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Comparative genomics and phylogenetic analysis of three Malvaceae species on the basis of chloroplast genomes.

INTRODUCTION: The Malvaceae family shows rich species diversity and has substantial economic and medicinal value. However, the frequent interspecific hybridization among members of this family has resulted in confused phylogenetic relationships among the groups, limiting the usefulness of traditional classification methods. METHODS: This study aimed to investigate the phylogenetic relationships among selected taxa of Malvaceae by evaluating 23 chloroplast (CP) genomes, including three newly assembled CP genomes. Among these three genomes, the CP genome of Hibiscus schizopetalus L. was reported for the first time, while the CP genomes of Alcea rosea L. and Hibiscus grewiifolius L., which have been deposited in NCBI, were re-analyzed here alongside newly generated data for comparative purposes. In addition, 20 downloaded CP genomes encompassing 13 genera were analyzed using SNPs in whole CP genomes data. RESULTS: The results showed that the genomes ranged from 160,403 to 161,978 base pairs in length and consisted of small single copies (SSCs) and large single copies (LSCs) separated by two inverted repeat sequences (IRs), forming a typical quadripartite circular structure. The entire genome sequence showed relative conservation across species in terms of structure, GC content, codon usage, and gene composition. The mutation sites were mainly located in the LSC and SSC regions, and the variability in the non-coding regions was higher than that in the coding regions. The nucleotide polymorphism (Pi) analysis identified the non-coding regions such as ndhF-rpl32 and psbZ-trnG as high variable hotspots. A maximum likelihood phylogenetic tree was constructed based on SNPs in whole CP genomes data. The phylogenetic analysis divided these 23 species into five highly supported clades. It also revealed a close sister-group relationship between Abelmoschus and Hibiscus species, suggesting that Hibiscus may have a separate lineage from okra species. DISCUSSION: In conclusion, the increasing availability of CP genome resources will enhance our understanding of the classification and evolutionary patterns of the Malvaceae family. The development of molecular markers will provide important molecular evidence for precise identification and classification revision of plants in this family.

Malvaceae

Unraveling evolutionary relationships in the Sida generic alliance (Malvaceae, Malvoideae): a phylogenetic and cytotaxonomic overview.

Sida (Malvaceae), the largest Malveae-Abutilinae member, has poorly defined morphological limits which overlaps with 11 phylogenetically closely related genera that comprises the "Sida generic alliance". The 12 genera are distributed in the tropics especially in Brazil where one third of its species diversity is found. Evolutionary relationships within Sida generic alliance remain unresolved due to morphological convergence, limited taxon sampling, and lack of integrative approaches including cytogenetic data. We reconstructed the phylogeny of Sida and allied genera using a multilocus dataset (nuclear ITS and seven plastid loci) including 193 species classified in 19 genera and analyzed chromosome evolution using cytogenetic data (chromosome number) for 79 species of the 19 genera. The phylogeny recovered seven clades-Abutilon, Bakeridesia, Callianthe, Gaya, and three Sida clades (I-III)-and confirmed the polyphyly of Sida, the largest genera. We detected reticulate evolution, with incongruence between nuclear and plastid topologies. Chromosome number ranged from 2n = 12 to 60 and represented synapomorphies for most clades. Ancestral character reconstruction indicated that ascending dysploidy and polyploidy predominated in karyotype evolution of Sida and allied genera. Our results reveal taxonomic incongruence in current classifications probably related to reticulate evolution. A generic-level taxonomic revision is necessary and should rely on integrated phylogenetic and karyotypic evidence. This study provides a framework for phylogenetic systematics and emphasizes the role of Brazil as a hotspot for plant genomic research.

Phylogeny

Evolutionary dynamics of the chloroplast genome in Abutilon (Malvoideae, Malvaceae).

The genus Abutilon Mill. (Malvaceae) comprises approximately 178 species distributed across tropical and subtropical regions, many of which hold significant ornamental, economic, and medicinal value; yet its taxonomic classification remains challenging. In this study, six species were sequenced from herbarium specimens, and the chloroplast (cp.) genomes of ten additional species were assembled de novo from publicly available raw data. Three previously reported cp. genomes were also incorporated to characterise cp. genome structure, identify polymorphic loci, and perform phylogenetic analyses. The cp. genomes ranged from 159,458 to 160,454 bp and exhibited the typical quadripartite structure, with each genome containing 112 unique genes (78 protein-coding, 30 tRNA, and 4 rRNA) that showed conserved content and organisation. These genomes exhibited high similarity in GC content, inverted repeat boundaries, relative synonymous codon usage, amino acid frequencies, and substitution patterns. However, notable variation was observed in the total number of simple sequence repeats, ranging from 70 to 97 per genome. Selection analyses indicated predominant purifying selection, with evidence of episodic positive selection detected in rpoC2, rbcL, and ycf1. Two codons in rbcL were clade-specific and provided phylogenetic signal distinguishing Australian and Old World pantropical species. Nucleotide diversity analysis identified six highly polymorphic intergenic spacers (trnH-psbA, rps19-rpl2, psbT-pbf1, psaC-ndhD, trnR-atpA, and ndhJ-ndhK) that may be suitable for taxonomic studies. The phylogeny from maximum likelihood (ML) and Bayesian inference (BI) resolved two major clades: one comprising an exclusively Australian lineage occurring predominantly in arid and semi-arid environments, and the other a pantropical lineage spanning multiple continents. Abutilon grandifolium was recovered as sister to the remaining sampled Abutilon taxa in both ML and BI analyses, although no biogeographic origin inference can be drawn from this placement pending broader taxon sampling and integration of nuclear genomic data. These findings provide insights into the evolutionary dynamics of the cp. genome in Abutilon and offer a foundational genomic framework for refining Abutilon taxonomy.

Genome, Chloroplast

Cyclopropene fatty acids of selected seed oils from bombacaceae, malvaceae, and sterculiaceae.

Fatty acid compositions of seed oils from three species of Bombacaceae, eleven from Malvaceae, and six from Sterculiaceae were determined. Each of the seed oils contains varying amounts of both malvalic and sterculic acids accompanied by one or both of the corresponding cyclopropane fatty acids. In addition, the seed oil of Pachira aquatic Aubl. (Bombacaceae) contains 12.8% alpha-hydroxysterculic acid.

Cyclopropanes

Tumor-inhibitory agent from Montezuma speciosissima (Malvaceae).

The petroleum ether extract of Montezuma speciosissima Sesse and Moc. demonstrated tumor-inhibiting properties in the P-338 lympocytic leukemia test system (3PS). The constituent responsible for this activity was shown to be a symmetrically substituted 2,2'-dinaphthol, identified as gossypol (C30H30O8).

Animals

Complete telomere-to-telomere genome assembly of Guazuma ulmifolia uncovers evolutionary mechanisms, drought adaptation, and flavonoid biosynthesis.

The first T2T reference genome of Guazuma ulmifolia is reported, which serves as a core genomic resource for stress adaptation research and stress-tolerant breeding in cacao wild relatives. Climate change, particularly increased incidence of drought, poses a major threat to food security. Understanding the genomic basis of environmental adaptation in crop wild relatives can provide valuable resources for improving stress resilience. Guazuma ulmifolia, a wild relative of Theobroma cacao with important ecological and medicinal value, lacks high-quality reference genomic resources. Here, we report the first telomere-to-telomere (T2T) chromosome-level genome assembly of G. ulmifolia, with a genome size of 311.31 Mb, contig N50 of 35.19 Mb, and 98.70% BUSCO completeness. Repetitive sequences constitute 27.43% of the G. ulmifolia genome, with LTR retrotransposons as the predominant class. Comparative genomic analyses revealed that genome-size variation among Malvaceae species is associated with differences in polyploidization history and TE dynamics. Ancestral karyotype reconstruction identified five lineage-specific chromosome fusion events distinguishing G. ulmifolia from T. cacao. Comparative analyses further identified tandem duplication-associated expansion of stress-related LEA and GST gene families, suggesting potential genomic features associated with stress responses. Flavonoid biosynthesis genes were largely conserved in copy number but showed tissue-specific expression patterns, providing candidate genes for investigating secondary metabolism. Together, this study establishes a high-quality T2T genome resource for exploring genome evolution, chromosome organization, and stress-related genomic features in Malvaceae.

Genome, Plant

A telomere-to-telomere reference genome assembly of the red silk cotton tree (Bombax ceiba).

Bombax ceiba, an important ornamental tree and potential fiber resource in the textile industry, is widely distributed in tropical and subtropical regions. In this study, we assembled a nearly gap-free telomere-to-telomere (T2T) genome of B. ceiba using Illumina, PacBio High-fidelity (HiFi), ONT ultra-long, and Hi-C sequencing technologies. The genome spanned approximately 807.89 Mb, with a scaffold N50 of 16.58 Mb, and 754.68 Mb (93.41%) of genomic sequences were anchored onto 48 pseudo-chromosomes. Benchmarking Universal Single-Copy Orthologs (BUSCO) analysis revealed a completeness of 99.40%, identifying 1,378 single-copy and 213 duplicated genes out of 1,614. The genome contained 67.72% (547.11 Mb) repeat regions, with 39,708 predicted protein-coding genes. Collectively, our study provides valuable genomic data for investigating the evolutionary history of the Malvaceae family.

Genome, Plant

Effects of an aqueous extract of cotton seed (Gossypium barbadense Linn.) on adult male rats.

Twenty adult male rats per group in 4 treatment groups were injected intraperitoneally at 08.00 hours with 0.1 ml of an aqueous cotton seed extract (Gossypium barbadense Linn.) (Malvaceae) in concentrations of (a) 105.25, (b) 21.21, (c) 4.65, (d) 2.325 mg ml-1 (kg body weight)-1, respectively. A fifth group (control) was given 0.1 ml of pyrogen free distilled water per rat. Five rats per treatment group were sacrificed at 2, 8, 24 and 168 hours respectively after treatment. Plasma follicle stimulating hormone (FSH) and luteinizing hormone (LH) showed no change. Plasma testosterone was lower (p less than 0.05) than that of control at 2 and 8 hours, with recovery by 168 hours post treatment. Plasma creatinine was raised by 2 hours, with recovery by 8 hours. Plasma urea rose gradually but persistently to a maximum of 168 hours. Plasma aspartate (AST) and alanine (ALT) transaminases were significantly higher (p less than 0.001) than that of controls throughout the study. Testicular histology showed early germ cell disorganization followed by progressive fibrosis (sperm cytoskeleton) by 24 hours. There was evidence of recovery by 168 hours. It is concluded that aqueous extract of cotton seed meal contains substances that can rapidly cause damage to testicular, liver, kidney and muscular tissues.

Animals

Chromosome-level genome assembly of the ornamental plant Alcea rosea.

Alcea rosea, a member of the Malvaceae family, is celebrated for its rich floral palette and global horticultural significance. Here, we present a high-quality reference genome for A. rosea, achieving a genome assembly size of 1.01 Gbp, with a Contig N50 length of 36.61 Mbp. The genome sequence was successfully mapped to 21 chromosomes, and the scaffold N50 length reached 52.57 Mbp, with a scaffold genome completeness of 99.6%. A total of 565.84 Mbp (comprising 56% of the genome) of repetitive sequences were identified, with transposable elements being predominant, particularly long terminal repeat (LTR) elements, which accounted for 48.44% of the genome. 51,436 genes were annotated. Among these predicted genes, the average gene length and coding sequence (CDS) length were 2739.92 bp and 1242.54 bp, respectively.

Genome, Plant

Chemical structure and biological activity of polysaccharides from Hibiscus sabdariffa.

Three water-soluble polysaccharides have been isolated from flower buds of Hibiscus sabdariffa L. (HIB 1,2,3). The neutral polysaccharides (HIB 1 and 2) are composed of arabinans and arabinogalactans of low relative molecular mass. The major fraction was investigated by methylation analysis, pectinase-treatment, mild acid hydrolysis and NMR studies, and it was shown to be a pectin-like molecule (Mr = 10(5)d). The main chain is composed of alpha-1,4-linked GalA (24% methyl-esterified) and alpha-1,2-linked Rha. Side chains are built of Gal and Ara and are connected to the main chain via C-4 of every third Rha. Its structure seems to be different from polysaccharide structures described in other species of the Hibiscus genus and the Malvaceae family. All fractions were assayed for possible immune-modulating effects. All fractions showed some activity, but the main acidic fraction was contaminated with lipopolysaccharide, and therefore its shown activity has to be discussed carefully.

Animals

Gene expression in cotton (Gossypium hirsutum L.) fiber: cloning of the mRNAs.

Cotton, an important natural fiber, is a differentiated epidermal cell. The number of genes that are active in fiber cells is similar to those in leaf, ovule, or root tissues. Through differential screening of a fiber cDNA library, we isolated five cDNA clones that are preferentially expressed in fiber. One of the cDNA clones, pCKE6, corresponded to an abundant mRNA in fiber. Transcripts for E6 were detected throughout the development of the fiber. Immunoprecipitation of in vitro translation products and Western blot analysis of fiber proteins showed two polypeptides in the range of 30-32 kDa as the products of E6 mRNA. Sequence analysis and hybrid-selected RNA translation also suggest that E6 mRNAs encode two polypeptides. Concentrations of E6 mRNA and protein are highest during the late primary cell wall and early secondary cell wall synthesis stages. Sequence comparison of E6 with other known eukaryotic and prokaryotic genes reveals no significant homology (GenBank; December 1991). E6 or a homologous gene(s) is conserved in several members of Malvaceae as well as in one other fiber-producing plant, kapok, but is not found in several other plants examined or in Acetobacter xylinum. A genomic clone corresponding to pCKE6 was isolated, and the promoter element of the E6 gene was shown to direct the expression of a carrot extensin mRNA in a tissue-specific and developmentally regulated fashion in transgenic cotton plants.

Amino Acid Sequence

[Biological evaluation of Cuban plants. IV].

Aqueous, alcoholic and ketonic extracts from leaves and stems of plants of the families Malvaceae, Anonaceae, Punicaceae, Verbenaceae and Urticaceae were analyzed in order to prove their antibacterial proprieties. The best results were obtained from Punica granatum extracts which inhibited over a 50% of bacteria.

Anti-Bacterial Agents