γ-Linolenic acid in maternal milk drives cardiac metabolic maturation.

Birth presents a metabolic challenge to cardiomyocytes as they reshape fuel preference from glucose to fatty acids for postnatal energy production1,2. This adaptation is triggered in part by post-partum environmental changes3, but the molecules orchestrating cardiomyocyte maturation remain unknown. Here we show that this transition is coordinated by maternally supplied γ-linolenic acid (GLA), an 18:3 omega-6 fatty acid enriched in the maternal milk. GLA binds and activates retinoid X receptors4 (RXRs), ligand-regulated transcription factors that are expressed in cardiomyocytes from embryonic stages. Multifaceted genome-wide analysis revealed that the lack of RXR in embryonic cardiomyocytes caused an aberrant chromatin landscape that prevented the induction of an RXR-dependent gene expression signature controlling mitochondrial fatty acid homeostasis. The ensuing defective metabolic transition featured blunted mitochondrial lipid-derived energy production and enhanced glucose consumption, leading to perinatal cardiac dysfunction and death. Finally, GLA supplementation induced RXR-dependent expression of the mitochondrial fatty acid homeostasis signature in cardiomyocytes, both in vitro and in vivo. Thus, our study identifies the GLA-RXR axis as a key transcriptional regulatory mechanism underlying the maternal control of perinatal cardiac metabolism.

Proteomic analysis of phytopathogenic fungus Botrytis cinerea as a potential tool for identifying pathogenicity factors, therapeutic targets and for basic research.

Botrytis cinerea is a phytopathogenic fungus causing disease in a substantial number of economically important crops. In an attempt to identify putative fungal virulence factors, the two-dimensional gel electrophoresis (2-DE) protein profile from two B. cinerea strains differing in virulence and toxin production were compared. Protein extracts from fungal mycelium obtained by tissue homogenization were analyzed. The mycelial 2-DE protein profile revealed the existence of qualitative and quantitative differences between the analyzed strains. The lack of genomic data from B. cinerea required the use of peptide fragmentation data from MALDI-TOF/TOF and ESI ion trap for protein identification, resulting in the identification of 27 protein spots. A significant number of spots were identified as malate dehydrogenase (MDH) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). The different expression patterns revealed by some of the identified proteins could be ascribed to differences in virulence between strains. Our results indicate that proteomic analysis are becoming an important tool to be used as a starting point for identifying new pathogenicity factors, therapeutic targets and for basic research on this plant pathogen in the postgenomic era.

The capsid protein of a plant single-stranded RNA virus is modified by O-linked N-acetylglucosamine.

Plum pox virus (PPV) is a member of the Potyvirus genus of plant viruses. Labeling with UDP-[3H]galactose and galactosyltransferase indicated that the capsid protein (CP) of PPV is a glycoprotein with N-acetylglucosamine terminal residues. Mass spectrometry analysis of different PPV isolates and mutants revealed O-linked N-acetylglucosamination, a modification barely studied in plant proteins, of serine and/or threonine residues near the amino end of PPV CP. CP of PPV virions is also modified by serine and threonine phosphorylation, as shown by Western blot analysis with anti-phosphoserine and anti-phosphothreonine antibodies. Thus, "yin-yang" glycosylation and phosphorylation may play an important role in the regulation of the different functions in which the potyviral CP is involved.