RESUMO
Carotenoids are natural pigments that influence the color of citrus fruit. The red-colored carotenoid ß-citraurin is responsible for the peel color in "Newhall" orange (Citrus sinensis). Although jasmonates are known to regulate the biosynthesis and accumulation of carotenoids, their effects on ß-citraurin biosynthesis in citrus fruit remain unclear. Here, we determined that treatment with methyl jasmonate (MeJA) significantly promotes fruit coloration and ß-citraurin production in "Newhall" orange. A MeJA treatment induced the expression of CsMYC2, which encodes a transcription factor that serves as a master regulator of jasmonate responses. CsMYC2 bound the promoter of the gene that encodes carotenoid cleavage dioxygenase 4b (CsCCD4b), the key gene for ß-citraurin biosynthesis, and the promoters of genes that encode phytoene synthase (CsPSY), lycopene ß-cyclase (CsLCYb), and ß-carotene hydroxylase (CsBCH) and induced their expression. In addition, CsMYC2 promoted CsMPK6 expression. Notably, we found that CsMPK6 interacted with CsMYC2 and that this interaction decreased the stability and DNA-binding activity of CsMYC2. Thus, we conclude that negative feedback regulation attenuates JA signaling during the jasmonate-induced coloration of citrus fruit. Together, our findings indicate that jasmonates induce ß-citraurin biosynthesis in citrus by activating a CsMPK6-CsMYC2 cascade, thereby affecting fruit coloration.
Assuntos
Citrus sinensis , Citrus , Carotenoides/metabolismo , Citrus/genética , Citrus/metabolismo , Citrus sinensis/genética , Citrus sinensis/metabolismo , Frutas/genética , Frutas/metabolismo , Regulação da Expressão Gênica de Plantas , Geranil-Geranildifosfato Geranil-GeraniltransferaseRESUMO
Citrus is a model plant for studying adventitious embryos, a form of asexual reproduction controlled by a single dominant gene, RWP. This gene has been identified as the causal gene for nucellar embryogenesis, but its function has not yet been fully understood. In this study, we used the fast-growing Fortunella hindsii as a system to explore chromatin accessibility during the nucellar embryony initiation, emphasizing elevated chromatin accessibility in polyembryonic (PO) genotypes compared to monoembryonic ones (MO). Notably, a higher level of accessible chromatin was observed in one allele of the promoter region of FhRWP, consistent with increased expression of the allele carrying the causal structural variant. By independently performing RNAi and gene editing experiments on PO genotypes, we found the downregulation of FhRWP expression could reduce the number of nucellar embryos, while its knockout resulted in abnormal axillary bud development. In overexpression experiments, FhRWP was identified as having the unique capability of inducing the embryogenic callus formation in MO stem segments, possibly through the regulation of the WUS-CLV signaling network and the ABA and cytokinin pathway, marking the inaugural demonstration of FhRWP's potential to reignite somatic cells' embryogenic fate. This study reveals the pleiotropic function of RWP in citrus and constructs a regulatory network during adventitious embryo formation, providing a new tool for bioengineering applications in plant regeneration.
Assuntos
Citrus , Regulação da Expressão Gênica de Plantas , Fenótipo , Proteínas de Plantas , Citrus/genética , Citrus/fisiologia , Citrus/crescimento & desenvolvimento , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Plantas Geneticamente Modificadas , Sementes/genética , Sementes/crescimento & desenvolvimento , Edição de Genes , Genes de Plantas/genética , GenótipoRESUMO
Chromoplasts act as a metabolic sink for carotenoids, in which plastoglobules serve as versatile lipoprotein particles. PGs in chloroplasts have been characterized. However, the features of PGs from non-photosynthetic plastids are poorly understood. We found that the development of chromoplast plastoglobules (CPGs) in globular and crystalloid chromoplasts of citrus is associated with alterations in carotenoid storage. Using Nycodenz density gradient ultracentrifugation, an efficient protocol for isolating highly purified CPGs from sweet orange (Citrus sinensis) pulp was established. Forty-four proteins were defined as likely comprise the core proteome of CPGs using comparative proteomics analysis. Lipidome analysis of different chromoplast microcompartments revealed that the nonpolar microenvironment within CPGs was modified by 35 triacylglycerides, two sitosterol esters, and one stigmasterol ester. Manipulation of the CPG-localized gene CsELT1 (esterase/lipase/thioesterase) in citrus calli resulted in increased lipids and carotenoids, which is further evidence that the nonpolar microenvironment of CPGs contributes to carotenoid accumulation and storage in the chromoplasts. This multi-feature analysis of CPGs sheds new light on the role of chromoplasts in carotenoid metabolism, paving the way for manipulating carotenoid content in citrus fruit and other crops.
Assuntos
Citrus sinensis , Citrus , Citrus/genética , Citrus/metabolismo , Multiômica , Carotenoides/metabolismo , Plastídeos/metabolismo , Citrus sinensis/genética , Frutas/genética , Frutas/metabolismoRESUMO
As self-incompatibility is a major issue in pummelo breeding and production, its mechanism in citrus was analyzed to improve breeding efficiency and reduce production costs. Rutaceae belongs to S-RNase type of gametophytic self-incompatibility. While the function of S-RNase/SLF and the mechanism of self-incompatibility have been studied extensively, the transcriptional regulation of S-RNase has been less studied. We performed transcriptome sequencing with the styles of 'Shatian' pummelo on the day of anthesis and 1-5 days before anthesis, and found that the transcript level of S-RNase gradually decreased with flower development. By analyzing differentially expressed genes and correlation with the expression trend of S-RNase, we identified a candidate gene, CgHSFB1, and utilized biochemical experiments such as yeast one-hybrid assay, electrophoretic mobility shift assay and dual-luciferase assay, as well as transient transformation of citrus calli and Citrus microcarpa and demonstrated that CgHSFB1 could directly bind to the S1-RNase promoter and repress the expression of S1-RNase, which is involved in the pummelo self-incompatibility response. In contrast, CgHSFB1 did not bind to the promoter of S2-RNase, and there was specificity in the regulation of S-RNase.
Assuntos
Citrus , Flores , Regulação da Expressão Gênica de Plantas , Proteínas de Plantas , Ribonucleases , Autoincompatibilidade em Angiospermas , Citrus/genética , Citrus/fisiologia , Citrus/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Flores/genética , Flores/fisiologia , Flores/crescimento & desenvolvimento , Autoincompatibilidade em Angiospermas/genética , Ribonucleases/genética , Ribonucleases/metabolismo , Regiões Promotoras Genéticas/genética , Transcriptoma , Perfilação da Expressão GênicaRESUMO
Carotenoids contribute to fruit coloration and are valuable sources of provitamin A in the human diet. Abscisic acid (ABA) plays an essential role in fruit coloration during citrus fruit ripening, but little is known about the underlying mechanisms. Here, we identified a novel bZIP transcription activator called CsbZIP44, which serves as a central regulator of ABA-mediated citrus carotenoid biosynthesis. CsbZIP44 directly binds to the promoters of four carotenoid metabolism-related genes (CsDXR, CsGGPPs, CsBCH1 and CsNCED2) and activates their expression. Furthermore, our research indicates that CsHB5, a positive regulator of ABA and carotenoid-driven processes, activates the expression of CsbZIP44 by binding to its promoter. Additionally, CsHB5 interacts with CsbZIP44 to form a transcriptional regulatory module CsHB5-CsbZIP44, which is responsive to ABA induction and promotes carotenoid accumulation in citrus. Interestingly, we also discover a positive feedback regulation loop between the ABA signal and carotenoid biosynthesis mediated by the CsHB5-CsbZIP44 transcriptional regulatory module. Our findings show that CsHB5-CsbZIP44 precisely modulates ABA signal-mediated carotenoid metabolism, providing an effective strategy for quality improvement of citrus fruit and other crops.
Assuntos
Ácido Abscísico , Citrus , Humanos , Ácido Abscísico/metabolismo , Citrus/genética , Regulação da Expressão Gênica de Plantas/genética , Carotenoides/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Frutas/genética , Frutas/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismoRESUMO
Self-incompatibility (SI) is a crucial mechanism that prevents self-fertilization and inbreeding in flowering plants. Citrus exhibits SI regulated by a polymorphic S-locus containing an S-RNase gene and multiple S-locus F-box (SLF) genes. It has been documented that S-RNase functions as the pistil S determinant, but there is no direct evidence that the SLF genes closely linked with S-RNase function as pollen S determinants in Citrus. This study assembled the genomes of two pummelo (Citrus grandis) plants, obtained three novel complete and well-annotated S-haplotypes, and isolated 36 SLF or SLF-like alleles on the S-loci. Phylogenetic analysis of 138 SLFs revealed that the SLF genes were classified into 12 types, including six types with divergent or missing alleles. Furthermore, transformation experiments verified that the conserved S6-SLF7a protein can lead to the transition of SI to self-compatibility by recognizing non-self S8-RNase in 'Mini-Citrus' plants (S7S8 and S8S29, Fortunella hindsii), a model plant for citrus gene function studies. In vitro assays demonstrated interactions between SLFs of different S haplotypes and the Skp1-Cullin1-F-box subunit CgSSK1 protein. This study provides direct evidence that SLF controls the pollen function in Citrus, demonstrating its role in the 'non-self recognition' SI system.
Assuntos
Citrus , Proteínas F-Box , Filogenia , Proteínas de Plantas , Pólen , Ribonucleases , Autoincompatibilidade em Angiospermas , Citrus/genética , Citrus/fisiologia , Citrus/metabolismo , Autoincompatibilidade em Angiospermas/genética , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Pólen/genética , Pólen/fisiologia , Proteínas F-Box/genética , Proteínas F-Box/metabolismo , Ribonucleases/metabolismo , Ribonucleases/genética , Sequência de AminoácidosRESUMO
Arginine decarboxylase (ADC)-mediated putrescine (Put) biosynthesis plays an important role in plant abiotic stress response. SNF1-related protein kinases 2s (SnRK2s) and abscisic acid (ABA)-response element (ABRE)-binding factors (ABFs), are core components of the ABA signaling pathway involved in drought stress response. We previously reported that ADC of Poncirus trifoliata (PtrADC) functions in drought tolerance. However, whether and how SnRK2 and ABF regulate PtrADC to modulate putrescine accumulation under drought stress remains largely unclear. Herein, we employed a set of physiological, biochemical, and molecular approaches to reveal that a protein complex composed of PtrSnRK2.4 and PtrABF2 modulates putrescine biosynthesis and drought tolerance by directly regulating PtrADC. PtrABF2 was upregulated by dehydration in an ABA-dependent manner. PtrABF2 activated PtrADC expression by directly and specifically binding to the ABRE core sequence within its promoter and positively regulated drought tolerance via modulating putrescine accumulation. PtrSnRK2.4 interacts with and phosphorylates PtrABF2 at Ser93. PtrSnRK2.4-mediated PtrABF2 phosphorylation is essential for the transcriptional regulation of PtrADC. Besides, PtrSnRK2.4 was shown to play a positive role in drought tolerance by facilitating putrescine synthesis. Taken together, this study sheds new light on the regulatory module SnRK2.4-ABF2-ADC responsible for fine-tuning putrescine accumulation under drought stress, which advances our understanding on transcriptional regulation of putrescine synthesis.
Assuntos
Proteínas de Arabidopsis , Arabidopsis , Fosforilação , Putrescina/metabolismo , Arabidopsis/genética , Secas , Plantas Geneticamente Modificadas/metabolismo , Ácido Abscísico/metabolismo , Regulação da Expressão Gênica de Plantas , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Proteínas Serina-Treonina Quinases/genética , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas de Ligação a DNA/metabolismo , Fatores de Transcrição/metabolismoRESUMO
Drought and low temperature are two key environmental factors that induce adult citrus flowering. However, the underlying regulation mechanism is poorly understood. The bZIP transcription factor FD is a key component of the florigen activation complex (FAC) which is composed of FLOWERING LOCUS T (FT), FD, and 14-3-3 proteins. In this study, isolation and characterization of CiFD in citrus found that there was alternative splicing (AS) of CiFD, forming two different proteins (CiFDα and CiFDß). Further investigation found that their expression patterns were similar in different tissues of citrus, but the subcellular localization and transcriptional activity were different. Overexpression of the CiFD DNA sequence (CiFD-DNA), CiFDα, or CiFDß in tobacco and citrus showed early flowering, and CiFD-DNA transgenic plants were the earliest, followed by CiFDß and CiFDα. Interestingly, CiFDα and CiFDß were induced by low temperature and drought, respectively. Further analysis showed that CiFDα can form a FAC complex with CiFT, Ci14-3-3, and then bind to the citrus APETALA1 (CiAP1) promoter and promote its expression. However, CiFDß can directly bind to the CiAP1 promoter independently of CiFT and Ci14-3-3. These results showed that CiFDß can form a more direct and simplified pathway that is independent of the FAC complex to regulate drought-induced flowering through AS. In addition, a bHLH transcription factor (CibHLH96) binds to CiFD promoter and promotes the expression of CiFD under drought condition. Transgenic analysis found that CibHLH96 can promote flowering in transgenic tobacco. These results suggest that CiFD is involved in drought- and low-temperature-induced citrus flowering through different regulatory patterns.
Assuntos
Citrus , Citrus/genética , Fatores de Transcrição de Zíper de Leucina Básica/metabolismo , Proteínas de Plantas/metabolismo , Processamento Alternativo , Flores/fisiologia , Secas , Temperatura , Florígeno/metabolismo , Regulação da Expressão Gênica de Plantas , Plantas Geneticamente Modificadas/metabolismoRESUMO
Domesticated citrus varieties are woody perennials and interspecific hybrid crops of global economic and nutritional importance. The citrus fruit "hesperidium" is a unique morphological innovation not found in any other plant lineage. Efforts to improve the nutritional quality of the fruit are predicated on understanding the underlying regulatory mechanisms responsible for fruit development, including temporal control of chlorophyll degradation and carotenoid biosynthesis. Here, we investigated the molecular basis of the navel orange (Citrus sinensis) brown flavedo mutation, which conditions flavedo that is brown instead of orange. To overcome the limitations of using traditional genetic approaches in citrus and other woody perennials, we developed a strategy to elucidate the underlying genetic lesion. We used a multi-omics approach to collect data from several genetic sources and plant chimeras to successfully decipher this mutation. The multi-omics strategy applied here will be valuable in driving future gene discovery efforts in citrus as well as in other woody perennial plants. The comparison of transcriptomic and genomic data from multiple genotypes and plant sectors revealed an underlying lesion in the gene encoding STAY-GREEN (SGR) protein, which simultaneously regulates carotenoid biosynthesis and chlorophyll degradation. However, unlike SGR of other plant species, we found that the carotenoid and chlorophyll regulatory activities could be uncoupled in the case of certain SGR alleles in citrus and thus we propose a model for the molecular mechanism underlying the brown flavedo phenotype. The economic and nutritional value of citrus makes these findings of wide interest. The strategy implemented, and the results obtained, constitute an advance for agro-industry by driving opportunities for citrus crop improvement.
Assuntos
Carotenoides/metabolismo , Clorofila/metabolismo , Citrus sinensis/metabolismo , Frutas/metabolismoRESUMO
KEY MESSAGE: Pollen abortion could be mainly attributed to abnormal meiosis in the mutant. Multiomics analysis uncovered significant epigenetic variations between the mutant and its wild type during the pollen abortion process. Male sterility caused by aborted pollen can result in seedless fruit. A seedless Ponkan mandarin mutant (bud sport) was used to compare the transcriptome, methylome, and metabolome with its progenitor to understand the mechanism of citrus pollen abortion. Cytological observations showed that the anther of the mutant could form microspore mother cells, although the microspores failed to develop fertile pollen at the anther dehiscence stage. Based on pollen phenotypic analysis, pollen abortion could be mainly attributed to abnormal meiosis in the mutant. A transcriptome analysis uncovered the molecular mechanisms underlying pollen abortion between the mutant and its wild type. A total of 5421 differentially expressed genes were identified, and some of these genes were involved in the meiosis, hormone biosynthesis and signaling, carbohydrate, and flavonoid pathways. A total of 50,845 differentially methylated regions corresponding to 15,426 differentially methylated genes in the genic region were found between the mutant and its wild type by the methylome analysis. The expression level of these genes was negatively correlated with their methylation level, especially in the promoter regions. In addition, 197 differential metabolites were identified between the mutant and its wild type based on the metabolome analysis. The transcription and metabolome analysis further indicated that the expression of genes in the flavonoid, carbohydrate, and hormone metabolic pathways was significantly modulated in the pollen of the mutant. These results indicated that demethylation may alleviate the silencing of carbohydrate genes in the mutant, resulting in excessive starch and sugar hydrolysis and thereby causing pollen abortion in the mutant.
Assuntos
Citrus/metabolismo , Epigenoma , Metaboloma , Proteínas de Plantas/metabolismo , Pólen/metabolismo , Transcriptoma , Citrus/citologia , Citrus/genética , Citrus/crescimento & desenvolvimento , Metilação de DNA , Perfilação da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Genótipo , Meiose , Reguladores de Crescimento de Plantas/metabolismo , Infertilidade das Plantas/genética , Infertilidade das Plantas/fisiologia , Proteínas de Plantas/genética , Pólen/genética , Análise de SequênciaRESUMO
BACKGROUND: Previous reports have mainly focused on the volatiles in citrus fruits, and there have been few reports about the volatiles in citrus leaves and flowers. However, citrus leaves and flowers are also rich in volatile compounds with unique aromas. Here, to investigate the volatiles in citrus leaves and flowers, volatile profiling was performed on leaves from 62 germplasms and flowers from 25 germplasms. RESULTS: In total, 196 and 82 volatile compounds were identified from leaves of 62 citrus germplasms and flowers of 25 citrus germplasms, respectively. The dominant volatile terpenoids were more diverse in citrus leaves than in peels. A total of 34 volatile terpenoids were commonly detected in the leaves of at least 20 germplasms, among which 31 were overaccumulated in the leaves of wild or semiwild germplasms. This result was consistent with the high expression levels of five genes and one key gene of the mevalonate and 2-C-methyl-D-erythritol-4-phosphate (MEP) biosynthetic pathways, respectively, as well as the low expression levels of geranylgeranyl diphosphate synthase of the MEP pathway, relative to the levels in cultivars. Fully open flowers showed increased levels of four terpene alcohols and a decrease in sabinene content compared with balloon-stage flowers, especially in sweet orange. A monoterpene synthase gene was identified and functionally characterized as a sabinene synthase in vitro. CONCLUSIONS: Collectively, our results suggest that 31 important terpenoids are abundant in wild or semiwild citrus germplasms, possibly because of a negative effect of domestication on the volatiles in citrus leaves. The sweet smell of fully open flowers may be attributed to increased levels of four terpene alcohols. In addition, a sabinene synthase gene was identified by combined transcriptomic and metabolomic analyses.
Assuntos
Citrus/genética , Terpenos/metabolismo , Compostos Orgânicos Voláteis/metabolismo , Citrus/metabolismo , Flores/metabolismo , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Metabolômica , Odorantes , Folhas de Planta/metabolismo , Transcriptoma/genéticaRESUMO
Tetraploids have been reported to exhibit increased stress tolerance, but the underlying molecular and physiological mechanisms remain poorly understood. In this study, autotetraploid plants were identified by screening natural seedlings of trifoliate orange (Poncirus trifoliata). The tetraploids exhibited different morphology and displayed significantly enhanced drought and dehydration tolerance in comparison with the diploid progenitor. Transcriptome analysis indicated that a number of stress-responsive genes and pathways were differentially influenced and enriched in the tetraploids, in particular those coding for enzymes related to antioxidant process and sugar metabolism. Transcript levels and activities of antioxidant enzymes (peroxidase and superoxide dismutase) and sucrose-hydrolysing enzyme (vacuolar invertase) were increased in the tetraploids upon exposure to the drought, concomitant with greater levels of glucose but lower level of reactive oxygen species (ROS). These data indicate that the tetraploids might undergo extensive transcriptome reprogramming of genes involved in ROS scavenging and sugar metabolism, which contributes, synergistically or independently, to the enhanced stress tolerance of the tetraploid. Our results reveal that the tetraploids take priority over the diploid for stress tolerance by maintaining a more robust system of ROS detoxification and osmotic adjustment via elevating antioxidant capacity and sugar accumulation in comparison with the diploid counterpart.
Assuntos
Secas , Poncirus/fisiologia , Espécies Reativas de Oxigênio/metabolismo , Estresse Fisiológico , Açúcares/metabolismo , Tetraploidia , Regulação da Expressão Gênica de Plantas , Proteínas de Plantas , Plantas Geneticamente ModificadasRESUMO
Hongkong kumquat (Fortunella hindsii) is a wild citrus species characterized by dwarf plant height and early flowering. Here, we identified the monoembryonic F. hindsii (designated as 'Mini-Citrus') for the first time and constructed its selfing lines. This germplasm constitutes an ideal model for the genetic and functional genomics studies of citrus, which have been severely hindered by the long juvenility and inherent apomixes of citrus. F. hindsii showed a very short juvenile period (~8 months) and stable monoembryonic phenotype under cultivation. We report the first de novo assembled 373.6 Mb genome sequences (Contig-N50 2.2 Mb and Scaffold-N50 5.2 Mb) for F. hindsii. In total, 32 257 protein-coding genes were annotated, 96.9% of which had homologues in other eight Citrinae species. The phylogenomic analysis revealed a close relationship of F. hindsii with cultivated citrus varieties, especially with mandarin. Furthermore, the CRISPR/Cas9 system was demonstrated to be an efficient strategy to generate target mutagenesis on F. hindsii. The modifications of target genes in the CRISPR-modified F. hindsii were predominantly 1-bp insertions or small deletions. This genetic transformation system based on F. hindsii could shorten the whole process from explant to T1 mutant to about 15 months. Overall, due to its short juvenility, monoembryony, close genetic background to cultivated citrus and applicability of CRISPR, F. hindsii shows unprecedented potentials to be used as a model species for citrus research.
Assuntos
Sistemas CRISPR-Cas , Citrus/genética , Edição de Genes , Genoma de Planta , Plantas Geneticamente ModificadasRESUMO
Neohesperidosides are disaccharides that are present in some flavonoids and impart a bitter taste, which can significantly affect the commercial value of citrus fruits. In this study, we identified three flavonoid-7-O-di-glucosyltransferase (dGlcT) genes closely related to 1,2-rhamnosyltransferase (1,2RhaT) in citrus genomes. However, only 1,2RhaT was directly linked to the accumulation of neohesperidoside, as demonstrated by association analysis of 50 accessions and co-segregation analysis of an F1 population derived from Citrus reticulata × Poncirus trifoliata. In transgenic tobacco BY2 cells, over-expression of CitdGlcTs resulted in flavonoid-7-O-glucosides being catalysed into bitterless flavonoid-7-O-di-glucosides, whereas over-expression of Cit1,2RhaT converted the same substrate into bitter-tasting flavonoid-7-O-neohesperidoside. Unlike 1,2RhaT, during citrus fruit development the dGlcTs showed an opposite expression pattern to CHS and CHI, two genes encoding rate-limiting enzymes of flavonoid biosynthesis. An uncoupled availability of dGlcTs and substrates might result in trace accumulation of flavonoid-7-O-di-glucosides in the fruit of C. maxima (pummelo). Past human selection of the deletion and functional mutation of 1,2RhaT has led step-by-step to the evolution of the flavor-related metabolic network in citrus. Our research provides the basis for potentially improving the taste in citrus fruit through manipulation of the network by knocking-out 1,2RhaT or by enhancing the expression of dGlcT using genetic transformation.
Assuntos
Citrus/metabolismo , Flavonoides/metabolismo , Frutas/metabolismo , Poncirus/metabolismo , Citrus/enzimologia , Citrus/crescimento & desenvolvimento , Frutas/crescimento & desenvolvimento , Genes de Plantas , Hibridização Genética , Poncirus/enzimologia , Poncirus/crescimento & desenvolvimentoRESUMO
Nucellar embryony (NE) is an adventitious form of apomixis common in citrus, wherein asexual embryos initiate directly from nucellar cells surrounding the embryo sac. NE enables the fixation of desirable agronomic traits and the production of clonal offspring of virus-free rootstock, but impedes progress in hybrid breeding. In spite of the great importance of NE in citrus breeding and commercial production, little is understood about the underlying molecular mechanisms. In this study, the stages of nucellar embryo initiation (NEI) were determined for two polyembryonic citrus cultivars via histological observation. To explore the genes and regulatory pathways involved in NEI, we performed mRNA-seq and sRNA-seq analyses of ovules immediately prior to and at stages during NEI in the two pairs of cultivars. A total of 305 differentially expressed genes (DEGs) were identified between the poly- and monoembryonic ovules. Gene ontology (GO) analysis revealed that several processes are significantly enriched based on DEGs. In particular, response to stress, and especially response to oxidative stress, was over-represented in polyembryonic ovules. Nearly 150 miRNAs, comprising ~90 conserved and ~60 novel miRNAs, were identified in the ovules of either cultivar pair. Only two differentially expressed miRNAs (DEMs) were identified, of which the novel miRN23-5p was repressed whereas the targets accumulated in the polyembryonic ovules. This integrated study on the transcriptional and post-transcriptional regulatory profiles between poly- and monoembryonic citrus ovules provides new insights into the mechanism of NE, which should contribute to revealing the regulatory mechanisms of plant apomixis.
Assuntos
Apomixia/genética , Citrus/genética , MicroRNAs/genética , RNA Mensageiro/genética , Transcriptoma/genética , Citrus/crescimento & desenvolvimento , Regulação da Expressão Gênica no Desenvolvimento/genética , Regulação da Expressão Gênica no Desenvolvimento/fisiologia , Regulação da Expressão Gênica de Plantas/genética , Regulação da Expressão Gênica de Plantas/fisiologia , MicroRNAs/fisiologia , Óvulo Vegetal/genética , Óvulo Vegetal/fisiologia , Estresse Oxidativo , RNA Mensageiro/fisiologia , Reação em Cadeia da Polimerase em Tempo Real , Sementes/genética , Sementes/fisiologia , Análise de Sequência de RNARESUMO
In plants, the carotenoid cleavage dioxygenase 4 (CCD4) could target on plastoglobules and cleave specific carotenoids, producing apocarotenoids and volatile compounds. These compounds are important for color and aroma formation in fruits and flowers. In this study, five CCD4 gene members (CCD4a, b, c, d, and e) were investigated in different citrus species including mandarin, pummelo, and sweet orange. Sequence analysis showed that the CCD4 genes from all the species examined exhibited extensive allelic variability (including SNPs and frame-shift mutations). Furthermore, the distribution of the CCD4 allelic mutation sites supported our previous hypothesis that the sweet orange originated from the hybridization of mandarin and pummelo. A derived cleaved amplified polymorphic sequence (dCAPs) marker was then successfully developed based on the allelic polymorphism of CCD4c, providing an ideal molecular marker for studying the genetic relationship between citrus species. Quantitative RT-PCR analysis identified differential expression patterns for the CCD4 genes in tissues/organs, and CCD4b was shown to have a high-level expression in citrus fruit flavedos (especially those with a deep orange-reddish color). HPLC-based detection of a key component (i.e., ß-citraurin) for orange-reddish flavedo formation in different citrus revealed a positive correlation between CCD4b expression levels and the presence of ß-citraurin, suggesting that CCD4b may be responsible for ß-citraurin biosynthesis in flavedo. In summary, this study not only reinforced the anticipated roles of CCD4 genes in flavedo color formation in citrus, but also provided new information about gene expression patterns, allelic polymorphism characteristics, and sequence variability for this gene subfamily.
Assuntos
Carotenoides/metabolismo , Citrus/genética , Dioxigenases/genética , Proteínas de Plantas/genética , Sequência de Aminoácidos , Sequência de Bases , Citrus/classificação , Citrus/metabolismo , Dioxigenases/classificação , Dioxigenases/metabolismo , Mutação da Fase de Leitura , Frutas/genética , Frutas/metabolismo , Perfilação da Expressão Gênica , Regulação Enzimológica da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Variação Genética , Isoenzimas/classificação , Isoenzimas/genética , Isoenzimas/metabolismo , Dados de Sequência Molecular , Filogenia , Proteínas de Plantas/classificação , Proteínas de Plantas/metabolismo , Polimorfismo de Nucleotídeo Único , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Homologia de Sequência do Ácido Nucleico , Especificidade da Espécie , beta Caroteno/análogos & derivados , beta Caroteno/biossínteseRESUMO
The present study aims to analyse phylogenetic relationships, using internal transcribed spacer sequence data of ribosomal DNA (rDNA), across 24 Citrus species and close relatives by the evaluation of several parameters such as nucleotide substitution (r), nucleotide diversity (π) and the estimated values of transition/transversion bias (R). The observed results indicated the presence of a wide divergence pattern of rDNA in subfamily Aurantioideae. Maximum parsimony (MP) analysis inferred divergence pattern in the Citrus genus. We observed seven strongly supported clades among the subfamily Aurantioideae. We postulate that the present investigation provides a more robust topology of Citrus and its close relatives, which can significantly prove as an additional support to resolve the phylogenetic relationships in Citrus genera. Therefore, sequences of noncoding regions should exhibit more phylogenetically informative sites than the coding regions do, which is in accordance with the present study.
RESUMO
OBJECTIVE: To develop prognostic nomograms for overall survival (OS) and cancer-specific survival (CSS) probabilities in small cell lung cancer (SCLC) patients with brain metastasis (BM). METHODS: SCLC patients with BM from the Surveillance, Epidemiology, and End Results (SEER) database (2010-2015) were randomly allocated to training (n=1771) and validation (n=757) cohorts. Independent prognostic factors for OS and CSS were determined using univariate and multivariate Cox regression analyses in the training cohort, and prognostic nomograms for OS and CSS were constructed based on these factors. The efficacy of the nomograms was assessed using area under the receiver operating characteristic (ROC) curves (AUCs), calibration curves, decision curve analysis (DCA), net reclassification index (NRI), and integrated discrimination improvement (IDI), with the TNM staging model as a comparator. RESULTS: Multivariate Cox analysis identified age, sex, race, tumor size, N staging, and presence of liver/bone/lung metastases, chemotherapy, and radiotherapy as independent prognostic factors for both OS and CSS. Prognostic nomograms were developed based on these factors. In both the training and validation cohorts, the AUC values of the nomograms for OS and CSS were significantly above 0.7, surpassing those for TNM staging. Calibration curves demonstrated a high degree of concordance between predicted and actual survival. The constructed nomograms showed superior clinical utility compared to the TNM staging system, as evidenced by NRI, IDI, and DCA. CONCLUSIONS: This retrospective study successfully developed and validated prognostic nomograms for SCLC patients with BM, providing valuable tools for oncologists to enhance prognosis evaluation and guide clinical decision-making.
RESUMO
Several Millettia species are being investigated as medicinal ingredients due to their promising anti-cancer and anti-inflammatory properties. However, the application of Millettia species-derived compounds has been severely hindered by their poor aqueous solubility, rapid metabolism, and low bioavailability. Extracellular vesicles (EVs), which as membrane-bound phospholipid vesicle initiatively secreted through a variety of mammalian cells, are increasingly recognized as promising drug delivery vehicles. Therefore, EVs are with great potential to enhance both the stability and efficacy of the Millettia species-derived compounds in treatment. In this study, extracellular vesicles derived from chronic myelogenous leukemia cells are developed for delivering the extracts of Millettia speciosa Champ and Millettia pachyloba Drake-derived Homobutein. Notably, Homobutein-loaded EV (hEV) formed a stable and homogenous nanosized particle with high entrapment efficiency up to 55.7%. Moreover, EVs loaded with Homobutein were significantly more potent than free drugs in inhibiting K562 cell proliferation. The results demonstrated that intravenous injection of EV loaded with Homobutein effectively inhibits tumor growth in tumor-bearing mice compared to free Homobutein. Hence, this strategy can effectively enhance the efficacy of Millettia species-derived drugs in chronic myelogenous leukemia therapy.
RESUMO
OBJECTIVE: This study aimed to pinpoint independent predictors influencing overall survival (OS) and cancer-specific survival (CSS) in elderly patients with small cell lung cancer (SCLC) brain metastasis (BM), and to create and validate nomograms for OS and CSS prediction. METHODS: Data from elderly SCLC BM patients were extracted out of the Surveillance, Epidemiology, and End Results database, including 1200 patients identified from 2010 and 2015 who were randomly allocated into a training set and an internal validation set at a proportion of 7:3, and 666 patients diagnosed between 2018 and 2020 as a temporal external validation set. Independent predictors for OS and CSS were determined through univariate Cox analysis, least absolute shrinkage and selection operator analysis, and multivariate Cox analysis sequentially. Nomograms for OS and CSS were constructed, and validated by the internal and temporal external validation sets. RESULTS: Age, N stage, chemotherapy, and liver metastasis were determined as independent predictors of OS and CSS, while radiotherapy and surgery were not. Nomograms were constructed based on these independent predictors. The results of the receiver operator characteristic curves, the areas under the curve and calibration curve demonstrated that the nomograms exhibited commendable discriminative ability and calibration. Moreover, decision curve analysis, net reclassification improvement, and integrated discrimination improvement also suggested that the nomograms possessed superior clinical usefulness and predictive capability relative to the TNM system. CONCLUSIONS: Prognostic nomograms for elderly patients with SCLC BM have been developed, demonstrating good performance in terms of accuracy, reliability, and practicality.