Showing papers by "Stefan de Folter published in 2018"

New roles of NO TRANSMITTING TRACT and SEEDSTICK during medial domain development in Arabidopsis fruits

Abstract: The gynoecium, the female reproductive part of the flower, is key for plant sexual reproduction. During its development, inner tissues such as the septum and the transmitting tract tissue, important for pollen germination and guidance, are formed. In Arabidopsis, several transcription factors are known to be involved in the development of these tissues. One of them is NO TRANSMITTING TRACT (NTT), essential for transmitting tract formation. We found that the NTT protein can interact with several gynoecium-related transcription factors, including several MADS-box proteins, such as SEEDSTICK (STK), known to specify ovule identity. Evidence suggests that NTT and STK control enzyme and transporter-encoding genes involved in cell wall polysaccharide and lipid distribution in gynoecial medial domain cells. The results indicate that the simultaneous loss of NTT and STK activity affects polysaccharide and lipid deposition and septum fusion, and delays entry of septum cells to their normal degradation program. Furthermore, we identified KAWAK, a direct target of NTT and STK, which is required for the correct formation of fruits in Arabidopsis These findings position NTT and STK as important factors in determining reproductive competence.

Conserved and novel responses to cytokinin treatments during flower and fruit development in Brassica napus and Arabidopsis thaliana.

Abstract: Hormones are an important component in the regulatory networks guiding plant development. Cytokinins are involved in different physiological and developmental processes in plants. In the model plant Arabidopsis thaliana, cytokinin application during gynoecium development produces conspicuous phenotypes. On the other hand, Brassica napus, also known as canola, is a crop plant belonging to the Brassicaceae family, as A. thaliana. This makes B. napus a good candidate to study whether the cytokinin responses observed in A. thaliana are conserved in the same plant family. Here, we observed that cytokinin treatment in B. napus affects different traits of flower and fruit development. It increases ovule and seed number, affects stamen filament elongation and anther maturation, and causes a conspicuous overgrowth of tissue in petals and gynoecia. Furthermore, cytokinin recovers replum development in both wild type B. napus and in the A. thaliana rpl ntt double mutant, in which no replum is visible. These results indicate both conserved and novel responses to cytokinin in B. napus. Moreover, in this species, some cytokinin-induced phenotypes are inherited to the next, untreated generation, suggesting that cytokinins may trigger epigenetic modifications.

Exploring Cell Wall Composition and Modifications During the Development of the Gynoecium Medial Domain in Arabidopsis.

Abstract: In Arabidopsis, the gynoecium, the inner whorl of the flower, is the female reproductive part. Many tissues important for fertilization such as the stigma, style, transmitting tract, placenta, ovules, and septum, comprising the medial domain, arise from the carpel margin meristem. During gynoecium development, septum fusion occurs and tissues form continuously to prepare for a successful pollination and fertilization. During gynoecium development, cell wall modifications take place and one of the most important is the formation of the transmitting tract, having a great impact on reproductive competence because it facilitates pollen tube growth and movement through the ovary. In this study, using a combination of classical staining methods, fluorescent dyes and indirect immunolocalization we analyzed cell wall composition and modifications accompanying medial domain formation during gynoecium development. We detected coordinated changes in polysaccharide distribution through time, cell wall modifications preceding the formation of the transmitting tract, mucosubstances increase during transmitting tract formation, and a decrease of mannan distribution. Furthermore, we also detected changes in lipid distribution during septum fusion. Proper cell wall composition and modifications are important for postgenital fusion of the carpel (septum fusion) and transmitting tract formation, because these tissues affect plant reproductive competence.

Crecimiento indeterminado y determinado en Amaranthus hypochondriacus: ontogenia del meristemo apical y efecto sobre el peso de semilla

Abstract: espanolEl amaranto ( Amaranthus hypochondriacus L.) es importante por su contenido proteinico alto, pues el valor nutricional de su grano se debe, en parte, a la cantidad de proteinas superior a la de otros cereales. Los granos se forman en las inflorescen - cias y su arquitectura depende de que el crecimiento sea de - terminado o indeterminado. Mediante microscopia electroni - ca de barrido y tecnicas de clareo se obtuvieron imagenes de los cambios morfologicos del meristemo apical durante el ci - clo de vida de la planta. Ese tejido permanecio indiferenciado en el fenotipo indeterminado y la inflorescencia fue espigada, el meristemo apical detuvo su actividad con la formacion de cada flor terminal, lo que origino un desarrollo sincronizado. El desarrollo de la inflorescencia en el crecimiento determi - nado no presento traslape fenologico. Las ramificaciones de este ultimo fenotipo fueron mas cortas. Las semillas de plan - tas con crecimiento determinado fueron mas pesadas que las de crecimiento indeterminado. El estudio de la morfologia del meristemo apical podria ser base para el analisis de aspec - tos morfogeneticos del desarrollo, que a la vez, sean sustento para el mejoramiento genetico y manejo agronomico de A. hypochondriacus EnglishAmaranth ( Amaranthus hypochondriacus L.) is important for its high protein content, as the nutritional value of its grain is due partly to the amount of protein higher than that of other cereals. Grains form in the inflorescences and their architecture depend on whether growth is determinate or indeterminate. By means of scanning electron microscopy and thinning techniques, we obtained images of the morphological changes of the apical meristem during the life cycle of the plant. That tissue remained undifferentiated in the indeterminate phenotype and the inflorescence was spiked, the apical meristem stopped its activity with the formation of each terminal flower, originating a synchronized development. The development of the inflorescence in determinate growth did not present phenological overlap. The branches of this last phenotype were shorter. The seeds of plants with determinate growth were heavier than those of indeterminate growth. The study of apical meristem morphology could be the basis for the analysis of morphogenetic aspects of development, which at the same time are support for the genetic improvement and agronomic management of A. hypochondriacus .

Non-destructive Plant Morphometric and Color Analyses Using an Optoelectronic 3D Color Microscope

Abstract: Gene function discovery in plants, as other plant science quests, is aided by tools that image, document, and measure plant phenotypes. Tools that acquire images of plant organs and tissues at the microscopic level have evolved from qualitative documentation tools, to advanced tools where software-assisted analysis of images extracts quantitative information that allows statistical analyses. They are useful to perform morphometric studies that describe plant physical characteristics and quantify phenotypes, aiding gene function discovery. In parallel, non-destructive, versatile, robust, and user friendly technologies have also been developed for surface topography analysis and quality control in the industrial manufacture sector, such as optoelectronic three-dimensional (3D) color microscopes. These microscopes combine optical lenses, electronic image sensors, motorized stages, graphics engines, and user friendly software to allow the visualization and inspection of objects of diverse sizes and shapes from different angles. This allow the integration of different automatically obtained images along the Z axis of an object, into a single image with a large depth-of-field, or a 3D model in color. In this work, we explored the performance of an optoelectronic microscope to study plant morphological phenotypes and plant surfaces in different model species. Furthermore, as a "proof-of-concept," we included the phenotypic characterization (morphometric analyses at the organ level, color, and cell size measurements) of Arabidopsis mutant leaves. We found that the microscope tested is a suitable, practical, and fast tool to routinely and precisely analyze different plant organs and tissues, producing both high-quality, sharp color images and morphometric and color data in real time. It is fully compatible with live plant tissues (no sample preparation is required) and does not require special conditions, high maintenance, nor complex training. Therefore, though barely reported in plant scientific studies, optoelectronic microscopes should emerge as convenient and useful tools for phenotypic characterization in plant sciences.

An interaction map of transcription factors controlling gynoecium development in Arabidopsis

Abstract: Flowers are composed of different organs, whose identity is defined at the molecular by the combinatorial activity of transcription factors (TFs). MADS-box TFs interact forming complexes that have been schematized in the quartet model. The gynoecium is the female reproductive part in the flower, crucial for plant reproduction, and fruit and seed production. Once carpel identity is established, a gynoecium containing many tissues arises. Several TFs have been identified as regulators of gynoecium development, and some of these TFs form complexes. However, broad knowledge about the interactions among these TFs is still scarce. In this work, we used a systems biology approach to understand the formation of a complex reproductive unit as the gynoecium by mapping binary interactions between well-characterized TFs. We analyzed over 3500 combinations and detected more than 200 protein-protein interactions (PPIs), resulting in a process specific interaction map. Topological analyses suggest hidden functions and novel roles for many TFs. Furthermore, a relationship between TFs involved in auxin and cytokinin signaling pathways and other TFs was observed. We analyzed the network by combining PPI data, expression and genetic data, allowing us to dissect it into several dynamic spatio-temporal sub-networks related to gynoecium development subprocesses.