Fruit set is an essential process to ensure successful sexual plant reproduction. The development of the flower into a fruit is actively repressed in the absence of pollination. However, some ...cultivars from a few species are able to develop seedless fruits overcoming the standard restriction of unpollinated ovaries to growth.
We report here the identification of the tomato hydra mutant that produces seedless (parthenocarpic) fruits.
Seedless fruit production in hydra plants is linked to the absence of both male and female sporocyte development. The HYDRA gene is therefore essential for the initiation of sporogenesis in tomato. Using positional cloning, virus-induced gene silencing and expression analysis experiments, we identified the HYDRA gene and demonstrated that it encodes the tomato orthologue of SPOROCYTELESS/NOZZLE (SPL/NZZ) of Arabidopsis. We found that the precocious growth of the ovary is associated with changes in the expression of genes involved in gibberellin (GA) metabolism.
Our results support the conservation of the function of SPL-like genes in the control of sporogenesis in plants. Moreover, this study uncovers a new function for the tomato SlSPL/HYDRA gene in the control of fruit initiation.
Summary
Pollen development is a crucial step in higher plants, which not only makes possible plant fertilization and seed formation, but also determines fruit quality and yield in crop species. Here, ...we reported a tomato T‐DNA mutant, pollen deficient1 (pod1), characterized by an abnormal anther development and the lack of viable pollen formation, which led to the production of parthenocarpic fruits. Genomic analyses and the characterization of silencing lines proved that pod1 mutant phenotype relies on the tomato SlMED18 gene encoding the subunit 18 of Mediator multi‐protein complex involved in RNA polymerase II transcription machinery. The loss of SlMED18 function delayed tapetum degeneration, which resulted in deficient microspore development and scarce production of viable pollen. A detailed histological characterization of anther development proved that changes during microgametogenesis and a significant delay in tapetum degeneration are associated with a high proportion of degenerated cells and, hence, should be responsible for the low production of functional pollen grains. Expression of pollen marker genes indicated that SlMED18 is essential for the proper transcription of a subset of genes specifically required to pollen formation and fruit development, revealing a key role of SlMED18 in male gametogenesis of tomato. Additionally, SlMED18 is able to rescue developmental abnormalities of the Arabidopsis med18 mutant, indicating that most biological functions have been conserved in both species.
Significance Statement
Pollination is a key development process in the life cycle of flowering plants. Genetic and molecular characterization of a tomato mutant have led to the identification of POD1 gene encoding the Mediator complex subunit MED18 whose function is required for tapetum tissue degeneration, a crucial step for pollen development. Furthermore, we show that MED18 fulfils an essential role in tomato, ensuring proper gene regulation during pollen ontogeny.
Summary
A screening under salt stress conditions of a T‐DNA mutant collection of tomato (Solanum lycopersicum L.) led to the identification of the altered response to salt stress 1 (ars1) mutant, ...which showed a salt‐sensitive phenotype. Genetic analysis of the ars1 mutation revealed that a single T‐DNA insertion in the ARS1 gene was responsible of the mutant phenotype. ARS1 coded for an R1‐MYB type transcription factor and its expression was induced by salinity in leaves. The mutant reduced fruit yield under salt acclimation while in the absence of stress the disruption of ARS1 did not affect this agronomic trait. The stomatal behaviour of ars1 mutant leaves induced higher Na+ accumulation via the transpiration stream, as the decreases of stomatal conductance and transpiration rate induced by salt stress were markedly lower in the mutant plants. Moreover, the mutation affected stomatal closure in a response mediated by abscisic acid (ABA). The characterization of tomato transgenic lines silencing and overexpressing ARS1 corroborates the role of the gene in regulating the water loss via transpiration under salinity. Together, our results show that ARS1 tomato gene contributes to reduce transpirational water loss under salt stress. Finally, this gene could be interesting for tomato molecular breeding, because its manipulation could lead to improved stress tolerance without yield penalty under optimal culture conditions.
Reproductive development of higher plants comprises successive events of organ differentiation and growth which finally lead to the formation of a mature fruit. However, most of the genetic and ...molecular mechanisms which coordinate such developmental events are yet to be identified and characterized. Arlequin (Alq), a semi-dominant T-DNA tomato mutant showed developmental changes affecting flower and fruit ripening. Sepals were converted into fleshy organs which ripened as normal fruit organs and fruits displayed altered ripening features. Molecular characterization of the tagged gene demonstrated that it corresponded to the previously reported tomato Agamous-like 1 (TAGL1) gene, the tomato ortholog of shatterproof MADS-box genes of Arabidopsis thaliana, and that the Alq mutation promoted a gain-of-function phenotype caused by the ectopic expression of TAGL1. Ectopic overexpression of TAGL1 resulted in homeotic alterations affecting floral organ identity that were similar to but stronger than those observed in Alq mutant plants. Interestingly, TAGL1 RNAi plants yielded tomato fruits which were unable to ripen. They displayed a yellow-orange color and stiffness appearance which are in accordance with reduced lycopene and ethylene levels, respectively. Moreover, pericarp cells of TAGL1 RNAi fruits showed altered cellular and structural properties which correlated to both decreased expression of genes regulating cell division and lignin biosynthesis. Over-expression of TAGL1 is able to rescue the non-ripening phenotype of rin and nor mutants, which is mediated by the transcriptional activation of several ripening genes. Our results demonstrated that TAGL1 participates in the genetic control of flower and fruit development of tomato plants. Furthermore, gene silencing and over-expression experiments demonstrated that the fruit ripening process requires the regulatory activity of TAGL1. Therefore, TAGL1 could act as a linking factor connecting successive stages of reproductive development, from flower development to fruit maturation, allowing this complex process to be carried out successfully.
Summary
With the completion of genome sequencing projects, the next challenge is to close the gap between gene annotation and gene functional assignment. Genomic tools to identify gene functions are ...based on the analysis of phenotypic variations between a wild type and its mutant; hence, mutant collections are a valuable resource. In this sense, T‐DNA collections allow for an easy and straightforward identification of the tagged gene, serving as the basis of both forward and reverse genetic strategies. This study reports on the phenotypic and molecular characterization of an enhancer trap T‐DNA collection in tomato (Solanum lycopersicum L.), which has been produced by Agrobacterium‐mediated transformation using a binary vector bearing a minimal promoter fused to the uidA reporter gene. Two genes have been isolated from different T‐DNA mutants, one of these genes codes for a UTP‐glucose‐1‐phosphate uridylyltransferase involved in programmed cell death and leaf development, which means a novel gene function reported in tomato. Together, our results support that enhancer trapping is a powerful tool to identify novel genes and regulatory elements in tomato and that this T‐DNA mutant collection represents a highly valuable resource for functional analyses in this fleshy‐fruited model species.
Tranchant, Mathias, Le ports maritimes de la France atlantique (XIe-XVe siècle). Volume I: Tableau géohistorique, Presses Universitaires de Rennes, Rennes, 2017. 261 págs. isbn 978-2-7535-5533-4.
El consenso establece las diferentes ventajas y limitaciones de los sistemas de monitorización hemodinámica. Además establece 10 recomendaciones de monitorización hemodinámica en el paciente crítico:
...1.- Ningún tipo de monitorización hemodinámica por sí sola modifica los resultados.
2.- Los resultados obtenidos de la monitorización pueden variar en el tiempo y dependen de la disponibilidad del equipo y del entrenamiento del personal.
3.- Los valores hemodinámicos no son aplicables a todos los pacientes.
4.- Para una correcta monitorización son necesarios la combinación e integración de varias variables.
5.- La medida de la SvO2 puede ser de ayuda.
6.- Los valores supraóptimos de gasto cardiaco y de SvO2 no siempre son beneficiosos.
7.- El gasto cardiaco derivado de los dispositivos de monitorización es estimado.
8.- Los cambios que se producen en la monitorización a lo largo del tiempo son importantes.
9.- La medición continua de las variables hemodinámicas es preferible.
10.- Aunque es preferible, el ser menos invasivo no es el único objetivo.
El estatus epiléptico (EE) es una emergencia neurológica que debe ser tratada de manera precoz para disminuir su elevada morbi-mortalidad. La monitorización de la actividad cortical es esencial en el ...manejo del EE. La monitorización EEG continua diagnostica actividad crítica e intercrítica, grafoelementos epileptiformes, evalúa la profundidad anestésica y ofrece patrones pronósticos. Su limitada disponibilidad y la complejidad de su interpretación hace del BIS (Bispectral Index Signal) una herramienta más sencilla para la monitorización de la profundidad del coma inducido.
Entre ellos, localiza los puertos más complejos (aquellos que tuvieron mayor actividad pesquera, portuaria y comercial) como fueron Bayona, Burdeos, La Rochelle, Nantes, Harfleur, Rouen y Brujas. En ...términos globales, el mar Atlántico fue el motor de desarrollo de los centros urbanos, de mayores o menores dimensiones, en la zona objeto de estudio. La obra de Mathias Tranchant resulta ser un libro excelente, de gran utilidad tanto para investigadores como para estudiantes de máster y doctorado que dediquen sus esfuerzos, principalmente, a los espacios portuarios de la costa francófona en la Edad Media.
Summary
Pollen development is a crucial step in higher plants, which not only makes possible plant fertilization and seed formation, but also determines fruit quality and yield in crop species. Here, ...we reported a tomato T‐
DNA
mutant,
pollen deficient1
(
pod1
), characterized by an abnormal anther development and the lack of viable pollen formation, which led to the production of parthenocarpic fruits. Genomic analyses and the characterization of silencing lines proved that
pod1
mutant phenotype relies on the tomato
Sl
MED
18
gene encoding the subunit 18 of Mediator multi‐protein complex involved in
RNA
polymerase
II
transcription machinery. The loss of
Sl
MED
18
function delayed tapetum degeneration, which resulted in deficient microspore development and scarce production of viable pollen. A detailed histological characterization of anther development proved that changes during microgametogenesis and a significant delay in tapetum degeneration are associated with a high proportion of degenerated cells and, hence, should be responsible for the low production of functional pollen grains. Expression of pollen marker genes indicated that
Sl
MED
18
is essential for the proper transcription of a subset of genes specifically required to pollen formation and fruit development, revealing a key role of
Sl
MED
18
in male gametogenesis of tomato. Additionally,
Sl
MED
18
is able to rescue developmental abnormalities of the Arabidopsis
med18
mutant, indicating that most biological functions have been conserved in both species.
Significance Statement
Pollination is a key development process in the life cycle of flowering plants. Genetic and molecular characterization of a tomato mutant have led to the identification of
POD
1
gene encoding the Mediator complex subunit
MED
18 whose function is required for tapetum tissue degeneration, a crucial step for pollen development. Furthermore, we show that
MED
18 fulfils an essential role in tomato, ensuring proper gene regulation during pollen ontogeny.
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