Biology subjects

Mohammad, A.

Publications and source records attributed to Mohammad, A..

14 recordsLinked to original sources

bioRxiv2026

Can you run from your worries? The effects of exercise on anxiety-like behaviour and immune signaling in female and male mice

Exercise is a positive health behaviour associated with improved mood. However, the mechanisms underlying the benefits of exercise on affective health are unclear, particularly with respect to type of exercise and sex. Chronic exercise decreases neuroinflammation, which is linked to improvements in mood and anxiety. However, exercise is also a physiological stressor that can transiently upregulate systemic inflammation, and its effects on neuroinflammation are not well understood. This study examined how acute and chronic exercise affect circulating and brain cytokine levels and anxiety-related behaviour in young healthy male and female mice. In Experiment 1, mice were placed on a treadmill for a two-hour bout of moderate exercise. Two hours after exercise, animals were either tested in the open field or euthanized for measurement of cytokines (IL-1{beta}, TNF, IL-2, IL-4, IL-5, IL-6, IL-10, IL-12p70, IFN-{gamma}, KC/GRO). In Experiment 2, mice underwent an 8-week moderate treadmill exercise paradigm followed by open field testing and tissue collection. Acute exercise decreased time spent in the centre of the open field in males only, suggesting increased anxiety-like behaviour in males. Acute exercise increased IL-6 and decreased TNF in serum, and increased amygdala principal component 1 (loading IL-12p70, IL-10, IFN-{gamma}, and TNF) in both sexes. Chronic exercise increased open field centre entries, increased IL-6 in the prefrontal cortex, decreased TNF in the dorsal hippocampus, and had minimal effects on circulating cytokines in both sexes. These results demonstrate that the effects of exercise on anxiety-related behaviour and cytokine levels depend on recurrence, tissue, and brain region. NEW & NOTEWORTHYOur work highlights the contrast between anxiogenic and anxiolytic effects of acute versus chronic exercise, respectively, in healthy mice. Acute and chronic exercise differentially affected circulating and brain cytokines, providing insight into physiological adaptations to exercise. Both sexes demonstrated similar cytokine responses to exercise. These similarities are novel with respect to exercise research and noteworthy given sex differences in anxiety with respect to acute exercise.

neuroscience↗

bioRxiv2026

Reproductive history differentially shapes the neural response of middle-aged females to estradiol therapy after a metabolic challenge

BackgroundAdvancing age, the APOE{square}4 allele, and female sex are the top nonmodifiable risk factors for Alzheimers disease (AD). Female-specific experiences, such as parity and hormone therapy (HT) affect aging biomarkers such as metabolism and immune signaling and may even affect AD risk. Estradiol (E2), a common component of many HTs, affects cognition and brain health in aging females although this may vary depending on parity, genotype, and metabolic status. We hypothesized that prior parity influences brain and metabolic health, including response to E2, depending on APOE genotype. MethodsMiddle-aged female (10 month) wildtype (WT) or humanized (h) APOE{square}4 expressing rats, with different reproductive experience (nulliparous or primiparous) were fed a Western (WD) or standard diet (SD) for 2 months. In the second month, rats were given E2 or vehicle (oil) injections daily. Fear associative learning, plasma metabolic hormones, hippocampal inflammatory signalling, and neuroplasticity (neurogenesis, synaptic protein) were assessed. ResultsFemales fed a WD gained weight and displayed metabolic dysregulation, regardless of genotype. E2 treatment reduced WD-induced weight gain and reduced metabolic hormones, with stronger effects in WT rats. E2 treatment increased dorsal hippocampal inflammatory signalling selectively in primiparous hAPOE{square}4 females fed a WD. Previous parity increased neurogenesis and reduced certain cytokines in the hippocampus of middle-aged WT rats under a SD. Both E2 treatment and previous parity decreased dorsal neurogenesis in hippocampus of hAPOE{square}4 rats. In hAPOE{square}4 females, higher weight was associated with reduced contextual fear memory, an effect driven by primiparous females. In the cued fear conditioning task, hAPOE{square}4 females displayed better cued fear memory than WT, however, WD exposure reduced cued fear memory in this group. Together, this indicates that diet and weight gain may be more detrimental to associative memory in hAPOE{square}4 females and that E2 treatment has more favourable outcomes in WT rats. ConclusionsPrevious parity alters how females respond to E2 and metabolic stress in midlife. Primiparous hAPOE{square}4 females were especially vulnerable to the effects of WD and E2, exhibiting more inflammation, impaired memory, and reduced weight-loss. These findings highlight the importance of considering parity and genotype when evaluating midlife metabolic and cognitive risk. HighlightsO_LIEstradiol (E2) treatment reduced body weight gain under a Western diet (WD), with the most pronounced effects in wildtype primiparous rats. C_LIO_LIWD increased several metabolic hormones, and E2 treatment reduced several metabolic hormones after a WD in middle age, only in WT rats C_LIO_LIIncreased body weight impaired contextual associative memory in primiparous hAPOE{square}4 females. C_LIO_LIE2 treatment increased dorsal hippocampal inflammatory signalling in primiparous hAPOE{square}4 rats and the WD increased inflammatory signalling in primiparous WT rats. C_LIO_LIPrevious parity, but not E2 treatment, increased neurogenesis in WT rats only under standard diet conditions whereas a WD decreased neurogenesis based on genotype and previous parity C_LI Plain English SummaryAlzheimers disease (AD) causes general cognitive decline, and females are at higher risk than males, particularly those carrying the APOE{varepsilon}4 gene. Female-specific experiences, such as previous pregnancy (parity) and hormone therapy, as well as lifestyle factors like body weight and diet, may further influence AD risk. We examined how estradiol (E2), a hormone involved in the menstrual cycle, pregnancy, and some hormone therapies can affect memory, brain inflammation, synaptic plasticity (brain cell connectivity), and growth of new neurons (neurogenesis) in middle-aged female rats. We compared females with or without the APOE{varepsilon}4 gene and with or without prior parity, fed either a high-fat, high-sugar Western diet (WD) or a standard diet (SD). WD increased body weight and worsened metabolic health, but the strength of negative effects depended on genotype and pregnancy history. In females with the APOE{varepsilon}4 gene and prior parity, higher body weight was linked to poorer memory. hAPOE{varepsilon}4 females on SD showed better memory than non-carriers but this benefit disappeared on WD, suggesting WD and obesity are particularly detrimental for hAPOE{square}4 carriers with prior parity. WD-fed primiparous hAPOE{square}4 females treated with E2 also showed higher brain inflammation than other groups. Pregnancy history and E2 treatment were associated with more favourable outcomes in females without the genetic risk for AD and fed a standard diet. These findings highlight the importance of a personalized approach to hormone therapy and brain health in aging females. hAPOE{square}4 females with prior parity were most sensitive to the effects of diet. Together, this suggests genetic background, reproductive history, and diet interact to affect memory, inflammation, and neurogenesis, as well as the effects of E2 on these factors.

neuroscience↗

bioRxiv2025

Morphological Identification of Ticks in district Swabi, Mardan, and Charsadda

Ticks are ectoparasitic arthropods that play a significant role in transmitting pathogens to humans and animals. This study aimed to address the research gap in understanding the morphological diversity and distribution of tick species in Swabi, Mardan, and Charsadda districts of Pakistan, where tick-borne diseases are prevalent but poorly documented. The primary objectives were to identify tick species, document their morphological characteristics, and map their distribution patterns across different habitats. Field surveys were conducted over nine months, collecting tick specimens from forests, grasslands, and residential areas. Specimens were preserved and analyzed using stereo-zoom microscopy and taxonomic keys for accurate classification. Key findings revealed a diverse tick fauna, including hard ticks (Ixodidae), with variations in body size, colour patterns, capitulum shape, and scutum features. Some species were widely distributed across all three districts, while others exhibited localized patterns. The study provides the first comprehensive morphological identification of tick species in these regions, highlighting their potential role in disease transmission. The implications of this research are significant for public health and disease control. The data can inform targeted interventions, enhance disease surveillance programs, and support the development of preventive measures to mitigate tick-borne diseases. By contributing to tick taxonomy and epidemiology, this study lays the groundwork for protecting public health in the study regions and beyond. This study addresses the lack of data on tick diversity in high-prevalence regions of Pakistan, providing critical insights for disease control and public health strategies. Limited information exists on the morphological diversity and distribution of tick species in Swabi, Mardan, and Charsadda districts. To identify tick species, document morphological characteristics, and map their distribution patterns in the study areas. Field surveys, specimen collection, stereo-zoom microscopy, and taxonomic classification were employed over nine months. Diverse tick fauna was identified, including hard ticks, with variations in morphology and distribution. Some species were widespread, while others were localized, highlighting potential disease transmission risks. The findings support targeted interventions, disease surveillance, and preventive measures, contributing to public health protection and tick-borne disease control in the region.

zoology↗

bioRxiv2025

IRG1/itaconate/NRF2/GSH axis in tumor-associated macrophages drives therapy resistance and immune evasion in BRCA1-deficient breast cancer

Tumor-associated macrophages (TAMs) are major contributors to immunosuppression and therapeutic resistance, including resistance to PARP inhibitors (PARPi) in BRCA1-deficient breast cancer. However, the mechanisms underlying TAM-mediated PARPi resistance remain unclear. Here, we demonstrate that TAM-derived glutathione (GSH) impairs the efficacy of PARPi by protecting tumor cells from DNA damage and ferroptosis while suppressing STING-mediated immune activation. Mechanistically, STAT5-driven upregulation of the IRG1/itaconate axis in TAMs rewires mitochondrial metabolism and activates NRF2-dependent GSH biosynthesis. GSH is subsequently released into the tumor microenvironment, where it is taken up by tumor cells, protecting them from PARPi-induced cytotoxicity and dampening immune responses. Pharmacological inhibition of IRG1 reverses these effects, restoring PARPi sensitivity and enhancing anti-tumor immunity in BRCA1-deficient tumor models. Collectively, these findings uncover a TAM-specific immunometabolic program that limits PARPi efficacy and highlight the IRG1/NRF2/GSH axis as a promising therapeutic target to improve treatment outcomes in BRCA1-associated breast cancer.

cancer biology↗

bioRxiv2025

Comparative virulence analysis of seven diverse strains of Orientia tsutsugamushi reveals a multifaceted and complex interplay of virulence factors responsible for disease.

Orientia tsutsugamushi is an obligate intracellular bacterium found in Leptotrombidium mites that causes the human disease scrub typhus. A distinguishing feature of O. tsutsugamushi is its extensive strain diversity, yet differences in virulence between strains are not well defined nor well understood. We sought to determine the bacterial drivers of pathogenicity by comparing murine infections using seven strains combined with epidemiological human data to rank each strain in terms of relative virulence. Murine cytokine expression data revealed that the two most virulent strains, Ikeda and Kato, induced higher levels of IL-6, IL-10, IFN-{gamma} and MCP-1 than other strains, consistent with increased levels of these cytokines in severe human scrub typhus patients. We sought to identify the mechanistic basis of the observed differential virulence between strains by comparing their genomes, in vitro growth properties and cytokine/chemokine induction in host cells. We found that there was no single gene or gene group that correlated with virulence, and no clear pattern of in vitro growth rate that predicted disease. However, microscopy-based analysis of the intracellular infection cycle revealed that the only fully avirulent strain in our study, TA686, differed from all the virulent strains in its subcellular localisation and expression of its surface protein ScaC. We conclude that drivers of pathogenicity in Orientia tsutsugamushi are distributed throughout the genome, likely in the large and varying arsenal of effector proteins encoded by different strains, and that these interact in complex ways to induce differing immune responses and thus differing disease outcomes in mammalian hosts. Author SummaryScrub typhus is a vector-borne human disease caused by the bacterium Orientia tsutsugmushi and spread by mites. There are numerous different strains of this bacterium with some causing more severe disease in humans than others, and some that do not cause any illness at all. The factors driving these differences are not yet understood, and gaining insight into them could aid in vaccine development and help predict the severity of disease caused by new isolates. To better determine the mechanistic basis of pathogenicity in scrub typhus, we carried out experiments in which we compared seven diverse strains for virulence in animals. We measured their ability to cause disease in mice, so that we could reliably classify them as virulent or avirulent in this model. We then analysed various genomic and biological aspects to identify disease markers in both mice and humans. We report here that there is no single factor that predicts whether a strain will be pathogenic or not, but that disease in scrub typhus is a complex process resulting from the activity of multiple bacterial genes working together to drive different immune responses in the host, resulting in either clearance of the bacteria from the host, or escalating disease. Future work exploring the relationship of bacterial effector proteins will help to disentangle this complex relationship in mechanistic detail.

microbiology↗

bioRxiv2024

Multi-organ immunity on a 3D-printed multi-tissue chip with tubing-free impeller pump

Multi-organ-on-chip systems (MOOCs) have the potential to mimic communication between organ systems and reveal mechanisms of health and disease. However, many existing MOOCs are challenging for non-experts to implement, due to complex tubing, electronics, or pump mechanisms. In addition, few MOOCs have incorporated immune organs such as the lymph node (LN), limiting their applicability to critical events such as vaccination. Here we developed a 3D-printed, user-friendly device and companion tubing-free impeller pump with the capacity to co-culture two or more tissue samples, including a LN, under a recirculating common media. Native tissue structure and immune function were incorporated by maintaining slices of murine LN tissue ex vivo in 3D-printed mesh supports for at least 24 hr. In a two-compartment model of a LN and an upstream injection site in mock tissue, vaccination of the multi-compartment chip was similar to in vivo vaccination in terms of locations of antigen accumulation and acute changes in activation markers and gene expression in the LN. We anticipate that in the future, this flexible platform will enable models of multi-organ immune responses throughout the body.

bioengineering↗

bioRxiv2023

ANGPTL8 R59W variant influences inflammation through modulating NF-κB pathway under TNFα stimulation

BackgroundANGPTL8 is known to regulate lipid metabolism and inflammation. It interacts with ANGPTL3 and ANGPTL4 to regulate LPL activity, and with IKK/{beta} to modulate NF-{kappa}B activity. Further, a SNP leading to ANGPTL8 R59W variant associates with reduced LDL/HDL and increased FBG in Hispanic and Arab individuals, respectively. In this study, we investigate the impact of R59W variant on the inflammatory activity of ANGPTL8. MethodsANGPTL8 R59W variant was genotyped in a discovery cohort of 867 Arab individuals from Kuwait. Plasma levels of ANGPTL8 and inflammatory markers were measured and tested for associations with the genotype; the associations were tested for replication in an independent cohort of 278 Arab individuals. Impact of the ANGPTL8 R59W variant on NF-{kappa}B activity was examined using approaches including overexpression, luciferase assay, and structural modeling of binding dynamics. ResultsThe ANGPTL8 R59W variant was associated with increased circulatory levels of TNF and IL7. NF-{kappa}B activity, as assessed by the increased in the phosphorylation of IKK-/{beta} protein, I{kappa}B, and NF-{kappa}B p-65 in R59W variant compared to wild type, and TNF stimulation further elevated it. This finding was substantiated by increased luciferase activity of NF-{kappa}B p65 with the R59W variant. Modeled structural and binding variation due to R59W change in ANGPTL8 agreed with the observed increase in NF-{kappa}B activity. ConclusionANGPTL8 R59W is associated with increased circulatory TNF, IL7 and NF-{kappa}B p65 activity. Weak transient binding of ANGPTL8 R59W variant explains its regulatory role on the NF-{kappa}B pathway and inflammation.

biochemistry↗

bioRxiv2023

Alternative splicing of the stress-sensitive regulator CIRBP sharpens the cellular response to bacterial infection

Cell autonomous responses to intracellular bacteria largely depend on gene expression reorganization. To gain isoform-level resolution into these regulations, we combined long- and short-read transcriptomic analyses of the response of intestinal epithelial cells to infection by the foodborne pathogen Listeria monocytogenes. Among the most striking isoform-based regulations, expression of the cellular stress response regulator CIRBP (cold-inducible RNA-binding protein) and of several SRSFs (serine/arginine-rich splicing factors) switched from canonical transcripts to nonsense-mediated decay-sensitive isoforms by inclusion of "poison exons". We showed that damage to host cell membranes caused by bacterial pore-forming toxins (listeriolysin O, perfringolysin, streptolysin, or aerolysin) led to the dephosphorylation of SRSF proteins via the inhibition of the kinase activity of CLK1, thereby driving CIRBP alternative splicing. CIRBP isoform usage was found to have consequences on infection, since selective repression of canonical CIRBP reduced intracellular bacterial load while that of the poison exon-containing isoform exacerbated it. Consistently, CIRBP-bound mRNAs were shifted towards stress-relevant transcripts in infected cells, with increased mRNA levels or reduced translation efficiency for some targets. Our results thus generalize the alternative splicing of CIRBP and SRSFs as a common response to biotic or abiotic stresses by extending its relevance to the context of bacterial infection.

molecular biology↗

bioRxiv2021

Innexin function dictates the spatial relationship between distal somatic cells in the Caenorhabditis elegans gonad without impacting the germline stem cell pool

Gap-junctional signaling mediates myriad cellular interactions in metazoans. Yet, how gap junctions control the positioning of cells in organs is not well understood. Innexins compose gap junctions in invertebrates and affect organ architecture. Here, we investigate the roles of gap-junctions in controlling distal somatic gonad architecture and its relationship to underlying germline stem cells in Caenorhabditis elegans. We show that a reduction of soma-germline gap-junctional activity causes displacement of distal sheath cells (Sh1) towards the distal end of the gonad. We confirm, by live imaging, transmission electron microscopy, and antibody staining, that bare regions--lacking somatic gonadal cell coverage of germ cells--are present between the distal tip cell (DTC) and Sh1, and we show that an innexin fusion protein used in a prior study encodes an antimorphic gap junction subunit that mispositions Sh1. We determine that, contrary to the model put forth in the prior study based on this fusion protein, Sh1 mispositioning does not markedly alter the position of the borders of the stem cell pool nor of the progenitor cell pool. Together, these results demonstrate that gap junctions can control the position of Sh1, but that Sh1 position is neither relevant for GLP-1/Notch signaling nor for the exit of germ cells from the stem cell pool.

developmental biology↗

bioRxiv2021

The CHK-2 antagonizing phosphatase PPM-1.D regulates meiotic entry via catalytic and non-catalytic activities

The transition from the stem cell/progenitor fate to meiosis is mediated by several redundant post-transcriptional regulatory pathways in C. elegans. Interfering with all three branches causes tumorous germlines. SCFPROM-1 comprises one branch and mediates a scheduled degradation step at entry into meiosis. prom-1 mutants show defects in timely initiation of events of meiotic prophase I, resulting in high rates of embryonic lethality. Here, we identify the phosphatase PPM-1.D/Wip1 as crucial substrate for PROM-1. We report that PPM-1.D antagonizes CHK-2 kinase, a key regulator for meiotic prophase initiation e.g., DNA double strand breaks, chromosome pairing and synaptonemal complex formation. We propose that PPM-1.D controls the amount of active CHK-2 by both catalytic and non-catalytic activities, where strikingly the non-catalytic regulation seems to be crucial at meiotic entry. PPM-1.D sequesters CHK-2 at the nuclear periphery and programmed SCFPROM-1 mediated degradation of PPM-1.D liberates the kinase and promotes meiotic entry.

cell biology↗

bioRxiv2021

A conserved paint box underlies color pattern diversity in Estrildid finches

Many animals exhibit typical color patterns that have been linked to key adaptive functions, yet the developmental mechanisms establishing these crucial designs remain unclear. Here, we surveyed color distribution in the plumage across a large number of passerine finches. Despite extreme apparent pattern diversity, we identified a small set of conserved color regions whose combinatory association can explain all observed patterns. We found these domains are instructed by early embryonic landmarks, and through profiling and comparative analyses produced a molecular map marking putative color domains in the developing skin. This revealed cryptic pre-patterning common to differently colored species, uncovering a simple molecular landscape underlying extensive color pattern variation.

developmental biology↗

bioRxiv2020

A comprehensive germline variant and expression analyses of ACE2, TMPRSS2 and SARS-CoV-2 activator FURIN genes from the Middle East: Combating SARS-CoV-2 with precision medicine

The severity of the new COVID-19 pandemic caused by the SARS-CoV-2 virus is strikingly variable in different global populations. SARS-CoV-2 uses ACE2 as a cell receptor, TMPRSS2 protease, and FURIN peptidase to invade human cells. Here, we investigated 1,378 whole-exome sequences of individuals from the Middle Eastern populations (Kuwait, Qatar, and Iran) to explore natural variations in the ACE2, TMPRSS2, and FURIN genes. We identified two activating variants (K26R and N720D) in the ACE2 gene that are more common in Europeans than in the Middle Eastern, East Asian, and African populations. We postulate that K26R can activate ACE2 and facilitate binding to S-protein RBD while N720D enhances TMPRSS2 cutting and, ultimately, viral entry. We also detected deleterious variants in FURIN that are frequent in the Middle Eastern but not in the European populations. This study highlights specific genetic variations in the ACE2 and FURIN genes that may explain SARS-CoV-2 clinical disparity. We showed structural evidence of the functionality of these activating variants that increase the SARS-CoV-2 aggressiveness. Finally, our data illustrate a significant correlation between ACE2 variants identified in people from Middle Eastern origins that can be further explored to explain the variation in COVID-19 infection and mortality rates globally.

genetics↗

bioRxiv2019

GLP-1 Notch - LAG-1 CSL control of the germline stem cell fate is mediated by transcriptional targets lst-1 and sygl-1

Stem cell systems are essential for the development and maintenance of polarized tissues. Intercellular signaling pathways control stem cell systems, where niche cells signal stem cells to maintain the stem cell fate/self renewal and inhibit differentiation. In the C. elegans germline, GLP-1 Notch signaling specifies the stem cell fate. We undertook a comprehensive genome-wide approach to identify transcriptional targets of GLP-1 signaling. We expected primary response target genes to be evident at the intersection of genes identified as directly bound by LAG-1, the C. elegans Notch pathway sequence-specific DNA binding protein, from ChIP-seq experiments, with genes identified as requiring GLP-1 signaling for RNA accumulation, from RNA-seq analysis. Furthermore, we performed a time-course transcriptomics analysis following auxin inducible degradation of LAG-1 to distinguish between genes whose RNA level was a primary or secondary response of GLP-1 signaling. Surprisingly, only lst-1 and sygl-1, the two known target genes of GLP-1 in the germline, fulfilled these criteria, indicating that these two genes are the primary response targets of GLP-1 Notch and may be the sole germline GLP-1 signaling protein-coding transcriptional targets for mediating the stem cell fate. In addition, three secondary response genes were identified based on their timing following loss of LAG-1, their lack of a LAG-1 ChIP-seq peak and that their glp-1 dependent mRNA accumulation could be explained by a requirement for lst-1 and sygl-1 activity. Moreover, our analysis also suggests that the function of the primary response genes lst-1 and sygl-1 can account for the glp-1 dependent peak protein accumulation of FBF-2, which promotes the stem cell fate and, in part, for the spatial restriction of elevated LAG-1 accumulation to the stem cell region. Author SummaryStem cell systems are central to tissue development, homeostasis and regeneration, where niche to stem cell signaling pathways promote the stem cell fate/self-renewal and inhibit differentiation. The evolutionarily conserved GLP-1 Notch signaling pathway in the C. elegans germline is an experimentally tractable system, allowing dissection of control of the stem cell fate and inhibition of meiotic development. However, as in many systems, the primary molecular targets of the signaling pathway in stem cells is incompletely known, as are secondary molecular targets, and this knowledge is essential for a deep understanding of stem cell systems. Here we focus on the identification of the primary transcriptional targets of the GLP-1 signaling pathway that promotes the stem cell fate, employing unbiased multilevel genomic approaches. We identify only lst-1 and sygl-1, two of a number of previously reported targets, as likely the sole primary mRNA transcriptional targets of GLP-1 signaling that promote the germline stem cell fate. We also identify secondary GLP-1 signaling RNA and protein targets, whose expression shows dependence on lst-1 and sygl-1, where the protein targets reinforce the importance of posttranscriptional regulation in control of the stem cell fate.

developmental biology↗

bioRxiv2019

Arabidopsis S2Lb links AtCOMPASS-like and SDG2 activity in histone H3 Lys-4 trimethylation independently from histone H2B monoubiquitination

The functional determinants of histone H3 Lys-4 trimethylation (H3K4me3), their potential dependency on histone H2B monoubiquitination (H2Bub) and their contribution to defining transcriptional regimes are poorly defined in plant systems. Unlike in S. cerevisiae, where a single SET1 protein catalyzes H3 Lys-4 trimethylation as part of COMPASS (COMPlex of proteins ASsociated with Set1), in Arabidopsis thaliana this activity involves multiple histone methyltransferases (HMTs). Among these, the plant-specific SDG2 (SET DOMAIN GROUP2) has a prominent role. We report that SDG2 co-regulates hundreds of genes with SWD2-like b (S2Lb), a plant ortholog of the Swd2 axillary subunit of yeast COMPASS. S2Lb co-purifies with the AtCOMPASS core subunit WDR5 from a high-molecular weight complex, and both S2Lb and SDG2 directly influence H3K4me3 enrichment over highly transcribed genes. S2Lb knockout triggers pleiotropic developmental phenotypes at the vegetative and reproductive stages, including reduced fertility and seed dormancy. Notwithstanding, s2lb seedlings display little transcriptomic defects as compared to the large repertoire of genes targeted by S2Lb, SDG2 or H3 Lys-4 trimethylation, suggesting that H3K4me3 enrichment is important for optimal gene induction during cellular transitions rather than for determining on/off transcriptional status. Moreover, unlike in budding yeast, most of the S2Lb and H3K4me3 genomic distribution does not rely on a trans-histone crosstalk with histone H2B monoubiquitination. Collectively, this study unveils that the evolutionarily conserved COMPASS-like complex has been coopted by the plant-specific SDG2 HMT and mediates H3K4me3 deposition through an H2Bub-independent pathway in Arabidopsis.

plant biology↗