1,721,080 research outputs found
The dynamic genetic-hormonal regulatory network controlling the trichome development in leaves
Full text linkPlant trichomes are outgrowths developed from an epidermal pavement cells of leaves and other organs. Trichomes (also called 'hairs') play well-recognized roles in defense against insect herbivores, forming a physical barrier that obstructs insect movement and mediating chemical defenses. In addition, trichomes can act as a mechanosensory switch, transducing mechanical stimuli (e.g., insect movement) into physiological signals, helping the plant to respond to insect attacks. Hairs can also modulate plant responses to abiotic stresses, such as water loss, an excess of light and temperature, and reflect light to protect plants against UV radiation. The structure of trichomes is species-specific and this trait is generally related to their function. These outgrowths are easily analyzed and their origin represents an outstanding subject to study epidermal cell fate and patterning in plant organs. In leaves, the developmental control of the trichomatous complement has highlighted a regulatory network based on four fundamental elements: (i) genes that activate and/or modify the normal cell cycle of epidermal pavement cells (i.e., endoreduplication cycles); (ii) transcription factors that create an activator/repressor complex with a central role in determining cell fate, initiation, and differentiation of an epidermal cell in trichomes; (iii) evidence that underlines the interplay of the aforesaid complex with different classes of phytohormones; (iv) epigenetic mechanisms involved in trichome development. Here, we reviewed the role of genes in the development of trichomes, as well as the interaction between genes and hormones. Furthermore, we reported basic studies about the regulation of the cell cycle and the complexity of trichomes. Finally, this review focused on the epigenetic factors involved in the initiation and development of hairs, mainly on leaves
Sequence analysis and expression profile of a PINOID-LIKE gene in organs of sunflower (Helianthus annuus L.) and in the missing flowers mutant
No full textThe temporal and spatial distribution of the auxin is determined by the polar subcellular localization of PIN-FORMED (PIN) auxin efflux carrier family. Phosphorylation dynamics of PIN proteins are affected by the protein phosphatase 2A and the Ser/Thr protein kinase PINOID (PID). A PID-LIKE (Ha-PIDL) gene has been isolated in sunflower also to perform a candidate-gene approach for the mutant missing flowers (mf). Sequence and phylogenetic analyses suggested that Ha-PIDL was the orthologs of the PID transcript. Real-Time Quantitative Reverse Transcription PCR analysis revealed a high accumulation of Ha-PIDL transcripts in vegetative shoots and inflorescence shoots of sunflower. In addition, sequence and transcriptional analyses suggested that the phenotype of the mf mutant was not due to a mutation and/or altered transcription of Ha-PIDL. Nevertheless, the isolation and characterization of a PID-LIKE gene should be critical to study the polar auxin transport i
Transposable elements in the evolution of floral shape and inflorescence architecture
Full text linkTransposable elements (TEs) are ubiquitous in the plant kingdom and can be a major component of plant genomes. TEs are DNA sequences that can change their position within genomes. Transposition of TEs can influence plant genes and genomes in many ways. TEs can restructure genomes through element-mediated chromosomal rearrangements and alter the genome size thus acting as agents of genome evolution. They also cause mutations by insertion into genes and affect the regulation of genes by inserting near promoters. There are some examples of mutations and other types of genetic variations associated with the activity of mobile elements and involved in flower development. The origin and extremely rapid diversification of flowering plants, which Darwin famously referred to as an “abominable mystery,” is one of the most extraordinary phenomena in evolutionary history. The most extensive manifestation of this morphological variability is found in the innumerable and surprising flower structures in plants adapted to the most contrasting environments. The wide floral diversification is a consequence of the arrangement of the organs (sepals, petals, stamens and carpels) in the four whorls of flowers and the shape that the various organs take, in particular the petal symmetry both in the individual flowers and in the organization of the inflorescences. This review will focus on how the activity of TEs has altered the activity of some genes controlling floral shape and inflorescence architecture in angiosperms
Presence/absence of a CACTA transposon in the CYC2c gene of two genotypes of Helianthus × multiflorus cv. “Meteor” characterized by a radiate inflorescence with different shape of disk flower corollas
No full textHelianthus × multiflorus is a triploid (2n = 51) interspecific hybrid derived from the cross of H. decapetalus with H. annuus that exists in radiate and ligulate inflorescence types. The H. × multiflorus “Soleil d’Or” has a ligulate inflorescence, with actinomorphic corolla of disk flowers converted in zygomorphic ray-like corollas. In “Soleil d’Or”, a truncated CACTA transposable element (TE), named CTEHM1, is integrated in the HmCYC2c gene, a key player controlling zygomorphism in the Helianthus genus. Here, we showed that H. × multiflorus “Meteor”, originated from a mutation of “Soleil d’Or”, exists in two different types of radiate inflorescence, here named “Meteor 1” and “Meteor 2”. Notably, in “Meteor 1”, which displayed a corolla of disk flowers typical for the Helianthus genus, CTEHM1 was transposed from the HmCYC2c gene. In contrast, the CTEHM1 TE was still present in the HmCYC2c gene of “Meteor 2”. In this genotype, the largest corolla of the disk flowers shows some features of the ray flowers giving rise to a radiate inflorescence unusual for the Helianthus genus. The in silico analysis of CTEHM1 also highlights the presence of a 202 bp CpNpG island, which is a putative target of methylation. Interestingly, the gene expression of the HmCYC2c gene was significantly higher in disk flowers of “Meteor 2” compared to “Meteor 1”. Stated these results, we suggest that both the excision of a TE and an epigenetic regulation of gene expression generate the two-inflorescence types of H. × multiflorus, “Meteor 1” and “Meteor 2”
Risk factors for developing endometrial cancer after benign endometrial sampling
No full textMissed opportunities for primary endometrial cancer prevention: how to optimize early identification and treatment of high-risk women. [Obstet Gynecol. 2012]
Risk factors for developing endometrial cancer after benign endometrial sampling. [Obstet Gynecol. 2012
A transposon-mediate inactivation of a CYCLOIDEA-like gene originates polysymmetric and androgynous ray flowers in Helianthus annuus
No full textn several eudicots, including members of the Asteraceae family, the CYCLOIDEA (CYC) genes, which belong to the TCP class of transcription factors, are key players for floral symmetry. The sunflower inflorescence is heterogamous (radiate capitulum) with sterile monosymmetric ray flowers located in the outermost whorl of the inflorescence and hermaphrodite polysymmetric disk flowers. In inflorescence of Heliantheae tribe, flower primordia development initiates from the marginal ray flowers while disk flowers develop later in an acropetal fashion in organized parastichies along a number found to be one of Fibonacci patterns. Mutants for inflorescence morphology can provide information on the role of CYC-like genes in radiate capitulum evolution. The tubular ray flower (turf) mutant of sunflower shows hermaphrodite ray flowers with a nearly polysymmetric tubular-like corolla. Here, we demonstrate that this mutation is caused by the insertion in the TCP motif of a sunflower CYC-like gene (HaCYC2c) of non-autonomous transposable element (TE), belonging to the CACTA superfamily of transposons. We named this element Transposable element of turf1 (Tetu1). The Tetu1 insertion changes the reading frame of turf-HaCYC2c for the encoded protein and leads to a premature stop codon. Although in Tetu1 a transposase gene is lacking, our results clearly suggest that it is an active TE. The excision of Tetu1 restores the wild type phenotype or generates stable mutants. Co-segregation and sequence analysis in progenies of F(2) and self-fertilized plants derived from reversion of turf to wild type clearly identify HaCYC2c as a key regulator of ray flowers symmetry. Also, HaCYC2c loss-of-function promotes the developmental switch from sterile to hermaphrodite flowers, revealing a novel and unexpected role for a CYC-like gene in the repression of female organs
Erinea in the 'Ansonica' grapevine cultivar: Trichome complement, histological effects and analysis of chlorophyll fluorescence in affected leaves
No full textGrapevine leaves are usually characterized by trichomes, specialized epidermal cells. They are interesting in ampelography and also important for the plant ecological responses in biotic and abiotic interactions. In nature, the trichome development is a genetic trait but it can be modified by pests as eriophyid mites. Colomerus vitis is quite common and its economic value is sometime substantial. Here, we studied the leaf erineum induced by C. vitis on 'Ansonica' ('Inzolia'), an important grapevine cultivar characterized by a low level of leaf trichome coating. To date, the interaction between C. vitis and grape has been investigated in few pedo-climatic conditions and no data are reported in 'Ansonica'. Therefore, our objectives were: (1) the analysis, in a Tuscan environment, of the morphology and histology of trichomes in 'Ansonica' leaves unaffected or affected by C. vitis; (2) evaluation, in mature leaves, of the effects of the mite both on pigment content and chlorophyll a fluorescence parameters. 'Ansonica' was devoid of glandular trichomes but it has been established the presence of few simple trichomes strictly associated with the veins. In the erineal sectors, a dense proliferation of simple trichomes in the abaxial epidermis and the development of hyperplasia in the adaxial surface were observed. Moreover, the leaf sections in the erineal regions were thicker due to an abnormal development of the lacunar parenchyma, and trichome proliferation was also extended to interveinal regions. Leaves with erinea showed a deficient content of carotenoids, in comparison to unaffected leaves. In 'Ansonica' leaves, C. vitis induced a decrease in the steady-state operational efficiency of photosystem II associated to a reduction in photochemical quenching and an increase in non-photochemical quenching values. In leaves with erinea, the reduction of photosystem II efficiency was extended to foliar areas not directly affected by galls. The collected results highlight that 'Ansonica' is susceptible to attacks by C. vitis and in the case of widespread leaf attacks the productive damage should not be underestimated
Ray flower initiation in the Helianthus radula inflorescence is influenced by a functional allele of the HrCYC2c gene
No full textThe radiate pseudanthium, with actinomorphic disk flowers surrounded by showy marginal zygomorphic ray flowers, is the most common inflorescence in the Helianthus genus. In Helianthus radula, ray flower primordia are normally absent at the dorsal domain of the inner phyllaries (discoid heads) while the occurrence of radiate inflorescences is uncommon. In Helianthus spp., flower symmetry and inflorescence architecture are mainly controlled by CYCLOIDEA (CYC)-like genes but the putative role of these genes in the development of discoid inflorescences has not been investigate. Three CYC genes of H. radula with a role in ray flower identity (HrCYC2c, HrCYC2d, and HrCYC2e) were isolated. The phylogenetic analysis placed these genes within the CYC2 subclade. We identified two different alleles for the HrCYC2c gene. A mutant allele, designed HrCYC2c-m, shows a thymine to adenine transversion, which generates a TGA stop codon after a translation of 14 amino acids. We established homozygous dominant (HrCYC2c/HrCYC2c) and recessive (HrCYC2c-m/HrCYC2c-m) plants for this nonsense mutation. Inflorescences of both HrCYC2c/HrCYC2c and HrCYC2c/HrCYC2c-m plants initiated ray flowers, despite at low frequency. By contrast, plants homozygous for the mutant allele (HrCYC2c-m/HrCYC2c-m) failed at all to develop ray flowers. The results support, for the first time, a role of the HrCYC2c gene on the initiation of ray flower primordia. However, also in the two dominant phenotypes, discoid heads are the prevalent architecture suggesting that this gene is required but not sufficient to initiate ray flowers in pseudanthia. Other unknown major genes are most likely required in the shift from discoid to radiate inflorescence
In the turf mutant of sunflower, a transposon insertion in a Cycloidea gene (HaCYC2c) changes the floral symmetry and fertility of ray flowers
No full textThe plastic genome: The impact of transposable elements on gene functionality and genomic structural variations
No full textTransposable elements (TEs) are DNA sequences that can change their position within genomes. TEs are present in most organisms and can be an important genomic component. Their activities are manifold: restructuring of genome size, chromosomal rearrangements, induction of gene mutations, and alteration of gene activity by insertion near or within promoters, intronic regions, or enhancer. There are several examples of mutations and other genetic variations determined by the activity of TEs, associated with the evolution of prokaryotic and eukaryotic organisms and the domestication of plants. Generally, TE mobilization occurs when the organism is subjected to stress, which can include both biotic and abiotic stresses, polyploidy conditions, and interspecific hybridizations, very common events in plants. TEs are widely distributed among organisms. TEs also play essential roles in evolution, but most of them are either dormant or inactive. This is mainly determined by epigenetic silencing mechanisms, regulatory systems, and control systems that aim to limit its proliferation. Furthermore, the host has recruited many genes originated from TEs as transcriptional regulators, especially in defense against pathogens and invasive genetic elements; this phenomenon is called molecular domestication. Therefore, TEs are responsible for horizontal gene transfer and the movement of genetic material between organisms, even phylogenetically distant, with a consequent remixing of their gene pools
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