A Rhodnius prolixus catalytically inactive Calpain protease patterns the insect embryonic dorsal-ventral axis.

The calcium dependent Calpain proteases are modulatory enzymes with important roles in cell cycle control, development and immunity. In the fly model Drosophila melanogaster Calpain A cleaves Cactus/IkappaB and consequently modifies Toll signals during embryonic dorsal-ventral (DV) patterning. Here we explore the role of Calpains in the hemiptera Rhodnius prolixus, an intermediate germband insect where the Bone Morphogenetic Protein (BMP) instead of the Toll pathway plays a major role in DV patterning. Phylogenetic analysis of Calpains in species ranging from Isoptera to Diptera indicates an increase of Calpain sequences in the R. prolixus genome and other hemimetabolous species. One locus encoding each of the CalpC, CalpD and Calp7 families, and seven Calpain A/B loci are present in the R. prolixus genome. Several predicted R. prolixus Calpains display a unique architecture, such as loss of Calcium-binding EF-hand domains and loss of catalytic residues in the active site CysPc domain, yielding catalytically dead Calpains A/B. Knockdown for one of these inactive Calpains results in embryonic DV patterning defects, with expansion of ventral and lateral gene expression domains and consequent failure of germ band elongation. In conclusion, our results reveal that Calpains may exert a conserved function in insect DV patterning, despite the changing role of the Toll and BMP pathways in defining gene expression territories along the insect DV axis.

Gibberellin and miRNA156-targeted SlSBP genes synergistically regulate tomato floral meristem determinacy and ovary patterning.

Many developmental processes associated with fruit development occur at the floral meristem (FM). Age-regulated microRNA156 (miR156) and gibberellins (GAs) interact to control flowering time, but their interplay in subsequent stages of reproductive development is poorly understood. Here, in tomato (Solanum lycopersicum), we show that GA and miR156-targeted SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE (SPL or SBP) genes interact in the tomato FM and ovary patterning. High GA responses or overexpression of miR156 (156OE), which leads to low expression levels of miR156-silenced SBP genes, resulted in enlarged FMs, ovary indeterminacy and fruits with increased locule number. Conversely, low GA responses reduced indeterminacy and locule number, and overexpression of a S. lycopersicum (Sl)SBP15 allele that is miR156 resistant (rSBP15) reduced FM size and locule number. GA responses were partially required for the defects observed in 156OE and rSBP15 fruits. Transcriptome analysis and genetic interactions revealed shared and divergent functions of miR156-targeted SlSBP genes, PROCERA/DELLA and the classical WUSCHEL/CLAVATA pathway, which has been previously associated with meristem size and determinacy. Our findings reveal that the miR156/SlSBP/GA regulatory module is deployed differently depending on developmental stage and create novel opportunities to fine-tune aspects of fruit development that have been important for tomato domestication.

A pro-BMP function exerted by Rhodnius prolixus short gastrulation reveals great diversity in the role of BMP modulators during embryonic patterning.

Dorsal-ventral (DV) patterning is regulated by the bone morphogenetic pathway (BMP) in Bilateria. In insect DV patterning, the Toll pathway also plays a role, in addition to BMPs. Variations in the relative importance of each pathway for DV patterning have been reported using single species of coleopteran, hymenopteran, hemipteran and orthopteran insects. To investigate if the molecular control of DV patterning is conserved inside an insect order, the emergent model hemiptera species Rhodnius prolixus was studied. We found that R. prolixus BMP pathway controls the entire DV axis, with a broader effect respective to Toll, as shown for the hemiptera Oncopeltus fasciatus. Different from O. fasciatus, the unique R. prolixus short gastrulation (sog) and the twisted gastrulation (tsg) orthologues do not antagonize, but rather favour embryonic BMP signalling. Our results reinforce the hypothesis that hemiptera rely preferentially on BMPs for DV patterning but that, surprisingly, in R. prolixus Sog and Tsg proteins exert only a positive role to establish a dorsal-to-ventral BMP gradient. Since sog has been reported to be lost from orthopteran and hymenopteran genomes, our results indicate that Sog's role to modify BMP activity varies greatly in different insect species.

Integration failure of regenerated limb tissue is associated with incongruencies in positional information in the Mexican axolotl.

Introduction: Little is known about how the newly regenerated limb tissues in the Mexican axolotl seamlessly integrate with the remaining stump tissues to form a functional structure, and why this doesn't occur in some regenerative scenarios. In this study, we evaluate the phenomenological and transcriptional characteristics associated with integration failure in ectopic limb structures generated by treating anterior-located ectopic blastemas with Retinoic Acid (RA) and focusing on the "bulbus mass" tissue that forms between the ectopic limb and the host site. We additionally test the hypothesis that the posterior portion of the limb base contains anterior positional identities. Methods: The positional identity of the bulbus mass was evaluated by assaying regenerative competency, the ability to induce new pattern in the Accessory Limb Model (ALM) assay, and by using qRTPCR to quantify the relative expression of patterning genes as the bulbus mass deintegrates from the host site. We additionally use the ALM and qRTPCR to analyze the distribution of anterior and posterior positional identities along the proximal/distal limb axis of uninjured and regenerating limbs. Results: The bulbus mass regenerates limb structures with decreased complexity when amputated and is able to induce complex ectopic limb structure only when grafted into posterior-located ALMs. Expressional analysis shows significant differences in FGF8, BMP2, TBX5, Chrdl1, HoxA9, and HoxA11 expression between the bulbus mass and the host site when deintegration is occuring. Grafts of posterior skin from the distal limb regions into posterior ALMs at the base of the limb induce ectopic limb structures. Proximally-located blastemas express significantly less HoxA13 and Ptch1, and significantly more Alx4 and Grem1 than distally located blastemas. Discussion: These findings show that the bulbus mass has an anterior-limb identity and that the expression of limb patterning genes is mismatched between the bulbus mass and the host limb. Our findings additionally show that anterior positional information is more abundant at the limb base, and that anterior patterning genes are more abundantly expressed in proximally located blastemas compared to blastemas in the more distal regions of the limb. These experiments provide valuable insight into the underlying causes of integration failure and further map the distribution of positional identities in the mature limb.

Vestigial-dependent induction contributes to robust patterning but is not essential for wing-fate recruitment in Drosophila.

Cell recruitment is a process by which a differentiated cell induces neighboring cells to adopt its same cell fate. In Drosophila, cells expressing the protein encoded by the wing selector gene, vestigial (vg), drive a feed-forward recruitment signal that expands the Vg pattern as a wave front. However, previous studies on Vg pattern formation do not reveal these dynamics. Here, we use live imaging to show that multiple cells at the periphery of the wing disc simultaneously activate a fluorescent reporter of the recruitment signal, suggesting that cells may be recruited without the need for their contact neighbors be recruited in advance. In support of this observation, when Vg expression is inhibited either at the dorsal-ventral boundary or away from it, the activation of the recruitment signal still occurs at a distance, suggesting that Vg expression is not absolutely required to send or propagate the recruitment signal. However, the strength and extent of the recruitment signal is clearly compromised. We conclude that a feed-forward, contact-dependent cell recruitment process is not essential for Vg patterning, but it is necessary for robustness. Overall, our findings reveal a previously unidentified role of cell recruitment as a robustness-conferring cell differentiation mechanism.

The role of Wnt signaling in Xenopus neural induction.

Development of the central nervous system in amphibians has called attention from scientists for over a century. Interested in the matter of embryonic inductions, Hans Spemann and Hilde Mangold found out that the dorsal blastopore lip of the salamander's embryo has organizer properties. Such an ectopic graft could induce structures in the host embryo, including a neural tube overlying the notochord of a perfect secondary body axis. A couple of decades later, the frog Xenopus laevis emerged as an excellent embryological experimental model and seminal concepts involving embryonic inductions began to be revealed. The so-called primary induction is, in fact, a composition of signaling and inductive events that are triggered as soon as fertilization takes place. In this regard, since early 1990s an intricate network of signaling pathways has been built. The Wnt pathway, which began to be uncovered in cancer biology studies, is crucial during the establishment of two signaling centers in Xenopus embryogenesis: Nieuwkoop center and the blastula chordin noggin expression center (BCNE). Here we will discuss the historical events that led to the discovery of those centers, as well as the molecular mechanisms by which they operate. This chapter highlights the cooperation of both signaling centers with potential to be further explored in the future. We aim to address the essential morphological transformation during gastrulation and neurulation as well as the role of Wnt signaling in patterning the organizer and the neural plate.

An analysis of lateralized neural crest marker expression across development in the Mexican tetra, Astyanax mexicanus.

The biological basis of lateralized cranial aberrations can be rooted in early asymmetric patterning of developmental tissues. However, precisely how development impacts natural cranial asymmetries remains incompletely understood. Here, we examined embryonic patterning of the cranial neural crest at two phases of embryonic development in a natural animal system with two morphotypes: cave-dwelling and surface-dwelling fish. Surface fish are highly symmetric with respect to cranial form at adulthood, however adult cavefish harbor diverse cranial asymmetries. To examine if lateralized aberrations of the developing neural crest underpin these asymmetries, we used an automated technique to quantify the area and expression level of cranial neural crest markers on the left and right sides of the embryonic head. We examined the expression of marker genes encoding both structural proteins and transcription factors at two key stages of development: 36 hpf (∼mid-migration of the neural crest) and 72 hpf (∼early differentiation of neural crest derivatives). Interestingly, our results revealed asymmetric biases at both phases of development in both morphotypes, however consistent lateral biases were less common in surface fish as development progressed. Additionally, this work provides the information on neural crest development, based on whole-mount expression patterns of 19 genes, between stage-matched cave and surface morphs. Further, this study revealed 'asymmetric' noise as a likely normative component of early neural crest development in natural Astyanax fish. Mature cranial asymmetries in cave morphs may arise from persistence of asymmetric processes during development, or as a function of asymmetric processes occurring later in the life history.

An additive repression mechanism sets the anterior limits of anterior pair-rule stripes 1.

Segments are repeated anatomical units forming the body of insects. In Drosophila, the specification of the body takes place during the blastoderm through the segmentation cascade. Pair-rule genes such as hairy (h), even-skipped (eve), runt (run), and fushi-tarazu (ftz) are of the intermediate level of the cascade and each pair-rule gene is expressed in seven transversal stripes along the antero-posterior axis of the embryo. Stripes are formed by independent cis-regulatory modules (CRMs) under the regulation of transcription factors of maternal source and of gap proteins of the first level of the cascade. The initial blastoderm of Drosophila is a syncytium and it also coincides with the mid-blastula transition when thousands of zygotic genes are transcribed and their products are able to diffuse in the cytoplasm. Thus, we anticipated a complex regulation of the CRMs of the pair-rule stripes. The CRMs of h 1, eve 1, run 1, ftz 1 are able to be activated by bicoid (bcd) throughout the anterior blastoderm and several lines of evidence indicate that they are repressed by the anterior gap genes slp1 (sloppy-paired 1), tll (tailless) and hkb (huckebein). The modest activity of these repressors led to the premise of a combinatorial mechanism regulating the expression of the CRMs of h 1, eve 1, run 1, ftz 1 in more anterior regions of the embryo. We tested this possibility by progressively removing the repression activities of slp1, tll and hkb. In doing so, we were able to expose a mechanism of additive repression limiting the anterior borders of stripes 1. Stripes 1 respond depending on their distance from the anterior end and repressors operating at different levels.

Concerted variation in melanogenesis genes underlies emergent patterning of plumage in capuchino seedeaters.

Coloration traits are central to animal communication; they often govern mate choice, promote reproductive isolation and catalyse speciation. Specific genetic changes can cause variation in coloration, yet far less is known about how overall coloration patterns-which involve combinations of multiple colour patches across the body-can arise and are genomically controlled. We performed genome-wide association analyses to link genomic changes to variation in melanin (eumelanin and pheomelanin) concentration in feathers from different body parts in the capuchino seedeaters, an avian radiation with diverse colour patterns despite remarkably low genetic differentiation across species. Cross-species colour variation in each plumage patch is associated with unique combinations of variants at a few genomic regions, which include mostly non-coding (presumably regulatory) areas close to known pigmentation genes. Genotype-phenotype associations can vary depending on patch colour and are stronger for eumelanin pigmentation, suggesting eumelanin production is tightly regulated. Although some genes are involved in colour variation in multiple patches, in some cases, the SNPs associated with colour changes in different patches segregate spatially. These results suggest that coloration patterning in capuchinos is generated by the modular combination of variants that regulate multiple melanogenesis genes, a mechanism that may have promoted this rapid radiation.

Cellular and molecular bases of lateral root initiation and morphogenesis.

Lateral root development is essential for the establishment of the plant root system. Lateral root initiation is a multistep process that impacts early primordium morphogenesis and is linked to the formation of a morphogenetic field of pericycle founder cells. Gradual recruitment of founder cells builds this morphogenetic field in an auxin-dependent manner. The complex process of lateral root primordium morphogenesis includes several subprocesses, which are presented in this review. The underlying cellular and molecular mechanisms of these subprocesses are examined.

Root Patterning: Tuning SHORT ROOT Function Creates Diversity in Form.

Roots have a fundamental role in plant growth and adaptation to different environments. Diversity in root morphology and architecture enables plants to acquire water and nutrients in contrasting substrate conditions, resist biotic and abiotic stress, and develop symbiotic associations. At its most fundamental level, morphology is determined by discrete changes in tissue patterning. Differences in the number and arrangement of the cell layers in the root can change tissue structure, as well as root length and girth, affecting important productivity traits. Therefore, understanding the molecular mechanisms controlling variation in developmental patterning is an important goal in biology. The ground tissue (GT) system is an ideal model to study the genetic basis of morphological diversity because it displays great interspecific variability in cell layer number. In addition, the genetic circuit controlling GT patterning in Arabidopsis thaliana has been well described, although little is known about species with more complex root anatomies. In this review, we will describe the Arabidopsis model for root radial patterning and present recent progress in elucidating the genetic circuitry controlling GT patterning in monocots and the legume Medicago truncatula (Mt), species that develop roots with more complex anatomies and multilayered cortex.

Conditioning of hiPSC-derived cardiomyocytes using surface topography obtained with high throughput technology.

Surface functionalization of polymers aims to introduce novel properties that favor bioactive responses. We have investigated the possibility of surface functionalization of polyethylene terephthalate (PET) sheets by the combination of laser ablation with hot embossing and the application of such techniques in the field of stem cell research. We investigated the response of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) to topography in the low micrometer range. HiPSC-CMs are expected to offer new therapeutic tools for myocardial replacement or regeneration after an infarct or other causes of cardiac tissue loss. However, hiPSC-CMs are phenotypically immature compared to myocytes in the adult myocardium, hampering their clinical application. We aimed to develop and test a high-throughput technique for surface structuring that would improve hiPSC-CMs structural maturation. We used laser ablation with a ps-laser source in combination with nanoimprint lithography to fabricate large areas of homogeneous micron- to submicron line-like pattern with a spatial period of 3 µm on the PET surface. We evaluated cell morphology, alignment, sarcomeric myofibrils assembly, and calcium transients to evaluate phenotypic changes associated with culturing hiPSC-CMs on functionalized PET. Surface functionalization through hot embossing was able to generate, at low cost, low micrometer features on the PET surface that influenced the hiPSC-CMs phenotype, suggesting improved structural and functional maturation. This technique may be relevant for high-throughput technologies that require conditioning of hiPSC-CMs and may be useful for the production of these cells for drug screening and disease modeling applications with lower costs.

Morphospace analysis leads to an evo-devo model of digit patterning.

Biological forms occupy a constrained portion of theoretical morphospaces. Developmental models accounting for empirical morphospaces are necessary to achieve a better understanding of this phenomenon. We analyzed the phalangeal formulas (PFs) in lizards and relatives' hands by comparing them with a set of simulated PFs that compose a theoretical morphospace. We detected that: (1) the empirical morphospace is severely limited in size, (2) the PFs comply with two properties of phalangeal count per digit, namely the ordering rule (DI ≤ DII ≤ DIII ≤ DIV ≥ DV), and the contiguity relationship (neighbor digits differ on average in one phalanx), (3) the totality of the PFs can be categorized into four categories of hands aligned along a feasibility gradient. We also reconstructed the evolution of PFs and found a stepwise trajectory from the plesiomorphic PF towards reduced conditions. Finally, we propose a developmental model as the generative mechanism behind the PFs. It is consistent with the bulk of evidence managed and involves an ordered digit primordia initialization timed with periodic signals of joint formation coming from digit tips. Our approach is also useful to address the study of other meristic sequences in nature such as dental, floral, and branchial formulas.

A dynamic cell recruitment process drives growth of the Drosophila wing by overscaling the vestigial expression pattern.

Organs mainly attain their size by cell growth and proliferation, but sometimes also grow through recruitment of undifferentiated cells. Here we investigate the participation of cell recruitment in establishing the pattern of Vestigial (Vg), the product of the wing selector gene in Drosophila. We find that the Vg pattern overscales along the dorsal-ventral (DV) axis of the wing imaginal disc, i.e., it expands faster than the DV length of the pouch. The overscaling of the Vg pattern cannot be explained by differential proliferation, apoptosis, or oriented-cell divisions, but can be recapitulated by a mathematical model that explicitly considers cell recruitment. When impairing cell recruitment genetically, we find that the Vg pattern almost perfectly scales and adult wings are approximately 20% smaller. Conversely, impairing cell proliferation results in very small wings, suggesting that cell recruitment and cell proliferation additively contribute to organ growth in this system. Furthermore, using fluorescent reporter tools, we provide direct evidence that cell recruitment is initiated between early and mid third-instar larval development. Altogether, our work quantitatively shows when, how, and by how much cell recruitment shapes the Vg pattern and drives growth of the Drosophila wing.

The Lived Experiences of Folklore Healing Practices as a Health Patterning Modality.

Purpose: The purpose of the study is to understand the meaning of folklore as a health patterning modality and to uncover its unique characteristics in the life-health process. Design: Hermeneutic phenomenological. Method: Max van Manen's methodology was used for this study. The sample was selected from the Afro-Caribbean American community in the United States. The criterion for selection was that participants used folklore healing practices for health and well-being on an ongoing basis. In-depth interviews were done. Purposive sampling with networking was done based on whether the participants used folk healing on a regular basis. Themes of the meaning of folklore healing practices were identified from participants' verbatim data. Findings: The meaning of folklore healing practices was interpreted as phenomena with six interconnected essential themes. Additionally, Barrett's nursing theory of power as knowing participation in change was used to reflect and understand the findings from a nursing perspective. Conclusion: The research findings have implications for nursing science, and the knowledge gleaned from the study may be applied to nursing practice.

Consumption of a high-fat diet does not potentiate the deleterious effects on lipid and protein levels and body development in rats subjected to maternal protein restriction.

Maternal undernutrition may cause injuries in several organs of the offspring, as well as lead to diseases in adulthood. Obesity and/or the consumption of a high-fat diet may also induce metabolic and cardiorespiratory diseases. We hypothesized that the consumption of a post-weaning high-fat diet would potentiate the deleterious effects of maternal protein undernutrition. This study evaluated the effects of the association of a low-protein diet during gestation and lactation with a post-weaning high-fat diet on the biochemical and ventilatory parameters of rats. Male Wistar rats from mothers who received a low-protein (9% of protein) or normoprotein diet during pregnancy and lactation received a high-fat (32% of total kilocalories from lipids) or a normal fat diet after weaning. Mass gain and somatic growth of the offspring were monitored. Also examined were biochemical chemical parameters and respiratory frequency, tidal volume (volume of air displaced in each normal respiratory cycle when extra effort is not applied), and pulmonary ventilation. Offspring from undernourished mothers presented lower birth weight (P = .0225), which remained until the end of lactation (P < .01). The rats that consumed high-fat diet and had been submitted to maternal undernutrition presented higher tidal volume when compared to the ones that consumed control diet at the 21st day of life (P Ë‚ .05). At 30 and 90 days, no further ventilatory changes were observed. Our data show that the consumption of a high-fat diet post-weaning did not seem to potentiate the changes induced by maternal undernutrition.

El ideal de cuerpo delgado y la formación del sujeto neoliberal: un estudio de caso / O ideal do corpo magro e a formação do sujeito neoliberal: um estudo de caso / The thin body ideal and the constitution of the neoliberal subject: a case study

El objetivo de este artículo es mostrar mediante un estudio de caso único, cómo la discrepancia entre la imagen corporal del ideal delgado y la real puede estimular los procesos de formación del sujeto neoliberal. El instrumento de recogida de información fue la entrevista cualitativa, abierta y semiestructurada. Los resultados muestran cómo la imagen corporal del ideal delgado puede funcionar como una tecnología de poder, al exhibir un cuerpo normalizado y homogéneo que estimula los procesos reflexivos críticos sobre uno mismo, procesos que pueden abocar en prácticas de transformación del propio cuerpo, contribuyendo a la construcción de sujetos sensibles al impulso neoliberal. Finalmente, aportamos algunas implicaciones pedagógicas para el desarrollo de tecnologías del yo liberadoras orientadas al autoconocimiento y al aumento de la consciencia crítica.

O objetivo deste artigo é mostrar, através de um único estudo de caso, como a discrepância entre a imagem corporal do magro ideal e o real pode estimular os processos de formação do sujeito neoliberal. O instrumento de coleta de informações foi a entrevista qualitativa, aberta e semi-estruturada. Os resultados mostram como a imagem corporal do ideal magro pode funcionar como uma tecnologia de potência, exibindo um corpo ideal normalizado e homogêneo que estimula processos reflexivos críticos sobre si mesmo, processos que podem levar a práticas de transformação do próprio corpo, contribuindo para a construção do corpo, contribuído para a construção de sujeitos sensíveis ao impulso neoliberal. Por fim, fornecemos algumas implicações pedagógicas para o desenvolvimento de tecnologias libertadoras de si voltadas para o autoconhecimento e o aumento da consciência crítica.

As a single case study, this paper shows how the discrepancy between the thin-ideal body image and the real body can drive processes that form the neoliberal subject. Data were collected through qualitative, open and semi-structured interviews. The results show how the thin-ideal body image can function as a power technology by exhibiting a normalized and homogeneous ideal body that stimulates critical reflective processes about oneself, which can lead to practices of transformation of the body itself, contributing to form subjects that are receptive to the neoliberal impulse. Finally, we point out some pedagogical implications for the development of liberating technologies of the self, aimed at self-knowledge and increasing critical awareness.

Bimodal Patterning Discrimination in Harnessed Honey Bees.

In natural environments, stimuli and events learned by animals usually occur in a combination of more than one sensory modality. An important problem in experimental psychology has been thus to understand how organisms learn about multimodal compounds and how they discriminate this compounds from their unimodal constituents. Here we tested the ability of honey bees to learn bimodal patterning discriminations in which a visual-olfactory compound (AB) should be differentiated from its visual (A) and olfactory (B) elements. We found that harnessed bees trained in classical conditioning of the proboscis extension reflex (PER) are able to solve bimodal positive and negative patterning (NP) tasks. In positive patterning (PP), bees learned to respond significantly more to a bimodal reinforced compound (AB+) than to non-reinforced presentations of single visual (A-) or olfactory (B-) elements. In NP, bees learned to suppress their responses to a non-reinforced compound (AB-) and increase their responses to reinforced presentations of visual (A+) or olfactory (B+) elements alone. We compared the effect of two different inter-trial intervals (ITI) in our conditioning approaches. Whereas an ITI of 8 min allowed solving both PP and NP, only PP could be solved with a shorter ITI of 3 min. In all successful cases of bimodal PP and NP, bees were still able to discriminate between reinforced and non-reinforced stimuli in memory tests performed one hour after conditioning. The analysis of individual performances in PP and NP revealed that different learning strategies emerged in distinct individuals. Both in PP and NP, high levels of generalization were found between elements and compound at the individual level, suggesting a similar difficulty for bees to solve these bimodal patterning tasks. We discuss our results in light of elemental and configural learning theories that may support the strategies adopted by honey bees to solve bimodal PP or NP discriminations.

Dynamical Patterning Modules, Biogeneric Materials, and the Evolution of Multicellular Plants.

Comparative analyses of developmental processes across a broad spectrum of organisms are required to fully understand the mechanisms responsible for the major evolutionary transitions among eukaryotic photosynthetic lineages (defined here as the polyphyletic algae and the monophyletic land plants). The concepts of dynamical patterning modules (DPMs) and biogeneric materials provide a framework for studying developmental processes in the context of such comparative analyses. In the context of multicellularity, DPMs are defined as sets of conserved gene products and molecular networks, in conjunction with the physical morphogenetic and patterning processes they mobilize. A biogeneric material is defined as mesoscale matter with predictable morphogenetic capabilities that arise from complex cellular conglomerates. Using these concepts, we outline some of the main events and transitions in plant evolution, and describe the DPMs and biogeneric properties associated with and responsible for these transitions. We identify four primary DPMs that played critical roles in the evolution of multicellularity (i.e., the DPMs responsible for cell-to-cell adhesion, identifying the future cell wall, cell differentiation, and cell polarity). Three important conclusions emerge from a broad phyletic comparison: (1) DPMs have been achieved in different ways, even within the same clade (e.g., phycoplastic cell division in the Chlorophyta and phragmoplastic cell division in the Streptophyta), (2) DPMs had their origins in the co-option of molecular species present in the unicellular ancestors of multicellular plants, and (3) symplastic transport mediated by intercellular connections, particularly plasmodesmata, was critical for the evolution of complex multicellularity in plants.

Arabidopsis thaliana homeodomain-leucine zipper type I transcription factors contribute to control leaf venation patterning.

Venation patterning is a taxonomic attribute for classification of plants and it also plays a role in the interaction of plants with the environment. Despite its importance, the molecular physiology controlling this aspect of plant development is still poorly understood. Auxin plays a central role modulating the final vein network and patterning. This addendum discusses recent findings on the role of homeodomain-leucine zipper (HD-Zip) transcription factors on the regulation of leaf venation patterning. Moreno-Piovano et al. reported that ectopic expression of a sunflower HD-Zip I gene, HaHB4, increased the asymmetry of leaf venation. Even more, this work showed that auxin transport in the leaf through LAX carriers controls venation patterning. Here, we provide evidence indicating that some Arabidopsis thaliana HD-Zip I genes play a role in the determination of the final leaf venation patterning. We propose that these genes contribute to regulate vein patterning, likely controlling auxin homeostasis.