Ontogenic study of the brachiopod Dicoelosia by geometric morphometrics and morphing techniques

The distinctive brachiopod Dicoelosia King 1850 is characterized by a strongly bilobed outline. To date, studies have concentrated on its functional morphology, taxonomy and evolution; little attention has been paid to its ontogeny. Here, we map population variation by principal component analysis for over 80 specimens distributed across five species of Dicoelosia. Using geometric morphometrics with landmarks for some 40 specimens, the ontogenic trends in D. sp. nov. are compared with those of Dicoelosia biloba. In addition, the ontogenic pathway in D. sp. nov. is investigated by morphing with control points, a new technique introduced here to palaeontology. Combining the results above, the ontogeny of the key character of the genus, emargination, is modelled. Within single populations, taxa may develop from broad weakly emarginate forms into those that are elongate and deeply emarginate. As the identification of the genus and its species depends on external morphological characters, the definition of ontogenetic trends in each species is essential for taxonomic discrimination. Substantial population variation exists in many of its species; however, the morphing technique provides a method of simulation, predicting the full range of ontogenetic variation in given populations.     

A molecular systematic investigation of the Acrochaetiales (Florideophycidae,Rhodophyta) and related taxa based on nuclear small-subunit ribosomal DNA sequence data

Small-subunit ribosomal DNA (SSU) sequences for 14 members of the rhodophyte order Acrochaetiales were used to generate phylogenetic trees to determine whether the Acrochaetiales is monophyletic and to assess the relationships of acrochaetioid algae to closely related taxa. Within the Acrochaetiales, two strongly supported groups are recognized: one group that includes, in addition to three other species, the type species of the genera Acrochaetium, Audouinella and Rhodochorton; and a second group that includes an unequivocal representative of Colaconema and nine additional species. The relationships of these groups with the Batrachospermales, Palmariales and Nemaliales were not resolved and the possibility that the Acrochaetiales is polyphyletic was not eliminated. Resolution of relationships for species within these groups was strong in only a few cases, with many of the phylogenetic issues at this level remaining equivocal. Our results do not position Camontagnea in the Acrochaetiales, as has recently been suggested, but strongly ally this genus to the family Rhodothamniellaceae of the Palmariales. The phylogenetic position of Rhododraparnaldia, an alga intermediate between the Acrochaetiales and Batrachospermales, remains unresolved. These molecular results provide a foundation for assessing the taxonomic significance of phenotypic characters (e.g. anatomy, life histories, morphology, phycoerythrin type and plastid details) variously considered taxonomically significant in the Acrochaetiales.     

Some Hormonal Effects on Liver Fat Accumulation Owing to an Amino Acid Imbalance

Rats fed a low protein diet containing choline in which casein supplemented with sulfur-containing amino acids is the protein source develop moderately fatty livers. Effects of some hormones on this type of fatty liver were investigated. The accumulation of fat in the liver was alleviated by injection of thyroxine. Adrenalectomy also prevented the induction of fatty liver but fat accumulated excessively in adrenalectomized rats by the injection with cortisol.     

Common Variation Neighbouring Micro-RNA 22 Is Associated with Increased Left Ventricular Mass

Aims

Previous genome-wide linkage analysis has suggested that chromosomal region 17p13.3 may harbour genes influencing left ventricular mass (LVM) in man. To date, the genetic factors accounting for LVM variability remain largely unknown but a non-coding RNA gene within this region, micro-RNA 22 (miR-22), has been implicated in cardiac hypertrophy and heart failure in animal models. We thus investigated the relationship between common genetic polymorphisms surrounding miR-22 and left ventricular mass in a family-based association study.

Methods and Results

We studied a cohort of 255 families comprising 1,425 individuals ascertained via a hypertensive proband. Ten single nucleotide polymorphisms which together tagged common genetic variation surrounding the miR-22 gene were genotyped. There was evidence of association between the rs7223247 polymorphism, which lies within the 3′UTR of a gene of unknown function, TLCD2, immediately downstream from miR-22, and left ventricular mass determined by Sokolow-Lyon voltage (Bonferroni corrected p-value = 0.038). The T allele at rs7223247 was associated with an 0.272 standard deviation higher Sokolow-Lyon voltage. Genotype was responsible for ∼1% of the population variability in LVM.

Conclusions

Genotype at the rs7223247 polymorphism affects left ventricular mass determined by Sokolow-Lyon voltage. The neighbouring genes miR-22 and TLCD2 are strong candidates to account for this observation.     

Direct analysis of pollen fitness by flow cytometry: implications for pollen response to stress

Sexual reproduction in flowering plants depends on the fitness of the male gametophyte during fertilization. Because pollen development is highly sensitive to hot and cold temperature extremes, reliable methods to evaluate pollen viability are important for research into improving reproductive heat stress (HS) tolerance. Here, we describe an approach to rapidly evaluate pollen viability using a reactive oxygen species (ROS) probe dichlorodihydrofluorescein diacetate (i.e. H₂DCFDA‐staining) coupled with flow cytometry. In using flow cytometry to analyze mature pollen harvested from Arabidopsis and tomato flowers, we discovered that pollen distributed bimodally into ‘low‐ROS’ and ‘high‐ROS’ subpopulations. Pollen germination assays following fluorescence‐activated cell sorting revealed that the high‐ROS pollen germinated with a frequency that was 35‐fold higher than the low‐ROS pollen, supporting a model in which a significant fraction of a flower's pollen remains in a low metabolic or dormant state even after hydration. The ability to use flow cytometry to quantify ROS dynamics within a large pollen population was shown by dose‐dependent alterations in DCF‐fluorescence in response to oxidative stress or antioxidant treatments. HS treatments (35°C) increased ROS levels, which correlated with a ~60% reduction in pollen germination. These results demonstrate the potential of using flow cytometry‐based approaches to investigate metabolic changes during stress responses in pollen.     

Spatial pattern of invasive and native graminoids in the Brazilian cerrado

Plant Ecology - Invasive grasses are an important threat in tropical savannas and grasslands and may be affected by natural and anthropogenic features of the environment. They may affect native...