Duckweed roots are dispensable and are on a trajectory toward vestigiality

Duckweeds are morphologically simplified, free floating aquatic monocots comprising both rooted and rootless genera. This has led to the idea that roots in these species may be vestigial, but empirical evidence supporting this is lacking. Here we show that duckweed roots are no longer required for their ancestral role of nutrient uptake. Comparative analyses of nearly all rooted duckweed species revealed a highly reduced anatomy, with greater simplification in the more recently diverged genus Lemna. A series of root excision experiments demonstrated that roots are dispensable for normal growth in Spirodela polyrhiza and Lemna minor. Furthermore, ionomic analyses of fronds in these two species showed little difference in the elemental composition of plants in rooted versus root-excised samples. In comparison, another free-floating member of the Araceae, Pistia stratiotes, which colonized the aquatic environment independently of duckweeds, has retained a more complex root anatomy. Whilst Pistia roots were not absolutely required for growth, their removal inhibited plant growth and resulted in a broad change in the mineral profile of aerial tissues. Collectively, these observations suggest that duckweeds and Pistia may be different stages along a trajectory towards root vestigialisation Given this, along with the striking diversity of root phenotypes, culminating in total loss in the most derived species, we propose that duckweed roots are a powerful system with which to understand organ loss and vestigiality.

Plasticity and domestication of root anatomy in maize-teosinte derived population

Maize (Zea mays L.) underwent profound changes during domestication in root anatomy for environmental adaptation. However, the genetic mechanism of maize root anatomy domestication and plasticity remains unclear. In this study, a high-resolution mapping was performed for nine root anatomical traits using a maize-teosinte population (mexicana × Mo17) across three environments. Large genetic variations were detected for different root anatomical traits. The cortex area, stele area, aerenchyma area, xylem vessels number and cortical cell number had large variations across three environments, indicating high plasticity. Sixteen quantitative trait loci (QTL) were identified, including seven QTL with QTL × Environment interaction (EIQTL) for high plastic traits and nine QTL without QTL × Environment interaction (SQTL). Most of the root loci were consistent with shoot QTL depicting domestication signals. Combining transcriptome and genome-wide association study (GWAS) revealed that ZmPILS4 serve as a candidate gene underlying a major QTL of xylem traits. The near-isogenic lines (NILs) with lower expression of ZmPILS4 had 18-24% more IAA concentration in the root tip and 8-15% more xylem vessels. Significant domestication signal in promoter region suggested that ZmPILS4 was involved in maize domestication and adaptation. These results divulged the potential genetic basis of root anatomy plasticity and domestication.

Maxillary incisor internal root anatomy evaluated by cone-beam computed tomography in a population of the Autonomous City of Buenos Aires, Argentina

In the field of anthropology, discrete traits are considered as minimal epigenetic variations. However, they can elicit complications in endodontic therapy. Thorough understanding of root canal morphology is essential to achieving predictable results in endodontic practice, and may be attained by using cone-beam computed tomography (CBCT) scans. The aim of the present study was to research the internal root anatomy of maxillary central and lateral incisors in vivo and quantify its variation in a population of the Autonomous City of Buenos Aires, Argentina. A total 697 CBCT scans from a pre-existing database were observed, and the configuration type for each tooth was determined according to Vertucci’s classification. The data were described by absolute frequencies and percentages with 95% confidence intervals (CI). The CI was estimated by the Wilson Score method.Chi-square test (χ2 ) was used for comparing frequencies, with a 5% significance level. 238 CBCT scans met the inclusion criteria, resulting in 761 teeth assessed. Vertucci Type I configuration was observed in 760 teeth (99.9%) and the Type II was found in only one tooth (0.1%), in which the anatomy was compatible with dens in dente. When differences were analyzed according to sex, all the teeth in all women had Vertucci Type I configuration. In men, all maxillary central incisors were Vertucci Type I. Of 151 maxillary lateral incisors, 150 had Vertucci Type I configuration (99.3%) and 1 had Type II (0.7%). Conclusions: Maxillary incisor internal root anatomy prevalence was estimated from CBCT scans for the first time in an Argentine population. 99.9% of the sample presented Vertucci Type I configuration, and 0.1% had Vertucci Type II configuration. The clinical finding of maxillary incisors with anatomical complexity should be considered as a possibility in endodontic practice.

Intentional Replantation and 3d Obturation with Biodentine of a Resorbed Root in Young People: A Case Report

Referred patient 14 years old (in orthodontic treatment) for a suspected resorption on a 2.1 that was exposed to a trauma [1]. After an apical x ray, a cone beam was performed to have a complete diagnosis [2,3]. Almost the 80% of the root is resorbed, after achieving the parents’ consent to the treatment, was planned an intentional replantation [4] and a retrograde approach. In case like this the treatment’s goal is an intentional replantation to stop the root resorption, removing all the resorbing tissue and rebuild the root by biodentine’s use [5]. The tooth was replanted and splinted to the ortho appliances to allow a precise position of replantation. The final X ray control confirmed the correct rebuilding of the root anatomy. After two weeks the endodontic treatment was performed at all. After 6 months the patient has completed the ortho treatment and the X ray control revealed a good response, the biodentine‘s stability and no sign of tissue inflammation. Since the good preliminary results at six months of the intentional replantation with Biodentine root rebuilding, this treatment, in young patient, can be considered as a good option to the maintainability of the tooth till the adult age and to long lasting prosthetic treatments.

Root plasticity under abiotic stress

Abiotic stresses increasingly threaten existing ecological and agricultural systems across the globe. Plant roots perceive these stresses in the soil and adapt their architecture accordingly. This review provides insights into recent discoveries showing the importance of root system architecture and plasticity for the survival and development of plants under heat, cold, drought, salt, and flooding stress. In addition, we review the molecular regulation and hormonal pathways involved in controlling root system architecture plasticity, main root growth, branching and lateral root growth, root hair development and formation of adventitious roots. Several stresses affect root anatomy by causing aerenchyma formation, lignin and suberin deposition, and Casparian strip modulation. Roots can also actively grow towards favourable soil conditions and avoid environments detrimental to their development. Recent advances in understanding the cellular mechanisms behind these different root tropisms are discussed. Understanding root plasticity will be instrumental for the development of crops that are resilient in the face of abiotic stress.

Increased Mobility of the Atrial Septum in Aortic Root Dilation: An Observational Study on Transesophageal Echocardiography

Background: There is a growing interest in the relationship between atrial septal anatomy and cardioembolic stroke. Anecdotal reports suggest that the enlargement of the aortic root could interfere with atrial septal mobility (ASM). We sought to investigate the association between ASM and aortic root dilation.Methods and Findings: From all consecutive clinically requested transesophageal echocardiogram (TEE) studies performed during the study period in a single institution, we were able to review and evaluate the ASM and anteroposterior length, aortic root diameter, and the prevalence of atrial septal aneurysm (ASA) and of patent foramen ovale (PFO) in 336 studies. Additional variables, such as left ventricular ejection fraction, left atrial diameter, diastolic dysfunction, age, sex, weight, height, previous stroke, atrial fibrillation, and TEE indication, were extracted from patient medical records and echocardiographic clinical reports. In 336 patients, we found a mean ASM of 3.4 mm, ranging from 0 to 21 mm; 15% had ASA and 14% had PFO. There was a 1.0 mm increase in ASM for every 10-mm increase in aortic root diameter adjusted for age, sex, weight, height, ejection fraction, and left atrial size (B = 0.1; P = 0.04). Aortic diameter was not associated with a smaller septal length (B = 0.03; P = 0.7).Conclusion: An increased motion of the atrial septum can occur in association with aortic dilation. These findings deserve attention for the relevance of aortic root anatomy in future studies involving atrial septal characteristics and embolic stroke risk.