Monique Welten

• Dr.
• Editor at Naturalis Biodiversity Center

The dry one-seeded fruits (cypselae) of the Asteraceae are often crowned with a pappus, an appendage of hairs or scales that assists in dispersal. It is generally assumed, but little investigated, that the pappus represents the outer floral whorl where the sepals are usually located. We analysed pappus–sepal homology in dandelions using micromorpho...

We resolve debate over the evolution of vertebrate hypermineralized tissues through analyses of matrix protein-encoding secretory calcium-binding phosphoprotein (SCPP) genes and phylogenetic inference of hypermineralized tissues. Among these genes, AMBN and ENAM are found in both sarcopterygians and actinopterygians, while AMEL and SCPP5 are found...

Background: Variation in shape and size of many floral organs is related to pollinators. Evolution of such organs is driven by duplication and modification of MADS-box and MYB transcription factors. We applied a combination of micro-morphological (SEM and micro 3D-CT scanning) and molecular techniques (transcriptome and RT-PCR analysis) to underst...

Background: Lantern plants from the genus Ceropegia (Apocynaceae-Asclepiadoideae) have radially symmetric pitfall flowers that are an outstanding example of functional floral complexity with high synorganization of specialized organs. The evolutionary origin and development of these complex flowers is unclear, and the genetic background of floral o...

In classical theory, teeth of vertebrate dentitions evolved from co-option of external skin denticles into the oral cavity. This hypothesis predicts that ordered tooth arrangement and regulated replacement in the oral dentition were also derived from skin denticles. The fossil batoid ray Schizorhiza stromeri (Chondrichthyes; Cretaceous) provides a...

A well-known characteristic of chondrichthyans (e.g. sharks, rays) is their covering of external skin denticles (placoid scales), but less well understood is the wide morphological diversity that these skin denticles can show. Some of the more unusual of these are the tooth-like structures associated with the elongate cartilaginous rostrum ‘saw’ in...

Shark and ray (elasmobranch) dentitions are well known for their multiple generations of teeth, with isolated teeth being common in the fossil record. However, how the diverse dentitions characteristic of elasmobranchs form is still poorly understood. Data on the development and maintenance of the dental patterning in this major vertebrate group wi...

The precise control of gene expression is critical in embryonic development. Quantitative assays, such as microarrays and RNA sequencing, provide gene expression levels for a large number of genes, but do not contain spatial information. In contrast, in situ methods, such as in situ hybridisation and immunohistochemistry, provide spatial resolution...

Specification of digit number and identity is central to digit pattern in vertebrate limbs. The classical talpid(3) chicken mutant has many unpatterned digits together with defects in other regions, depending on hedgehog (Hh) signalling, and exhibits embryonic lethality. The talpid(3) chicken has a mutation in KIAA0586, which encodes a centrosomal...

Sonic hedgehog (Shh) signalling controls integrated specification of digit pattern and growth in the chick wing but downstream gene networks remain to be unravelled. We analysed 3D expression patterns of genes encoding cell cycle regulators using Optical Projection Tomography. Hierarchical clustering of spatial matrices of gene expression revealed...

showing a 3D view of unique spatial domain clusters representing regions fated to form digits in stage 21 wing bud. Digit 2: yellow, digit 3: pink, digit 4: white. (MPG)

showing a 3D view of unique spatial domain clusters representing regions fated to form digits in stage 24 wing bud. Digit 2: yellow, digit 3: pink, digit 4: white. (MPG)

showing a 3D view of unique spatial domain clusters representing regions fated to form digits in stage 27 wing bud. Digit 2: yellow, digit 3: pink, digit 4: white. (MPG)

Hoxd13, Tbx2, Tbx3, Sall1 and Sall3 genes are candidates for encoding antero-posterior positional values in the developing chick wing and specifying digit identity. In order to build up a detailed profile of gene expression patterns in cell lineages that give rise to each of the digits over time, we compared 3 dimensional (3D) expression patterns o...

Eggs containing live Japanese quail embryos were imaged using micro-magnetic resonance imaging (μMRI) at 24-h intervals from Day 0 to 8, the period during which the main body axis is being laid down and organogenesis is taking place. Considerable detail of non-embryonic structures such as the latebra was revealed at early stages but the embryo coul...

Supplementary Data.

We introduce a new method for the analysis of heterochrony in developmental biology. Our method is based on methods used in data mining and intelligent data analysis and applied in, e.g., shopping basket analysis, alarm network analysis and click stream analysis. We have transferred, so called, frequent episode mining to operate in the analysis of...

Sonic hedgehog (Shh) signalling by the polarizing region at the posterior margin of the chick wing bud is pivotal in patterning the digits but apart from a few key downstream genes, such as Hoxd13, which is expressed in the posterior region of the wing that gives rise to the digits, the genes that mediate the response to Shh signalling are not know...

During the upsurge of the introduced predatory Nile perch in Lake Victoria in the 1980s, the zooplanktivorous 'Haplochromis (Yssichromis) pyrrhocephalus' nearly vanished. The species recovered coincident with the intense fishing of Nile perch in the 1990s, when water clarity and dissolved oxygen levels had decreased dramatically due to increased eu...

The construction of gene regulatory models from microarray time-series data has received much attention. Here we propose a method that extends standard correlation networks to incorporate explicit time-slices. The method is applied to a time-series dataset of a study on gene expression in the developmental phase of zebrafish. Results show that the...

We present a method and protocol for fluorescent in situ hybridization (FISH) in zebrafish embryos to enable three-dimensional imaging of patterns of gene expression using confocal laser scanning microscopy. We describe the development of our protocol and the processing workflow of the three-dimensional images from the confocal microscope. We refer...

The zebrafish (Danio rerio) is an important model in evolutionary developmental biology, and its study is being revolutionized by the zebrafish genome project. Sequencing is at an advanced stage, but annotation is largely the result of in silico analyses. We have performed genomic annotation, comparative genomics, and transcriptional analysis using...

The bird wing is of special interest to students of homology and avian evolution. Fossil and developmental data give conflicting indications of digit homology if a pentadactyl "archetype" is assumed. Morphological signs of a vestigial digit I are seen in bird embryos, but no digit-like structure develops in wild-type embryos. To examine the develop...

A total of 15 taxa of marine benthic algae from GuineaBissau are identified, namely 3 in the Chlorophyceae, 5 in the Phaeophyceae and 7 in the Rhodophyceae. All of these are new records for GuineaBissau.

In developmental biology, the expression of genes is studied to understand development, phenotypes and to construct models to understand disease. In this thesis, we explore and validate biological as well as computerized tools, to address research questions in developmental biology. Based on these techniques, we developed a workflow to generate a l...