Chloroplast lipid transfer processes in Chlamydomonas reinhardtii involving a TRIGALACTOSYLDIACYLGLYCEROL 2 (TGD2) orthologue

In plants, lipids of the photosynthetic membrane are synthesized by parallel pathways associated with the endoplasmic reticulum (ER) and the chloroplast envelope membranes. Lipids derived from the two pathways are distinguished by their acyl‐constituents. Following this plant paradigm, the prevalent acyl composition of chloroplast lipids suggests that Chlamydomonas reinhardtii (Chlamydomonas) does not use the ER pathway; however, the Chlamydomonas genome encodes presumed plant orthologues of a chloroplast lipid transporter consisting of TGD (TRIGALACTOSYLDIACYLGLYCEROL) proteins that are required for ER‐to‐chloroplast lipid trafficking in plants. To resolve this conundrum, we identified a mutant of Chlamydomonas deleted in the TGD2 gene and characterized the respective protein, CrTGD2. Notably, the viability of the mutant was reduced, showing the importance of CrTGD2. Galactoglycerolipid metabolism was altered in the tgd2 mutant with monogalactosyldiacylglycerol (MGDG) synthase activity being strongly stimulated. We hypothesize this to be a result of phosphatidic acid accumulation in the chloroplast outer envelope membrane, the location of MGDG synthase in Chlamydomonas. Concomitantly, increased conversion of MGDG into triacylglycerol (TAG) was observed. This TAG accumulated in lipid droplets in the tgd2 mutant under normal growth conditions. Labeling kinetics indicate that Chlamydomonas can import lipid precursors from the ER, a process that is impaired in the tgd2 mutant.     

On the serial homology of the pectoral and pelvic girdles of tetrapods

While fore‐ and hindlimbs are commonly assumed to be serially homologous, the serial homology of the pectoral and pelvic girdles is more ambiguous. We investigate the degree to which a common history, developmental program, and gene network are shared between the girdles relative to the rest of the appendicular skeleton. Paleontological data indicate that pectoral appendages arose millions of years before pelvic appendages. Recent embryological and genetic data suggest that the anatomical similarity between the fore‐ and hindlimbs arose through the sequential, derived deployment of similar developmental programs and gene networks, and is therefore not due to ancestral serial homology. Much less developmental work has however been published about the girdles. Here, we provide the first detailed review of the developmental programs and gene networks of the pectoral and pelvic girdles. Our review shows that, with respect to these programs and networks, there are fewer similarities between pelvic and pectoral girdles than there are between the limbs. The available data therefore support recent hypotheses that the anatomical similarities between the fore‐ and hindlimbs arose during the fin‐to‐limb transition through the derived co‐option of similar developmental mechanisms, while the phylogenetically older pectoral and pelvic girdles have remained more distinct since their evolutionary origin.     

Efficacy of a micro‐encapsulated formulation compared with a sticky barrier for excluding ants from citrus canopies

Inesfly IGR FITO^® is an insecticidal paint containing chlorpyrifos and pyriproxyfen incorporated in a micro‐encapsulated formulation that confers the advantage of releasing active ingredients slowly. In this study, a 15‐cm band of Inesfly IGR FITO^® was painted around citrus trunks. The efficacy of this paint and a sticky barrier to exclude ants from foraging in citrus trees was evaluated in two citrus orchards during the season in two different ant communities, one dominated by Lasius grandis and the other by Linepithema humile. Field results demonstrated that a single application of Inesfly IGR FITO^® at the beginning of the season was highly effective in excluding ants from canopies throughout the season. Inesfly IGR FITO^® provides an efficient and more economical alternative than current ant exclusion strategies used in many perennial crops. Further studies should be performed to determine the effects of this strategy on other pests and on beneficial arthropods in citrus.     

Developmental basis of mammalian digit reduction: a case study in pigs

Digit reduction has occurred in parallel in many mammalian lineages. However, despite this pattern's prevalence, the developmental mechanisms underlying mammalian digit reduction remain controversial. We therefore undertook a study of digit development in the pig (Sus scrofa), a mammal with reduced first, second, and fifth digits. Our results indicate that from its earliest formation, the pig limb bud is significantly narrower than that of the model pentadactyl mammal, mouse. Furthermore, the cartilage condensations of the pig's reduced digits are noticeably smaller than those of their nonreduced counterparts from the time of their formation. In addition, growth rates of pig digits are comparable, as are the patterns of cell death in developing pig and mouse limbs. Taken together, results suggest that pig's first, second, and fifth digits are primarily reduced through evolutionary modifications in the early developmental patterning of their limbs. Results of this study, coupled with those from study of limb development in other mammals, suggest that although major developmental reorganizations (e.g., complete digit or limb loss) during early limb development may be selected against, it may be common for more subtle evolutionary modifications in limb development (e.g., changes in relative digit size) to occur at this time.     

The Wolff-Parkinson-White Pattern in Routine Electrocardiography

Fifteen thousand consecutive electrocardiograms on R.C.A.F. aircrew applicants aged 18 to 24 were studied from the standpoint of incidence, clinical findings and follow-up of the WPW pattern discovered because the ECG was taken as part of the selection procedure. Forty-six cases were discovered (0.3%). All were reviewed and passed as clinically fit except for one with asymptomatic rheumatic heart disease. Two others gave a history suggestive of paroxysmal rapid heart action. None of the 43 men on follow-up have developed evidence of arrhythmia. Thirteen of the 46 showed an intermittent pattern initially or on subsequent follow-up. Fifty to 80% of people with the WPW pattern experience tachycardia, according to the literature. The incidence of tachycardia in this study was much lower (2 in 46 or 4.3%). The WPW pattern is not synonymous with the WPW syndrome, and iatrogenic heart disease must be avoided in fit young men in whom the WPW pattern is discovered because of routine electrocardiography.