Flower development schedule and AGAMOUS‐like gene expression patterns in two morphs of Nigella damascena (Ranunculaceae) differing in floral architecture

Love‐in‐a‐mist (Nigella damascena) is an annual species of Ranunculaceae native to the Mediterranean Basin, characterized by delicate flowers lying on long lacy bracts. Two floral morphs of N. damascena, designated [P] and [T], differ in the identity and number of perianth organs and in the position of the perianth–androecium boundary on the meristem. They both occur in the wild. Here we describe a precise comparative schedule of floral development in the two morphs. We divided the sequence of developmental events affecting the floral meristem into six stages and related them to the height of the elongating stem and to the time elapsed after the beginning of stem elongation. In addition, we characterized the expression pattern of C‐class genes in floral organs of both morphs in an attempt to better characterize the differences between the two floral groundplans. In the [T] morph an expansion of the expression domain of AGAMOUS (AG) paralogues outside the fertile organs was observed, correlating with the change in identity of the inner perianth organs. Expression of AG‐like genes in the sepal‐like organs suggests these are not identical to true sepals at the molecular level. The morpho‐temporal framework we have defined will allow us to compare various gene expression profiles at targeted developmental stages in both morphs, providing further insight into the molecular control of the floral dimorphism in N. damascena and into the processes underlying the transition from a differentiated (bipartite) to an undifferentiated (unipartite) perianth. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 178 , 608–619.     

Protein O-Fucosyltransferase 1 Expression Impacts Myogenic C2C12 Cell Commitment via the Notch Signaling Pathway

The Notch signaling pathway plays a crucial role in skeletal muscle regeneration in mammals by controlling the transition of satellite cells from quiescence to an activated state, their proliferation, and their commitment toward myotubes or self-renewal. O-fucosylation on Notch receptor epidermal growth factor (EGF)-like repeats is catalyzed by the protein O-fucosyltransferase 1 (Pofut1) and primarily controls Notch interaction with its ligands. To approach the role of O-fucosylation in myogenesis, we analyzed a murine myoblastic C2C12 cell line downregulated for Pofut1 expression by short hairpin RNA (shRNA) inhibition during the time course of differentiation. Knockdown of Pofut1 affected the signaling pathway activation by a reduction of the amount of cleaved Notch intracellular domain and a decrease in downstream Notch target gene expression. Depletion in Pax7⁺/MyoD⁻ cells and earlier myogenic program entrance were observed, leading to an increase in myotube quantity with a small number of nuclei, reflecting fusion defects. The rescue of Pofut1 expression in knockdown cells restored Notch signaling activation and a normal course in C2C12 differentiation. Our results establish the critical role of Pofut1 on Notch pathway activation during myogenic differentiation.     

Combining ecophysiological modelling and quantitative trait locus analysis to identify key elementary processes underlying tomato fruit sugar concentration

A mechanistic model predicting the accumulation of tomato fruit sugars was developed in order (i) to dissect the relative influence of three underlying processes: assimilate supply (S), metabolic transformation of sugars into other compounds (M), and dilution by water uptake (D); and (ii) to estimate the genetic variability of S, M, and D. The latter was estimated in a population of 20 introgression lines derived from the introgression of a wild tomato species (Solanum chmielewskii) into S. lycopersicum, grown under two contrasted fruit load conditions. Low load systematically decreased D in the whole population, while S and M were targets of genotype × fruit load interactions. The sugar concentration positively correlated to S and D when the variation was due to genetic introgressions, while it positively correlated to S and M when the variation was due to changes in fruit load. Co-localizations between quantitative trait loci (QTLs) for sugar concentration and QTLs for S, M, and D allowed hypotheses to be proposed on the processes putatively involved at the QTLs. Among the five QTLs for sugar concentration, four co-localized with QTLs for S, M, and D with similar allele effects. Moreover, the processes underlying QTLs for sugar accumulation changed according to the fruit load condition. Finally, for some genotypes, the processes underlying sugar concentration compensated in such a way that they did not modify the sugar concentration. By uncoupling genetic from physiological relationships between processes, these results provide new insights into further understanding of tomato fruit sugar accumulation.     

Distribution of SUN, OVATE, LC, and FAS in the tomato germplasm and the relationship to fruit shape diversity

Phenotypic diversity within cultivated tomato (Solanum lycopersicum) is particularly evident for fruit shape and size. Four genes that control tomato fruit shape have been cloned. SUN and OVATE control elongated shape whereas FASCIATED (FAS) and LOCULE NUMBER (LC) control fruit locule number and flat shape. We investigated the distribution of the fruit shape alleles in the tomato germplasm and evaluated their contribution to morphology in a diverse collection of 368 predominantly tomato and tomato var. cerasiforme accessions. Fruits were visually classified into eight shape categories that were supported by objective measurements obtained from image analysis using the Tomato Analyzer software. The allele distribution of SUN, OVATE, LC, and FAS in all accessions was strongly associated with fruit shape classification. We also genotyped 116 representative accessions with additional 25 markers distributed evenly across the genome. Through a model-based clustering we demonstrated that shape categories, germplasm classes, and the shape genes were nonrandomly distributed among five genetic clusters (P < 0.001), implying that selection for fruit shape genes was critical to subpopulation differentiation within cultivated tomato. Our data suggested that the LC, FAS, and SUN mutations arose in the same ancestral population while the OVATE mutation arose in a separate lineage. Furthermore, LC, OVATE, and FAS mutations may have arisen prior to domestication or early during the selection of cultivated tomato whereas the SUN mutation appeared to be a postdomestication event arising in Europe.     

Increased oxidative stress induces apoptosis in human cystic fibrosis cells

Oxidative stress results in deleterious cell function in pathologies associated with inflammation. Here, we investigated the generation of superoxide anion as well as the anti-oxidant defense systems related to the isoforms of superoxide dismutases (SOD) in cystic fibrosis (CF) cells. Pro-apoptotic agents induced apoptosis in CF but not in control cells that was reduced by treatment with SOD mimetic. These effects were associated with increased superoxide anion production, sensitive to the inhibition of IκB-α phosphorylation, in pancreatic but not tracheal CF cells, and reduced upon inhibition of either mitochondrial complex I or NADPH oxidase. CF cells exhibited reduced expression, but not activity, of both Mn-SOD and Cu/Zn-SOD when compared to control cells. Although, expression of EC-SOD was similar in normal and CF cells, its activity was reduced in CF cells. We provide evidence that high levels of oxidative stress are associated with increased apoptosis in CFTR-mutated cells, the sources being different depending on the cell type. These observations underscore a reduced anti-oxidant defense mechanism, at least in part, via diminished EC-SOD activity and regulation of Cu/Zn-SOD and Mn-SOD expressions. These data point to new therapeutic possibilities in targeting anti-oxidant pathways to reduce oxidative stress and apoptosis in CF cells.     

Selection for Adaptation to Dietary Shifts: Towards Sustainable Breeding of Carnivorous Fish

Genetic adaptation to dietary environments is a key process in the evolution of natural populations and is of great interest in animal breeding. In fish farming, the use of fish meal and fish oil has been widely challenged, leading to the rapidly increasing use of plant-based products in feed. However, high substitution rates impair fish health and growth in carnivorous species. We demonstrated that survival rate, mean body weight and biomass can be improved in rainbow trout (Oncorhynchus mykiss) after a single generation of selection for the ability to adapt to a totally plant-based diet (15.1%, 35.3% and 54.4%, respectively). Individual variability in the ability to adapt to major diet changes can be effectively used to promote fish welfare and a more sustainable aquaculture.