CURLY LEAF Research Articles

SEP-like genes of Gossypium hirsutum promote flowering via targeting different loci in a concentration-dependent manner.

SEP genes are famous for their function in the morphological novelty of bisexual flowers. Although the diverse functions of SEP genes were reported, only the regulatory mechanisms underlying floral organ development have been addressed. In this study, we identified SEP-like genes in Gossypium and found that SEP3 genes were duplicated in diploid cotton varieties. GhSEP4.1 and GhSEP4.2 were abundantly transcribed in the shoot apical meristem (SAM), but only GhSEP4.2 was expressed in the leaf vasculature. The expression pattern of GhSEPs in floral organs was conserved with that of homologs in Arabidopsis, except for GhSEP2 that was preponderantly expressed in ovules and fibers. The overexpression and silencing of each single GhSEP gene suggested their distinct role in promoting flowering via direct binding to GhAP1 and GhLFY genomic regions. The curly leaf and floral defects in overexpression lines with a higher expression of GhSEP genes revealed the concentration-dependent target gene regulation of GhSEP proteins. Moreover, GhSEP proteins were able to dimerize and interact with flowering time regulators. Together, our results suggest the dominant role of GhSEP4.2 in leaves to promote flowering via GhAP1-A04, and differently accumulated GhSEP proteins in the SAM alternately participate in forming the dynamic tetramer complexes to target at the different loci of GhAP1 and GhLFY to maintain reproductive growth. The regulatory roles of cotton SEP genes reveal their conserved and diversified functions.

Mutation of histone H3 serine 28 to alanine influences H3K27me3-mediated gene silencing in Arabidopsis thaliana.

Histone modifications are essential for chromatin activity and play an important role in many biological processes. Trimethylation of histone H3K27 (H3K27me3) is a repressive modification established by Polycomb Repressive Complex 2 (PRC2). Although the presence of the histone H3 serine 28 phosphorylation (H3S28ph) modification at adjacent amino acid residues has both positive and negative effects on Polycomb silencing in mammals, little is known about the effect of H3S28ph on H3K27me3-mediated gene silencing in plants. In this study, we show that mutating H3S28A in Arabidopsis (Arabidopsis thaliana) causes a dominant-negative effect that leads to an early-flowering phenotype by promoting the expression of flowering-promoting genes independently of abnormal cell division. While H3S28ph levels decreased due to the H3S28A mutation, H3K27me3 levels at the same loci did not increase. Moreover, we observed decreased H3K27me3 levels at some known PRC2 target genes in H3.3S28A transgenic lines, rather than the expected enhanced H3K27me3-mediated silencing. In line with the reduced H3K27me3 levels, the expression of the PRC2 catalytic subunits CURLY LEAF and SWINGER decreased. Taken together, these data demonstrate that H3.3S28 is required for PRC2-dependent H3K27me3-mediated silencing in Arabidopsis, suggesting that H3S28 has a noncanonical function in H3K27me3-mediated gene silencing.

Evolutionary conservation of nested MIR159 structural microRNA genes and their promoter characterization in Arabidopsis thaliana.

MicroRNAs (miRNAs) are endogenous small RNAs, that are vital for gene expression regulation in eukaryotes. Whenever a pri-miRNA precursor includes another miRNA precursor, and both of these precursors may generate independent, non-overlapping mature miRNAs, we named them nested miRNAs. However, the extent of nested miR159 structural evolutionary conservation and its promoter characterization remains unknown. In this study, the sequence alignment and phylogenetic analysis reveal that the MIR159 family is ancient, and its nested miR159 structures are evolutionary conserved in different plant species. The overexpression of ath-MIR159a, including the 1.2 kb downstream region, has no effect on rescuing the mir159ab phenotype. The promoter truncation results revealed that the 1.0 kb promoter of ath-MIR159a is sufficient for rescuing the mir159ab phenotype. The cis-regulatory elements in the ath-miR159a promoters indicated functions related to different phytohormones, abiotic stresses, and transcriptional activation. While the MybSt1 motif-containing region is not responsible for activating the regulation of the miR159a promoter. The qRT-PCR results showed that overexpression of ath-MIR159a led to high expression levels of miR159a.1–5 and miR159a.1–3 and complemented the growth defect of mir159ab via downregulation of MYB33 and MYB65. Furthermore, continuously higher expression of the miR159a.2 duplex in transgenic lines with the curly leaf phenotype indicates that miR159a.2 is functional in Arabidopsis and suggests that it is possible for a miRNA precursor to encode several regulatory small RNAs in plants. Taken together, our study demonstrates that the nested miR159 structure is evolutionary conserved and miRNA-mediated gene regulation is more complex than previously thought.

HEXOKINASE1 forms a nuclear complex with the PRC2 subunits CURLY LEAF and SWINGER to regulate glucose signaling

The glucose sensor HEXOKINASE1 (HXK1) integrates myriad external and internal signals to regulate gene expression and development in Arabidopsis thaliana. However, how HXK1 mediates glucose signaling in the nucleus remains unclear. Here, using immunoprecipitation-coupled mass spectrometry, we show that two catalytic subunits of Polycomb Repressive Complex 2, SWINGER (SWN) and CURLY LEAF (CLF), directly interact with catalytically active HXK1 and its inactive forms (HXK1G104D and HXK1S177A ) via their evolutionarily conserved SANT domains. HXK1, CLF, and SWN target common glucose-responsive genes to regulate glucose signaling, as revealed by RNA sequencing. The glucose-insensitive phenotypes of the Arabidopsis swn-1 and clf-50 mutants were similar to that of hxk1, and genetic analysis revealed that CLF, SWN, and HXK1 function in the same genetic pathway. Intriguingly, HXK1 is required for CLF- and SWN-mediated histone H3 lysine 27 (H3K27me3) deposition and glucose-mediated gene repression. Moreover, CLF and SWN affect the recruitment of HXK1 to its target chromatin. These findings support a model in which HXK1 and epigenetic modifiers form a nuclear complex to cooperatively mediate glucose signaling, thereby affecting the histone modification and expression of glucose-regulated genes in plants.

Loss of Polycomb proteins CLF and LHP1 leads to excessive RNA degradation in Arabidopsis

Polycomb-group (PcG) proteins are major chromatin complexes that regulate gene expression, mainly described as repressors keeping genes in a transcriptionally silent state during development. Recent studies have nonetheless suggested that PcG proteins might have additional functions, including targeting active genes or acting independently of gene expression regulation. However, the reasons for the implication of PcG proteins and their associated chromatin marks on active genes are still largely unknown. Here, we report that combining mutations for CURLY LEAF (CLF) and LIKE HETEROCHROMATIN PROTEIN1 (LHP1), two Arabidopsis PcG proteins, results in deregulation of expression of active genes that are targeted by PcG proteins or enriched in associated chromatin marks. We show that this deregulation is associated with accumulation of small RNAs corresponding to massive degradation of active gene transcripts. We demonstrate that transcriptionally active genes and especially those targeted by PcG proteins are prone to RNA degradation, even though deregulation of RNA degradation following the loss of function of PcG proteins is not likely to be mediated by a PcG protein-mediated chromatin environment. Therefore, we conclude that PcG protein function is essential to maintain an accurate level of RNA degradation to ensure accurate gene expression.

Intronic long noncoding RNA, RICE FLOWERING ASSOCIATED (RIFLA), regulates OsMADS56-mediated flowering in rice

Long noncoding RNAs (lncRNAs) are known to play important roles in several plant processes such as flowering, organ development and stress response. However, studies exploring the diversity and complexity of lncRNAs and their mechanism of action in plants are far fewer that those in animals. Here, we show that an intronic lncRNA in rice (Oryza sativa L.), RICE FLOWERING ASSOCIATED (RIFLA), is required for the inhibition of OsMADS56 expression. RIFLA is produced from the first intron of the OsMADS56 gene. Overexpression of RIFLA in rice repressed OsMADS56 expression but activated the expression of flowering inducers Hd3a and RFT1. Additionally, RIFLA-overexpressing transgenic rice plants flowered earlier than the wild type. Under normal conditions, the transcript level of the rice enhancer of zeste gene OsiEZ1, a homolog of Arabidopsis histone H3K27-specific methyltransferase genes SWINGER (SWN) and CURLY LEAF (CLF), was as low as that of RIFLA, whereas the transcript level of OsMADS56 was relatively high. In the osiez1 mutant, OsMADS56 expression was upregulated, whereas RIFLA expression was downregulated. Additionally, RIFLA formed a complex with OsiEZ1. Together, these results suggest that the floral repressor activity of OsMADS56 is epigenetically regulated by RIFLA and OsiEZ1.

Epigenetic mechanisms affect the curled leaf phenotype in the hypomethylated ddc mutant of Arabidopsis thaliana

The ddc mutant of Arabidopsis thaliana is characterized by pleiotropic phenotypic alterations including a curl-shaped leaf, previously explained by disturbed auxin metabolism and transport. The present study was aimed at further explore the molecular bases underlying the abnormal phenotype of the ddc leaf. We demonstrated that genes specifically related to leaf fate commitment and morphogenesis were misexpressed on developing ddc leaves, such as upregulation of CURLY LEAF (CLF) and downregulation of ASYMMETRIC LEAVES2 (AS2), KNOTTED-like gene from A. thaliana (KNAT6), TEOSINTE-LIKE1 CYCLOIDEA and PROLIFERATING CELL FACTOR 2 (TCP2) and others. The CLF gene, encoding a component of Polycomb repressive complex 2 (PRC2) which adds trimethylation marks at Lys27 of histone H3, was overexpressed in the ddc mutant and concomitantly was correlated with DNA methylation-dependent repression of its negative regulator UCL1. KNAT6, encoding a class 1 KNOX homeotic gene, had increased H3K27me3 trimethylation levels, suggesting it is a target gene of the CLF containing PRC2 complex in the ddc mutant. We postulate that different epigenetic mechanisms modulate expression of genes related to auxin pathways as well as gene targets of Polycomb repressive action, during leaf morphogenesis.

BLISTER promotes seed maturation and fatty acid biosynthesis by interacting with WRINKLED1 to regulate chromatin dynamics in Arabidopsis.

WRINKLED1 (WRI1) is an important transcription factor that regulates seed oil biosynthesis. However, how WRI1 regulates gene expression during this process remains poorly understood. Here, we found that BLISTER (BLI) is expressed in maturing Arabidopsis thaliana seeds and acts as an interacting partner of WRI1. bli mutant seeds showed delayed maturation, a wrinkled seed phenotype, and reduced oil content, similar to the phenotypes of wri1. In contrast, BLI overexpression resulted in enlarged seeds and increased oil content. Gene expression and genetic analyses revealed that BLI plays a role in promoting the expression of WRI1 targets involved in fatty acid biosynthesis and regulates seed maturation together with WRI1. BLI is recruited by WRI1 to the AW boxes in the promoters of fatty acid biosynthesis genes. BLI shows a mutually exclusive interaction with the Polycomb-group protein CURLY LEAF (CLF) or the chromatin remodeling factor SWITCH/SUCROSE NONFERMENTING 3B (SWI3B), which facilitates gene expression by modifying nucleosomal occupancy and histone modifications. Together, these data suggest that BLI promotes the expression of fatty acid biosynthesis genes by interacting with WRI1 to regulate chromatin dynamics, leading to increased fatty acid production. These findings provide insights into the roles of the WRI1-BLI-CLF-SWI3B module in mediating seed maturation and gene expression.

Intensitas Penyakit pada Tanaman Ciplukan (Physalis angulata L.) yang Diberikan Kombinasi Perlakuan Pupuk Hayati (Mikoriza) dan Organik

Ciplukan plant is a plant that has potential to be used as a medicinal plant because it has various bioactive contents. Several studies that have been carried out are still limited to the potential, content and benefits of ciplukan plants. The aspect of disease attack on ciplukan plants, there has not been much research, even though this plant has various benefits and is currently being developed. This is what underlies this research. If previous research used organic and chemical fertilizers, it is also necessary to compare using biological fertilizers derived from mycorrhizal fungi against diseases found in ciplukan plants. The stages of the research carried out were planting preparation and application, observation, maintenance and data analysis. The aim of research was to determine the types and symptoms of disease, as well as important diseases-causing pathogens in ciplukan plants and the effect of a combination of biological (mycorrhizal) and organic fertilizers on diseases intensity. The results of the research obtained two types of diseases that occurred in ciplukan plants, namely leaf spot symptoms caused by Cercospora sp. and curly leaf symptoms caused by Cucumber Mosaic Virus (CMV). The combination of mycorrhizal treatment and organic fertilizer (manure) tends to increase the intensity of leaf spot disease and the incidence of curly leaf diseases.

Potential Biological Activities of Peptides Generated during Casein Proteolysis by Curly Kale (Brassica oleracea L. var. sabellica L.) Leaf Extract: An In Silico Preliminary Study.

This study is a brief report on the proteolytic activity of curly kale leaf extract against casein. Casein degradation products and an in silico analysis of the biological activity of the peptides obtained was performed. The efficiency of casein hydrolysis by curly kale extract was determined using SDS–PAGE and by peptide concentration determination. The pattern of the enzymatic activity was determined by MALDI–TOF MS analysis. The results showed that α- and β-casein were more resistant to curly kale extract hydrolysis, whereas κ-casein was absent in the protein profile after 8 h of proteolysis, and all casein fractions were completely hydrolyzed after 24 h of incubation. Based on sequence analysis, seven peptides were identified, with molecular mass in the range of 1151–3024 Da. All the peptides were products of β-casein hydrolysis. The identified amino acid sequences were analyzed in BIOPEP, MBPDB, and FeptideDB databases in order to detect the potential activities of the peptides. In silico analysis suggests that the β-casein-derived peptides possess sequences of peptides with ACE inhibitory, antioxidant, dipeptidyl peptidase IV inhibitory, antithrombotic, immunomodulatory, and antiamnesic bioactivity. Our study was first to evaluate the possibility of applying curly kale leaf extract to generate biopeptides through β-casein hydrolysis.

Arabidopsis CURLY LEAF functions in leaf immunity against fungal pathogens by concomitantly repressing SEPALLATA3 and activating ORA59.

Arabidopsis non-host resistance against non-adapted fungal pathogens including Colletotrichum fungi consists of pre-invasive and post-invasive immune responses. Here we report that non-host resistance against non-adapted Colletotrichum spp. in Arabidopsis leaves requires CURLY LEAF (CLF), which is critical for leaf development, flowering and growth. Microscopic analysis of pathogen behavior revealed a requirement for CLF in both pre- and post-invasive non-host resistance. The loss of a functional SEPALLATA3 (SEP3) gene, ectopically expressed in clf mutant leaves, suppressed not only the defect of the clf plants in growth and leaf development but also a defect in non-host resistance against the non-adapted Colletotrichum tropicale. However, the ectopic overexpression of SEP3 in Arabidopsis wild-type leaves did not disrupt the non-host resistance. The expression of multiple plant defensin (PDF) genes that are involved in non-host resistance against C. tropicale was repressed in clf leaves. Moreover, the Octadecanoid-responsive Arabidopsis 59 (ORA59) gene, which is required for PDF expression, was also repressed in clf leaves. Notably, when SEP3 was overexpressed in the ora59 mutant background, C. tropicale produced clear lesions in the inoculated leaves, indicating an impairment in non-host resistance. Furthermore, ora59 plants overexpressing SEP3 exhibited a defect in leaf immunity to the adapted Colletotrichum higginsianum. Since the ora59 plants overexpressing SEP3 did not display obvious leaf curling or reduced growth, in contrast to the clf mutants, these results strongly suggest that concomitant SEP3 repression and ORA59 induction via CLF are required for Arabidopsis leaf immunity to Colletotrichum fungi, uncoupled from CLF's function in growth and leaf development.

Influence of Curly Leaf Trait on Cottonseed Micro-Nutrient Status in Cotton (Gossypium hirsutum L.) Lines.

Cottonseed is a source of nutrients, including protein, oil, and macro- and micro-nutrients. Micro-nutrients such as boron (B), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn) are essential for plant and human health. Deficiencies of these micro-nutrients in soil lead to poor crop production and poor seed quality. Micro-nutrient deficiencies in the human diet lead to malnutrition and serious health issues. Therefore, identifying new cotton lines containing high nutritional qualities such as micro-nutrients, and understanding plant traits influencing micro-nutrients are essential. The objective of this research was to investigate the effects of leaf shape (curly leaf: CRL) on cottonseed B, Cu, Fe, Mn, Ni (nickel), and Zn in two near-isogenic cotton lines differing in leaf shape (DP 5690 wild-type with normal leaves and DP 5690 CRL). We also used Uzbek CRL, the source of the curly leaf trait, for comparison. A field experiment was conducted in 2014 and 2015 in Stoneville, MS, USA. The experiment was a randomized complete block design with three replicates. The results showed that, in 2014, both DP 5690 wild-type and Uzbek CRL had higher seed B, Cu, Fe, and Ni than in DP 5690 CRL. The accumulation of Mn and Zn in seeds of DP 5690 CRL was higher than in DP 5690 wild-type and Uzbek CRL. However, in 2015, the concentrations of B, Cu, Fe, and Ni, including Mn and Zn, were higher in both DP 5690 wild-type and Uzbek CRL than in DP 5690 CRL. Positive and negative correlations existed in 2014; however, only positive correlations existed between all nutrients in 2015. This research demonstrated that leaf shape can alter cottonseed micro-nutrients status. As Uzbek CRL behaved similar to wild-type, both leaf shape and other factors contributed to the alteration in seed micronutrients, affecting seed nutritional qualities. Therefore, leaf-shape partially contributed to the changes in micro-nutrients in cottonseed. The negative and positive correlations in 2014, and only positive correlations in 2015, were likely due to the heat difference between 2014 and 2015 as 2015 was warmer than 2014. Significant levels of seed micro-nutrients were shown between these lines, providing opportunities for breeders to select for high seed micro-nutrients in cotton. Additionally, the current research provides researchers with physiological information on the impact of leaf shape on seed nutritional quality. The leaf shape trait can also be used as a tool to study leaf development, physiological, biochemical, and morphological processes.

A single amino acid residue substitution in BraA04g017190.3C, a histone methyltransferase, results in premature bolting in Chinese cabbage (Brassica rapa L. ssp. Pekinensis)

BackgroundFlowering is an important inflection point in the transformation from vegetative to reproductive growth, and premature bolting severely decreases crop yield and quality.ResultsIn this study, a stable early-bolting mutant, ebm3, was identified in an ethyl methanesulfonate (EMS)-mutagenized population of a Chinese cabbage doubled haploid (DH) line ‘FT’. Compared with ‘FT’, ebm3 showed early bolting under natural cultivation in autumn, and curled leaves. Genetic analysis showed that the early-bolting phenotype was controlled by a single recessive nuclear gene. Modified MutMap sequencing, genotyping analyses and allelism test provide strong evidence that BrEBM3 (BraA04g017190.3 C), encoding the histone methyltransferase CURLY LEAF (CLF), was the strongly candidate gene of the emb3. A C to T base substitution in the 14th exon of BrEBM3 resulted in an amino acid change (S to F) and the early-bolting phenotype of emb3. The mutation occurred in the SET domain (Suppressor of protein-effect variegation 3–9, Enhancer-of-zeste, Trithorax), which catalyzes site- and state-specific lysine methylation in histones. Tissue-specific expression analysis showed that BrEBM3 was highly expressed in the flower and bud. Promoter activity assay confirmed that BrEBM3 promoter was active in inflorescences. Subcellular localization analysis revealed that BrEBM3 localized in the nucleus. Transcriptomic studies supported that BrEBM3 mutation might repress H3K27me3 deposition and activate expression of the AGAMOUS (AG) and AGAMOUS-like (AGL) loci, resulting in early flowering.ConclusionsOur study revealed that an EMS-induced early-bolting mutant ebm3 in Chinese cabbage was caused by a nonsynonymous mutation in BraA04g017190.3 C, encoding the histone methyltransferase CLF. These results improve our knowledge of the genetic and genomic resources of bolting and flowering, and may be beneficial to the genetic improvement of Chinese cabbage.

Effect of Some Organic Materials on Yield and Plant Nutrient Content of Curly Leaf Salad (Lactuca sativa var. Crispa)

Caipira (Lactuca sativa var. Crispa) kıvırcık yaprak salata çeşidinin kullanıldığı çalışma, 3 farklı organik materyal (vermikompost, gidya, leonardit) ve bunların farklı dozları (% 3, % 6, % 9) ile bahçe toprağı kullanılan kontrol grubu (% 0) olarak tasarlanmıştır. Bu çalışmada, insan beslenmesinde önemli yer tutan ve kimyasal azotlu gübreler uygulandığında, yapraklarında nitrat/nitrit birikimi riski taşıyan salatalarda organik materyal olarak farklı dozlarda vermikompost, gidya ve leonardit uygulamalarının bitki besin elementi içeriğine etkilerinin belirlenmesi amaçlanmıştır. Araştırma bulgularına göre uygulanan organik maddelerin bakılan verim komponentleri üzerine etkileri önemli bulunmuştur. Vermikompost uygulamasının verimi yaklaşık 2 kat artırdığı halde dozlar arasında istatistiksel olarak farklılık bulunmamıştır. Ayrıca vermikompostun kıvırcık yaprak salatada erkenciliğe etkisinin istatistiksel olarak önemli olduğu ve özellikle K+, Zn+ ve Cu+ elementlerinin bitki bünyesine alımına vermikompostun iyi sonuçlar verdiği belirlenmiştir. Genel olarak bitki besin elementi içeriği bakımından gidya uygulamalarının olumlu sonuçlar vermediği belirlenmiştir.

The effect of application of compost and frass from Black Soldier Fly Larvae (Hermetia illucens L.) on growth of Pakchoi (Brassica rapa L.)

Pot experiment was conducted to observe the effect of frass (insect feces) from Black Soldier Fly larvae (BSFL) as soil amendments at different application rates in comparation with other organic fertilizers on Pakchoi (Brassica rapa L). The experimental design was completely random with seven treatments, namely compost, compost+LOB (liquid organic biofertilizer), 5%, 10%, and 15% BSF frass, chemical fertilizer (NPK, equivalent to 10 kg/ha), and soil as a control. After 35 days planting, the result showed that Pakchoi cultivated with compost+LOB, compost, and BSF frass produced the highest biomass compared to control and NPK treatment significantly. The highest total plant weight was achieved in the treatment of Compost+LOB (24.4 gr), followed by 10% BSF frass (23.3 gr), compost (21.8 gr), 15% BSF frass (20.7 gr), 5% BSF frass (19,8 gr), NPK (1.3 gr ) and control soil (0.9 gr). While the chlorophyll content was not significantly different between all treatments, the application of BSF frass tended to be higher but with curly leaf symptoms than other treatments. The population of P solubilizing bacteria and the activity of PME-ase enzyme in soil were also higher in the treatment of compost, compost+LOB, and BSF frass compared to control and NPK treatment.

Cottonseed Protein, Oil, and Minerals in Cotton (Gossypium hirsutum L.) Lines Differing in Curly Leaf Morphology.

Cottonseed is an important source of protein, oil, and minerals for human health and livestock feed. Therefore, understanding the physiological and genetic traits influencing the nutrient content is critical. To our knowledge, there is no information available on the effects of leaf shape—curly leaf (CRL)—on cottonseed protein, oil, and minerals. Therefore, the objective of the current research was to investigate the effect of the curly leaf trait on cottonseed protein, oil, and minerals in cotton lines differing in leaf shape. Our hypothesis was that since leaf shape is known to be associated with nutrient uptake, assimilation, and photosynthesis process, leaf shape can influence seed protein, oil, and minerals. A two-year field experiment using two curly leaf lines (Uzbek CRL and DP 5690 CRL) and one normal leaf (DP 5690 wild type) line was conducted in 2014 and 2015 in Stoneville, MS, USA. The experiment was a randomized complete block design with three replicates. The results showed that both Uzbek CRL and DP 5690 wild type lines had higher seed oil, and nutrients N, P, K, and Mg than DP 5690 CRL. Calcium was higher in DP 5690 CRL for two years and protein was only higher than the parents in 2015. Consistent significant positive and negative correlations between some nutrients were observed, which may be due to environmental conditions, especially heat. This indicates that curly leaf trait may partially regulate the accumulation of these nutrients in seeds. The results demonstrated that leaf shape trait—curly leaf—can affect cottonseed nutritional qualities. This research is important to breeders for cotton selection for high seed oil or protein, and to other researchers to further understand the genetic impact of leaf shapes on seed nutritional quality. It is also important for scientists to use leaf shape as a tool for physiological, biochemical, and morphological research related to leaf development.

Respuesta del perejil crespo a diferentes densidades de población de Meloidogyne arenaria

The effect of initial population density (Pi) of the peanut root-knot nematode, Melodoigyne arenaria, on curly leaf parsley growth was assessed in this study. The population densities of M. arenaria ranged from 0 to 64 eggs + second-stage juveniles (J2)/cm3 soil in sterile sandbags. The root gall index (RGI), reproduction factor (RF), fresh leaf weight (FLW), dry leaf weight (DLW), root fresh weight (RFW), root length (RL), leaf height (LH), and chlorophyll index (SPAD) were determined at 90 days after inoculation. FLW, DLW, RFW, LH, and SPAD data were fitted to the Seinhorst equation, y = m + (1 - m) zPi-T, to determine the tolerance limit T = 0.25 eggs +J2/cm3 soil for FLW, DLW, RFW, and LH, with relative means (m) of 0.52, 0.24, 0.22, and 0.4 respectively; conversely, the T value for SPAD was 0.125 eggs + J2/cm3 soil and with a m of 0.26. All biometric variables decreased with an increase in the initial population density (Pi). Nevertheless, the highest RF of M. arenaria in parsley was 78.92 for a Pi = 8 eggs + J2/cm3 soil, with an RGI value of 5 from Pi = 1 eggs + J2/cm3. Curly leaf parsley growth decreased with an increase in Pi of M. arenaria.

Polycomb mutant partially suppresses DNA hypomethylation-associated phenotypes in Arabidopsis.

In plants and mammals, DNA methylation and histone H3 lysine 27 trimethylation (H3K27me3), which is deposited by the polycomb repressive complex 2, are considered as two specialized systems for the epigenetic silencing of transposable element (TE) and genes, respectively. Nevertheless, many TE sequences acquire H3K27me3 when DNA methylation is lost. Here, we show in Arabidopsis thaliana that the gain of H3K27me3 observed at hundreds of TEs in the ddm1 mutant defective in the maintenance of DNA methylation, essentially depends on CURLY LEAF (CLF), one of two partially redundant H3K27 methyltransferases active in vegetative tissues. Surprisingly, the complete loss of H3K27me3 in ddm1 clf double mutant plants was not associated with further reactivation of TE expression nor with a burst of transposition. Instead, ddm1 clf plants exhibited less activated TEs, and a chromatin recompaction as well as hypermethylation of linker DNA compared with ddm1 Thus, a mutation in polycomb repressive complex 2 does not aggravate the molecular phenotypes linked to ddm1 but instead partially suppresses them, challenging our assumptions of the relationship between two conserved epigenetic silencing pathways.

The transcriptional repressors VAL1 and VAL2 recruit PRC2 for genome-wide Polycomb silencing in Arabidopsis

The Polycomb repressive complex 2 (PRC2) catalyzes histone H3 Lys27 trimethylation (H3K27me3) to repress gene transcription in multicellular eukaryotes. Despite its importance in gene silencing and cellular differentiation, how PRC2 is recruited to target loci is still not fully understood. Here, we report genome-wide evidence for the recruitment of PRC2 by the transcriptional repressors VIVIPAROUS1/ABI3-LIKE1 (VAL1) and VAL2 in Arabidopsis thaliana. We show that the val1 val2 double mutant possesses somatic embryonic phenotypes and a transcriptome strikingly similar to those of the swn clf double mutant, which lacks the PRC2 catalytic subunits SWINGER (SWN) and CURLY LEAF (CLF). We further show that VAL1 and VAL2 physically interact with SWN and CLF in vivo. Genome-wide binding profiling demonstrated that they colocalize with SWN and CLF at PRC2 target loci. Loss of VAL1/2 significantly reduces SWN and CLF enrichment at PRC2 target loci and leads to a genome-wide redistribution of H3K27me3 that strongly affects transcription. Finally, we provide evidence that the VAL1/VAL2–RY regulatory system is largely independent of previously identified modules for Polycomb silencing in plants. Together, our work demonstrates an extensive genome-wide interaction between VAL1/2 and PRC2 and provides mechanistic insights into the establishment of Polycomb silencing in plants.

The complexity of PRC2 catalysts CLF and SWN in plants.

Polycomb repressive complex 2 (PRC2) is an evolutionally conserved multisubunit complex essential for the development of eukaryotes. In Arabidopsis thaliana (Arabidopsis), CURLY LEAF (CLF) and SWINGER (SWN) are PRC2 catalytic subunits that repress gene expression through trimethylating histone H3 at lysine 27 (H3K27me3). CLF and SWN function to safeguard the appropriate expression of key developmental regulators throughout the plant life cycle. Recent researches have advanced our knowledge of the biological roles and the regulation of the activity of CLF and SWN. In this review, we summarize these recent findings and highlight the redundant and differential roles of CLF and SWN in plant development. Further, we discuss the molecular mechanisms underlying CLF and SWN recruitment to specific genomic loci, as well as their interplays with Trithorax-group (TrxG) proteins in plants.