Connexin Expression Is Altered in Liver Development of Yotari (dab1 -/-) Mice

Disabled-1 (Dab1) protein is an intracellular adaptor of reelin signaling required for prenatal neuronal migration, as well as postnatal neurotransmission, memory formation and synaptic plasticity. Yotari, an autosomal recessive mutant of the mouse Dab1 gene is recognizable by its premature death, unstable gait and tremor. Previous findings are mostly based on neuronal abnormalities caused by Dab1 deficiency, but the role of the reelin signaling pathway in nonneuronal tissues and organs has not been studied until recently. Hepatocytes, the most abundant cells in the liver, communicate via gap junctions (GJ) are composed of connexins. Cell communication disruption in yotari mice was examined by analyzing the expression of connexins (Cxs): Cx26, Cx32, Cx37, Cx40, Cx43 and Cx45 during liver development at 13.5 and 15.5 gestation days (E13.5 and E15.5). Analyses were performed using immunohistochemistry and fluorescent microscopy, followed by quantification of area percentage covered by positive signal. Data are expressed as a mean±SD and analyzed by one-way ANOVA. All Cxs examined displayed a significant decrease in yotari compared to wild type (wt) individuals at E13.5. Looking at E15.5 we have similar results with exception of Cx37 showing negligible expression in wt. Channels formation triggered by pathological stimuli, as well as propensity to apoptosis, was studied by measuring the expression of Pannexin1 (Panx1) and Apoptosis-inducing factor (AIF) through developmental stages mentioned above. An increase in Panx1 expression of E15.5 yotari mice, as well as a strong jump of AIF in both phases suggesting that yotari mice are more prone to apoptosis. Our results emphasize the importance of gap junction intercellular communication (GJIC) during liver development and their possible involvement in liver pathology and diagnostics where they can serve as potential biomarkers and drug targets.

Breeding Potential of Maize Germplasm Line GEMS-0067 for High Amylose Proportion

Maize varieties with high amylose proportion are more valuable for starch industry. The SBEⅡb gene encodes one of the starch branching isozymes (SBEⅠ, SBEⅡa, and SBEⅡb). Its recessive mutant amylose-extender (ae/sbe2b) decreases the total activities of SBEs and increases amylose proportion up to 60%. Here, the breeding potential of introduced germplasm line GEMS-0067 was evaluated by genotyping and phenotyping. The deletion of the ninth exon of the SBEⅡb gene, high amylose proportion, and the typical irregular granules suggested that this germplasm line was derived from the same resource of high amylose line AE11. The gelatinization and thermal properties, and degree of polymerization of starch chain showed its advantages used for high amylose breeding. However, the negative correlation between amylose proportion and starch content, as well as ker-nel filling characteristics should be overcome during breeding process.

AUREA maintains the balance between chlorophyll synthesis and adventitious root formation in tomato

Flooding tolerance is an important trait for tomato breeding. In this study, we obtained a recessive mutant exhibiting highly enhanced submergence resistance. Phenotypical analyses showed that this resistant to flooding (rf) mutant displays slightly chlorotic leaves and spontaneous initiation of adventitious roots (ARs) on stems. The mutation was mapped to the phytochromobilin synthase gene AUREA (AU), in which a single amino acid substitution from asparagine to tyrosine occurred. In addition to the classic function of AU in phytochrome and chlorophyll biogenesis in leaves, we uncovered its novel role in mediating AR formation on stems. We further observed temporal coincidence of the two phenotypes in the rf mutant: chlorosis and spontaneous AR formation and revealed that AU functions by maintaining heme homeostasis. Interestingly, our grafting results suggest that heme might play roles in AR initiation via long-distance transport from leaves to stems. Our results present genetic evidence for the involvement of the AU–heme oxygenase-1–heme pathway in AR initiation in tomato. As fruit production and yield in the rf mutant are minimally impacted, the mutation identified in this study may provide a target for biotechnological renovation of tomato germplasm in future breeding.

The Impact of Dominance on Adaptation in Changing Environments

Natural environments are seldom static and therefore it is important to ask how a population adapts in a changing environment. We consider a finite, diploid population evolving in a periodically changing environment and study how the fixation probability of a rare mutant depends on its dominance coefficient and the rate of environmental change. We find that, in slowly changing environments, the effect of dominance is the same as in the static environment, that is, if a mutant is beneficial (deleterious) when it appears, it is more (less) likely to fix if it is dominant. But, in fast changing environments, the effect of dominance can be different from that in the static environment and is determined by the mutant’s fitness at the time of appearance as well as that in the time-averaged environment. We find that, in a rapidly varying environment that is neutral on average, an initially beneficial (deleterious) mutant that arises while selection is decreasing (increasing) has a fixation probability lower (higher) than that for a neutral mutant as a result of which the recessive (dominant) mutant is favored. If the environment is beneficial (deleterious) on average but the mutant is deleterious (beneficial) when it appears in the population, the dominant (recessive) mutant is favored in a fast changing environment. We also find that, when recurrent mutations occur, dominance does not have a strong influence on evolutionary dynamics.

The impact of dominance on adaptation in changing environments

Natural environments are seldom static and therefore it is important to ask how a population adapts in a changing environment. We consider a finite, diploid population evolving in a periodically changing environment and study how the fixation probability of a rare mutant depends on its dominance coefficient and the rate of environmental change. We find that in slowly changing environments, the effect of dominance is the same as in the static environment, that is, if a mutant is beneficial (deleterious) when it appears, it is more (less) likely to fix if it is dominant. But in fast changing environments, the effect of dominance can be different from that in the static environment and is determined by the mutant’s fitness at the time of appearance as well as that in the time-averaged environment. We find that in a rapidly varying environment which is neutral on average, an initially beneficial (deleterious) mutant that arises while selection is decreasing (increasing) has a fixation probability lower (higher) than that for a neutral mutant as a result of which the recessive (dominant) mutant is favored. If the environment is beneficial (deleterious) on average but the mutant is deleterious (beneficial) when it appears in the population, the dominant (recessive) mutant is favored in a fast changing environment. We also find that when recurrent mutations occur, dominance does not have a strong influence on evolutionary dynamics.

A novel cucumber albino mutant caused by chloroplast development deficiency

Background Photosynthesis is a fundamental process for plant growth and development dependent on a precise network, including formation of chloroplast and chlorophyll synthesis. Chloroplast development deficiency could lead to albinism in higher plant. Results Here, we report a cucumber albino recessive mutant that processed white cotyledons under light condition and is unable to produce first true leaf. Meanwhile, albino mutant could grow out creamy green cotyledons under dark condition but died after exposing to light. Using fluorescence microscopy and transmission electron microscope (TEM), impaired chloroplasts were observed. We identified 7 and 3 differentially expressed genes (DEG) involved in Chlorophyll metabolism and Methylerythritol 4-phosphate (MEP) pathway through transcriptome analysis, respectively. We also examined the reported homologous genes for albino mutants from other plants. Two of 12 genes, TOC159 and DXS1, were up-regulated in cucumber albino mutants as well. The reliability of RNA sequencing results were further confirmed by real-time quantitative PCR (qPCR). Conclusions Taken together, we elaborate the differences between albino mutant and normal seedlings from a single cucumber progeny. This mutant is a new material to study protoplast development.

Clinical Probe of Cyp2C8*2 Mutants in a Malaria Hyperendemic Zone: Evidence from North-Central, Nigeria

Background: A tremendous level of success has been achieved since the introduction of chloroquine and the combination of amodiaquine and artemisinin for the treatment of both complicated and uncomplicated malaria infections in sub-Saharan Africa. However, the recent discovery of drug resistant strains of Plasmodium falciparum (P.f.) and the ability of the parasite to ingest CYP2C8 into its digestive vacuole is of great public health concern. This study probes the occurrence of CYP2C8*2 allelic mutant amongst malaria patients in North-Central Nigeria. Methods: Three hundred and eighty five (385) unrelated study participants were screened for current malaria episodes using routine microscopy and/or rapid diagnostic test strips (RDTs). Chelex extraction method was used for single nucleotide polymorphisms (SNPs) and identification of CYP2C8*2 (805A > T) variant respectively. Wild-type (A) and the defective allele (T) were differentiated with the use of Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP). The results obtained were further validated with Sanger sequencing of a few samples and thereafter, the genotype data were statistically processed. All alleles obtained were in Hardy Weinberg equilibrium. Results: Out of the 385 participants (45.5% Male and 54.5% Female) genotyped for SNPs, 75 (19.5%) had the autosomal recessive mutant trait. Occurrence of mutant traits was gender and ethnic independent (p > 0.05). Yoruba ethnic group recorded a reduction in proportion of genotypic defective CYP2C8*2 allele (T) (1 in every 8 persons) with a carrier percentage of 13.3% compared with Hausa (26.62%); Igbo (25.37%) and other minority ethnic groups (17.6%). Conclusions: A remarkable inter-ethnic differences in autosomal recessive CYP2C8*2 allele was observed. By implication, there is a gradual incursion of genetic drift for poor CQ and AQ-Artemisinin metabolizers among the inhabitants.

Identification and Characterization of Aspergillus nidulans Mutants Impaired in Asexual Development under Phosphate Stress

The transcription factor BrlA plays a central role in the production of asexual spores (conidia) in the fungus Aspergillus nidulans. BrlA levels are controlled by signal transducers known collectively as UDAs. Furthermore, it governs the expression of CDP regulators, which control most of the morphological transitions leading to the production of conidia. In response to the emergence of fungal cells in the air, the main stimulus triggering conidiation, UDA mutants such as the flbB deletant fail to induce brlA expression. Nevertheless, ΔflbB colonies conidiate profusely when they are cultured on a medium containing high H2PO4− concentrations, suggesting that the need for FlbB activity is bypassed. We used this phenotypic trait and an UV-mutagenesis procedure to isolate ΔflbB mutants unable to conidiate under these stress conditions. Transformation of mutant FLIP166 with a wild-type genomic library led to the identification of the putative transcription factor SocA as a multicopy suppressor of the FLIP (Fluffy, aconidial, In Phosphate) phenotype. Deregulation of socA altered both growth and developmental patterns. Sequencing of the FLIP166 genome enabled the identification and characterization of PmtCP282L as the recessive mutant form responsible for the FLIP phenotype. Overall, results validate this strategy for identifying genes/mutations related to the control of conidiation.

Transcriptome Dynamics of Double Recessive Mutant, o2o2o16o16, Reveals the Transcriptional Mechanisms in the Increase of Its Lysine and Tryptophan Content in Maize

In maize, pyramiding of o2 and o16 alleles can greatly improve the nutritional quality of grains. To dissect its molecular mechanism, we created a double recessive mutant line, o2o2o16o16, by introgression of the o2 and o16 alleles into the wild-type maize inbred line, by molecular marker-assisted backcross selection. The kernels (18 day after pollination (DAP), 28 DAP, and 38 DAP) of the o2o2o16o16 mutant and its parent lines were subject to RNA sequencing (RNA-Seq). The RNA-Seq analysis revealed that 59 differentially expressed genes (DEGs) were involved in lysine metabolism and 43 DEGs were involved in tryptophan metabolism. Among them, the genes encoding AK, ASADH, and Dap-F in the lysine synthesis pathway were upregulated at different stages of endosperm development, promoting the synthesis of lysine. Meanwhile, the genes encoding LKR/SDH and L-PO in the lysine degradation pathway were downregulated, inhibiting the degradation of lysine. Moreover, the genes encoding TAA and YUC in the tryptophan metabolic pathway were downregulated, restraining the degradation of tryptophan. Thus, pyramiding o2 and o16 alleles could increase the lysine and tryptophan content in maize. These above results would help to uncover the molecular mechanisms involved in the increase in lysine and the tryptophan content, through the introgression of o2 and o16 alleles into the wild-type maize.