Knockdown of the plastid-encoded acetyl-CoA carboxylase gene uncovers functions in metabolism and development

De novo fatty acid biosynthesis in plants relies on a prokaryotic-type acetyl-CoA carboxylase (ACCase) that resides in the plastid compartment. The enzyme is composed of four subunits, one of which is encoded in the plastid genome, whereas the other three subunits are encoded by nuclear genes. The plastid gene (accD) encodes the β-carboxyltransferase subunit of ACCase and is essential for cell viability. To facilitate the functional analysis of accD, we pursued a transplastomic knockdown strategy in tobacco (Nicotiana tabacum). By introducing point mutations into the translational start codon of accD, we obtained stable transplastomic lines with altered ACCase activity. Replacement of the standard initiator codon AUG with UUG strongly reduced AccD expression, whereas replacement with GUG had no detectable effects. AccD knockdown mutants displayed reduced ACCase activity, which resulted in changes in the levels of many but not all species of cellular lipids. Limiting fatty acid availability caused a wide range of macroscopic, microscopic, and biochemical phenotypes, including impaired chloroplast division, reduced seed set, and altered storage metabolism. Finally, while the mutants displayed reduced growth under photoautotrophic conditions, they showed exaggerated growth under heterotrophic conditions, thus uncovering an unexpected antagonistic role of AccD activity in autotrophic and heterotrophic growth.

Analysis of the only plastid genome-encoded fatty acid biosynthesis gene reveals functions in plastid division and seed development, and antagonistic roles in autotrophic and heterotrophic growth.     

Platelet-activating factor in human endometrium

Platelet-activating factor (PAF) is a phospholipid actively produced by human endometrium and deeply involved in the processes of ovoimplantation and labor. We recently found that PAF represents a new autocrine growth factor for a human adenocarcinoma cell line, HEC-1A. Indeed, biologically active PAF is synthesized by HEC-1A cells, under progesterone control. In HEC-1A cells, PAF regulates intracellular calcium concentration ([Ca²⁺]), DNA synthesis and expression of early oncogenes. All these effects are blocked by the receptor antagonist L659,989. However, while nanomolar concentrations of PAF mobilize [Ca²⁺], only micromolar concentrations affect cell growth, suggesting heterogeneity of PAF receptors or signaling. Two distinct populations of PAF receptors are present in HEC-1A cells, which bind PAF in nanomolar and micromolar concentrations, respectively. Since HEC-1A cells are producing elevated concentrations of PAF and micromolar concentrations of the PAF antagonist L659,989 inhibit cell proliferation, an autocrine role for PAF is suggested in HEC-1A cells.     

Thermal behaviour of a heterothermic enzyme: A4 lactate dehydrogenase from Triturus cristatus

The behaviour of T. cristatus A₄ lactate dehydrogenase at different temperatures was studied on the pure isoenzyme. The molecule displays a number of properties which do not conform to any current model of biochemical adaptation to temperature. Our hypothesis is that the structure of newt LDH evolved is such a way to become able to sustain its physiological action over the entire thermal range of the species, and thus no adjustment in kinetic features is needed when temperature varies.     

MiR‐29 coordinates age‐dependent plasticity brakes in the adult visual cortex

The authors regret having omitted grant attributions in the original publication. The funding section is herewith updated to reflect the change. “Funding attributed to Tommaso Pizzorusso was provided by EPIGEN Flagship project and PRIN2017HM8FA, funding attributed to Alessandro Cellerino was provided by Fondazione Pisa ETHERNA project, funding attributed to Pierre Baldi was provided by NIH (grant NIH {"type":"entrez-nucleotide","attrs":{"text":"GM123558","term_id":"221306858","term_text":"GM123558"}}GM123558), funding attributed to Jessica Kwok was provided by the Leverhulme Trust project grant (RPG‐2018‐100).”     

Evidences of olive pollination date variations in relation to spring temperature trends

Airborne pollen concentration patterns reflect flowering phenology of a given species, and it may be a sensitive regional indicator in climate change studies. This paper presents the relationship between a strategic biological event, such as olive flowering, and the air temperature trend, registered over a large scale (1982–2007) in the Umbria region. The aim of the study was to determine relationships between phenological behaviour (flowering) of olive trees and the air temperature trend (1982–2007) in the Umbria region. The phenological data on flowering phase were registered indirectly through an aerobiological monitoring technique. The obtained results showed a strong relationship between phenology and thermal trend. This characteristic was confirmed from results of correlations between temperature (mean temperature from 1st March) and flowering dates, especially that of full flowering (r = −0.9297). Moreover, the results showed an advance trend of 6, 8 and 10 days, respectively of start, full and end of flowering dates. The advance of the recorded flowering time in this period is to ascribe mainly to the increase of mean temperature and above all to that registered in months of May and June.     

Fluorescence-assisted mismatch analysis (FAMA) for exhaustive screening of the α-galactosidase A gene and detection of carriers in Fabry disease

We used the fluorescence-assisted mismatch analysis (FAMA) method to screen rapidly the α-galactosidase A gene in patients with Fabry disease in order to identify unknown mutations and help define genotype-phenotype correlations in this X-linked lysosomal storage disorder. Chemical cleavage at mismatches on heteroduplex DNA end-labeled with strand-specific fluorescent dyes, reliably detects sequence changes in DNA fragments of up to 1.5 kb and locates them precisely. Exhaustive scanning of the α-galactosidase gene was accomplished on four polymerase chain reaction-generated amplicons, covering all seven exons, the exon-intron boundaries, and 700 bp of 5′-flanking sequence. Mutations were identified in each of the 15 patients studied from nine unrelated kindreds. Among the seven previously undescribed sequence changes, three are obviously pathogenic because they lead to premature protein termination. The other four, a splice-site mutation and three missense mutations, were the only changes found upon complete scanning of the gene and its promoter. In addition, FAMA also detects female heterozygous carriers more dependably than direct sequencing, and thus provides a valuable diagnostic test. In Fabry disease, this molecular criterion is especially important for genetic counseling since heterozygotes can be asymptomatic and their enzymatic values within the normal range. Received: 9 April 1996 / Revised: 8 July 1996