1,721,034 research outputs found
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
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
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
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”
The disbudding (nipping) x genotype interaction demonstrates different perennial habits in castor-oil plant (Ricinus communis L.).
No full textIn castor-oil plant the perennial habit contrasts with the combine harvester. A hypothetical non-branching annual castor plant is based on the stop of the meristem activity in the axillary buds and/or in the cambium. To investigate the relationship between the cambial activity and the axillary bud outgrowth, an experiment on the axillary bud excision was carried out in the field with 64 inbred lines. The stems of treated plants were disbudded, while, as control, the same number of plants was untreated. At the harvest of the first raceme, the treated plants had obviously only the main stem whereas the control plants resulted normally branched. The disbudding treatment heavily affected the stem diameter and interacted with the genotypes. The seed production and the 1000-seed weight were significantly affected by the disbudding treatment. This research, aimed at solving a cultivation problem, can also contribute to better know the semelparity in plants
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 textGenetic and physiological characterization of a new brachytic sunflower mutant, lingering hope (linho).
No full textDwarf mutants in plants are crucial to elucidate regulatory mechanisms for plant growth and development. A new dwarf mutant named lingering hope (linho) was isolated from sunflower (Helianthus annuus). With the aim to characterize this new brachytic mutant, we performed genetic analysis and several morphometric data were collected. The hormonal profile and the photosynthetic performance were also investigated in this mutant. The brachytic trait is controlled by a recessive nuclear gene. The reduction of plant height is not due to the production of fewer phytomers but the phenotype depends on shorter internodes especially during reproductive stage.
The mutant and wild type (WT) phenotype is normal from the cotyledonary stage to the first two pairs of leaves. However, after this vegetative stage, linho leaves show an altered ratio length/width of the blade, delayed greening phenomena and chlorosis in proximal area of the lamina; moreover, asymmetric shape and epinasty have been frequently observed. The linho mutant has defects in inflorescence development because blossoming is not regular. In several organs of linho and WT we analyzed endogenous hormonal level of abscisic acid, jasmonic acid, indoleacetic acid, salicylic
acid (SA) and gibberellins. Results demonstrate that the brachytic trait is not associated to a specific hormonal reduction but the endogenous SA content in some organs (i.e. young leaves in reproductive stage) of the mutant is very high. SA plays key role in plant response to abiotic and biotic stresses although SA effects on plant growth and development are very complex and not still well understood. To evaluate the photosynthetic performance and the light energy dissipation mechanisms, gas exchange and fluorescence measurements were determined in linho and WT
plants. The CO 2 assimilation rate significantly decreased in linho, due to the effects of both stomatal and non-stomatal constraints. In addition, the reduction of both photochemical efficiency of photosystem II and non-photochemical quenching at saturating light intensity indicated a lower capacity of linho to dissipate the absorbed light energy, associated with a reduced content of chlorophylls and carotenoids. These results suggest that the linho mutant could be useful to investigate the role of SA during plant growth and developmen
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