Involvement of ethylene biosynthesis and signalling in fruit set and early fruit development in zucchini squash (Cucurbita pepo L.)

Background We have identified a kind of parthenocarpy in zucchini squash which is associated with an incomplete andromonoecy, i.e. a partial conversion of female into bisexual flowers. Given that andromonoecy in this and other cucurbit species is caused by a reduction of ethylene production in the female flower, the associated parthenocarpic development of the fruit suggested the involvement of ethylene in fruit set and early fruit development.Results We have compared the production of ethylene as well as the expression of 13 ethylene biosynthesis and signalling genes in pollinated and unpollinated ovaries/fruits of two cultivars, one of which is parthenocarpic (Cavili), while the other is non-parthenocarpic (Tosca). In the latter, unpollinated ovaries show an induction of ethylene biosynthesis and ethylene signal transduction pathway genes three days after anthesis, which is concomitant with the initiation of fruit abortion and senescence. Fruit set and early fruit development in pollinated flowers of both cultivars and unpollinated flowers of Cavili is coupled with low ethylene biosynthesis and signalling, which would also explain the partial andromonoecy in the parthenocarpic genotype. The reduction of ethylene production in the ovary cosegregates with parthenocarpy and partial andromonoecy in the selfing progeny of Cavili. Moreover, the induction of ethylene in anthesis (by ethephon treatments) reduced the percentage of bisexual parthenocarpic flowers in Cavili, while the inhibition of ethylene biosynthesis or response (by AVG and STS treatments) induces not only andromonoecy but also the parthenocarpic development of the fruit in both cultivars.Conclusions Results demonstrate that a reduction of ethylene production or signalling in the zucchini flower is able to induce fruit set and early fruit development, and therefore that ethylene is actively involved in fruit set and early fruit development. Auxin and TIBA treatments, inducing fruit set and early fruit development in this species, also inhibit ethylene production and the expression of ethylene biosynthesis and response genes. A model is presented that discusses the crosstalk between ethylene and auxin in the control of fruit set and early fruit development in zucchini squash.This work was supported by grants AGL2008-05619-C02-02/ALI and AGL2011-30568-C02-02/ALI, partly funded by ERDF (European Regional Development Fund) and by the Spanish Ministry of Science and Innovation, and grant CVI-02617, funded by ERDF and by the Consejería de Innovación, Ciencia y Empresa, Junta de Andalucía, Spain. C.M. and Z.M. acknowledge FPU program scholarships from MEC, Spain. S.M. is funded by grant PTA2011-479-I from the Spanish Ministry of Science and Innovation

Individual Shrink Wrapping of Zucchini Fruit Improves Postharvest Chilling Tolerance Associated with a Reduction in Ethylene Production and Oxidative Stress Metabolites

We have studied the effect of individual shrink wrapping (ISW) on the postharvest performance of refrigerated fruit from two zucchini cultivars that differ in their sensitivity to cold storage: Sinatra (more sensitive) and Natura (more tolerant). The fruit was individually shrink wrapped before storing at 4°C for 0, 7 and 14 days. Quality parameters, ethylene and CO2 productions, ethylene gene expression, and oxidative stress metabolites were assessed in shrink wrapped and non-wrapped fruit after conditioning the fruit for 6 hours at 20°C. ISW decreased significantly the postharvest deterioration of chilled zucchini in both cultivars. Weight loss was reduced to less than 1%, pitting symptoms were completely absent in ISW fruit at 7 days, and were less than 25% those of control fruits at 14 days of cold storage, and firmness loss was significantly reduced in the cultivar Sinatra. These enhancements in quality of ISW fruit were associated with a significant reduction in cold-induced ethylene production, in the respiration rate, and in the level of oxidative stress metabolites such as hydrogen peroxide and malonyldialdehyde (MDA). A detailed expression analysis of ethylene biosynthesis, perception and signaling genes demonstrated a downregulation of CpACS1 and CpACO1 genes in response to ISW, two genes that are upregulated by cold storage. However, the expression patterns of six other ethylene biosynthesis genes (CpACS2 to CpACS7) and five ethylene signal transduction pathway genes (CpCTR1, CpETR1, CpERS1, CpEIN3.1 and CpEN3.2), suggest that they do not play a major role in response to cold storage and ISW packaging. In conclusion, ISW zucchini packaging resulted in improved tolerance to chilling concomitantly with a reduction in oxidative stress, respiration rate and ethylene production, as well as in the expression of ethylene biosynthesis genes, but not of those involved in ethylene perception and sensitivity.This work was supported by grants AGL2011-30568-C02/ALI from the Spanish Ministry of Science and Innovation, and AGR1423 from the Consejería de Economía, Innovación y Ciencia, Junta de Andalucía, Spain. Z.M. acknowledges FPU program scholarships from MEC, Spain. S.M. is funded by grant PTA2011-479-I from the Spanish Ministry of Science and Innovation

Análisis de metodologías de evaluación de sistemas de diálogo multimodal

Los sistemas de diálogo multimodal constituyen un campo de investigación de gran interés en la actualidad, pues mejoran notablemente la interacción proporcionada por los sistemas de diálogo oral. Este artículo presenta, de forma resumida, el resultado de un amplio y profundo estudio con el que hemos pretendido conocer cómo se pueden evaluar tales sistemas, y en qué se diferencia esta evaluación de la realizada con sistemas de diálogo oral. Las conclusiones del estudio indican que no existen unos métodos claramente aceptados por la comunidad científica que puedan considerarse estándares de evaluación. Ello sumado a la gran diversidad de tareas y diferencias de complejidad de unos sistemas frente a otros, dificulta en gran medida la comparación de los sistemas de una forma objetiva. Por consiguiente, son necesarias técnicas estándar que faciliten la evaluación teniendo en cuenta las características específicas de cada sistema, así como métodos que faciliten la comparación de sistemas diseñados para tareas diferentes.Multimodal dialogue systems represent a very challenging research field nowadays, as they enhance the interaction provided by spoken dialogue systems. This paper presents, in a summarised way, the results of a wide and deep study we have carried out to try to find the cues for the evaluation of these systems, as well as the main differences in comparison with the evaluation of spoken dialogue systems. Our conclusions indicate there are no methods clearly accepted by the scientific community that can be considered as evaluation standards. This fact, together with the diversity of tasks and differences in the system complexity, makes it very difficult to compare systems objectively. Thus, new techniques are necessary to ease the evaluation taking into account the specific features of each system, as well as new methods to compare systems designed for different tasks

Implementación de sistemas de diálogo en Dial-XML

Dial-XML (Análisis y Aplicación de Tecnologías Basadas en XML para la Implementación de Sistemas de Diálogo) es un proyecto de investigación financiado por el Plan Propio de Investigación de la Univ. de Granada para el año 2005. El principal objetivo del proyecto es facilitar la creación de una infraestructura básica que permita estudiar, analizar e implementar sistemas de diálogo oral, multilingüe y multimodal usando tecnologías basadas en XML, concretamente VoiceXML, CCXML y XHTML+Voice.Dial-XML (Analysis and Application of XML-based Technologies to Set Up Dialogue Systems) is a research project funded by the Research Plan of Granada University for 2005. The project is aimed at facilitating the creation of a basic infrastructure to study, analyse and develop spoken, multimodal and multilingual dialogue using XML-based technologies, concretely VoiceXML, CCXML and XHTML+Voice

The Ethylene Biosynthesis Gene CitACS4 Regulates Monoecy/Andromonoecy in Watermelon (Citrullus lanatus).

Monoecious and andromonoecious cultivars of watermelon are characterised by the production of male and female flower or male and hermaphrodite flowers, respectively. The segregation analysis in the offspring of crosses between monoecious and andromonoecious lines has demonstrated that this trait is controlled by a single gene pair, being the monoecious allele M semi-dominant to the andromonoecious allele A. The two studied F1 hybrids (MA) had a predominantly monoecious phenotype since both produced not only female flowers, but also bisexual flowers with incomplete stamens, and hermaphrodite flowers with pollen. Given that in other cucurbit species andromonoecy is conferred by mutations in the ethylene biosynthesis genes CmACS7, CsACS2 and CpACS27A we have cloned and characterised CitACS4, the watermelon gene showing the highest similarity with the formers. CitACS4 encoded for a type ACS type III enzyme that is predominantly expressed in pistillate flowers of watermelon. In the andromonoecious line we have detected a missense mutation in a very conserved residue of CitACS4 (C364W) that cosegregates with the andromonoecious phenotype in two independent F2 populations, concomitantly with a reduction in ethylene production in the floral buds that will develop as hermaphrodite flowers. The gene does not however co-segregates with other sex expression traits regulated by ethylene in this species, including pistillate flowering transition and the number of pistillate flowers per plant. These data indicate that CitAC4 is likely to be involved in the biosynthesis of the ethylene required for stamen arrest during the development of female flowers. The C364W mutation would reduce the production of ethylene in pistillate floral buds, promoting the conversion of female into hermaphrodite flowers, and therefore of monoecy into andromonoecy

The Ethylene Biosynthesis Gene <i>CitACS4</i> Regulates Monoecy/Andromonoecy in Watermelon (<i>Citrullus lanatus</i>)

<div><p>Monoecious and andromonoecious cultivars of watermelon are characterised by the production of male and female flower or male and hermaphrodite flowers, respectively. The segregation analysis in the offspring of crosses between monoecious and andromonoecious lines has demonstrated that this trait is controlled by a single gene pair, being the monoecious allele <i>M</i> semi-dominant to the andromonoecious allele <i>A</i>. The two studied F1 hybrids (MA) had a predominantly monoecious phenotype since both produced not only female flowers, but also bisexual flowers with incomplete stamens, and hermaphrodite flowers with pollen. Given that in other cucurbit species andromonoecy is conferred by mutations in the ethylene biosynthesis genes <i>CmACS7</i>, <i>CsACS2</i> and <i>CpACS27A</i> we have cloned and characterised <i>CitACS4</i>, the watermelon gene showing the highest similarity with the formers. <i>CitACS4</i> encoded for a type ACS type III enzyme that is predominantly expressed in pistillate flowers of watermelon. In the andromonoecious line we have detected a missense mutation in a very conserved residue of CitACS4 (C364W) that cosegregates with the andromonoecious phenotype in two independent F2 populations, concomitantly with a reduction in ethylene production in the floral buds that will develop as hermaphrodite flowers. The gene does not however co-segregates with other sex expression traits regulated by ethylene in this species, including pistillate flowering transition and the number of pistillate flowers per plant. These data indicate that <i>CitAC4</i> is likely to be involved in the biosynthesis of the ethylene required for stamen arrest during the development of female flowers. The C364W mutation would reduce the production of ethylene in pistillate floral buds, promoting the conversion of female into hermaphrodite flowers, and therefore of monoecy into andromonoecy.</p></div

Sexual expression of watermelon lines P86, P86 and P87 and F1 hybrids derived from crosses P85xP87 and P86xP87.

<p>(A) Phenotype of watermelon hermaphrodite, bisexual, female and male flowers. (B) Distribution of staminate and pistillate flowers in the 20 first nodes of the main shoot. In each node, white, black, green and red bars represent the percentages of male, female, bisexual and hermaphrodite flowers in the total number of plants analysed (n ≥ 10 for each genotype). The lack of bar in a node indicates the absence of flower in that node for some of the analysed plants.</p

Relative expression of <i>CitACS4</i> in different tissues of watermelon cv. Premium.

<p>The values are the average and standard deviation of three biological replicates. St stem, Le leaves, Fe female flowers, Ma male flowers, Bi bisexual flowers. The utilized flowers were at early stages of development (S0).</p

Expression of <i>CitACS4</i> and ethylene production during the development of pistillate flowers in monoecious and andromonoecious lines of watermelon.

<p>(A) Stages of development studied. (B) Relative expression of the gene in female flowers of monoecious (P85 and P86) and in the hermaphrodite flowers of andromonoecious (P87) lines. At S0, the expression corresponds to complete flowers, but in the other stages (S1 to S3), the expression in the ovary was separated to that in the rest of the floral organs (petals, style and stigma, and stamens). (C) Ethylene production in female, hermaphrodite and male flowers of monoecious and andromonoecious lines was measured at earlier developmental stages (S0-S1). Each value is the average from at least three biological replicates. Error bars indicate standard deviation.</p

Segregation ratio of monoecious, partially andromonoecious and andromonoecious plants in F2 populations derived from two crosses between monoecious and andromonoecious inbred lines.

<p>Segregation ratio of monoecious, partially andromonoecious and andromonoecious plants in F2 populations derived from two crosses between monoecious and andromonoecious inbred lines.</p