not user-friendly to install and run. Here, we describe new pipelines for MutMap and QTL-seq. These updated pipelines are approximately 5-8 times faster than the previous pipeline, are easier for novice users to use and can be easily installed through bioconda with all dependencies.

bioinformatics↗

Lumi-Map, a real-time luciferase bioluminescence screen of mutants combined with MutMap, reveals Arabidopsis genes involved in PAMP-triggered immunity

Plants recognize pathogen-associated molecular patterns (PAMPs) to activate PAMP-triggered immunity (PTI). However, our knowledge of PTI signaling remains limited. In this report, we introduce Lumi-Map, a high-throughput platform for identifying causative single nucleotide polymorphisms (SNPs) to studying PTI signaling components. In Lumi-Map, a transgenic reporter plant line is produced that contains a firefly luciferase (LUC) gene driven by a defense gene promoter, which generates luminescence upon PAMP treatment. The line is mutagenized and the mutants with altered luminescence patterns are screened by a high-throughput real-time bioluminescence monitoring system. Selected mutants are subjected to MutMap analysis, a whole genome sequencing (WGS)-based method of rapid mutation identification, to identify the causative SNP responsible for the luminescence pattern change. We generated nine transgenic Arabidopsis reporter lines expressing LUC gene fused to multiple promoter sequences of defense-related genes. These lines generate luminescence upon activation of FLAGELLIN-SENSING 2 (FLS2) by flg22, a PAMP derived from bacterial flagellin. We selected the WRKY29-promoter reporter line to identify mutants in the signaling pathway downstream of FLS2. After screening 24,000 ethylmethanesulfonate (EMS)-induced mutants of the reporter line, we isolated 22 mutants with altered WRKY29 expression upon flg22 treatment (abbreviated as awf mutants). While five flg22-insensitive awf mutants harbored mutations in FLS2 itself, Lumi-Map revealed three genes not previously associated with PTI. Lumi-Map has the potential to identify novel PAMPs and their receptors as well as signaling components downstream of the receptors.

plant biology↗

Arabidopsis SMN2/HEN2, encoding DEAD-box RNA helicase, governs proper expression of the resistance gene SMN1/RPS6 and is involved in dwarf, autoimmune phenotypes of mekk1 and mpk4

In Arabidopsis thaliana, a mitogen-activated protein kinase pathway, MEKK1-MKK1/MKK2-MPK4, is important for basal resistance, and disruption of this pathway results in dwarf, autoimmune phenotypes. To elucidate the complex mechanisms activated by the disruption of this pathway, we have previously developed a mutant screening system based on a dwarf autoimmune line that overexpressed the N-terminal regulatory domain of MEKK1. Here, we report that the second group of mutants, smn2, had defects in the SMN2 gene, encoding a DEAD-box RNA helicase. SMN2 is identical to HEN2, whose function is vital for the nuclear RNA exosome because it provides non-ribosomal RNA specificity for RNA turnover, RNA quality control, and RNA processing. Aberrant SMN1/RPS6 transcripts were detected in smn2 and hen2 mutants. Disease resistance against Pseudomonas syringae pv. tomato DC3000 (hopA1), which is conferred by SMN1/RPS6, was decreased in smn2 mutants, suggesting a functional connection between SMN1/RPS6 and SMN2/HEN2. We produced double mutants mekk1smn2 and mpk4smn2 to determine whether the smn2 mutations suppress the dwarf, autoimmune phenotypes of the mekk1 and mpk4 mutants, as the smn1 mutations do. As expected, the mekk1 and mpk4 phenotypes were suppressed by the smn2 mutations. These results suggested that SMN2 is involved in proper function of SMN1/RPS6. The GO enrichment analysis using RNA-seq data showed that defense genes were downregulated in smn2, suggesting positive contribution of SMN2 to genome-wide expression of defense-related genes. In conclusion, this study provides novel insight into plant immunity via SMN2/HEN2, an essential component of the nuclear RNA exosome.

plant biology↗