No abstract

Leaf color is one of the well-sought traits in breeding program for Anthurium andraeanum Lind. Knowledge of mechanisms in anthuriums to produce leaves with different shades of green would help to effectively select desirable traits. In this study, the micro- and ultra-structural and physiological features of leaves on wild type and leaf color mutants (dark green, rubescent, etiolated, albino) in A. andraeanum ‘Sonate’ were analyzed. Results show that chloroplasts of leaf color mutants exhibited abnormal morphology and distribution. Using next generation sequencing technology followed by de novo assembly, leaf transcriptomes comprising of 41,017 unigenes with an average sequence length of 768 bp were produced from wild type and rubescent mutant. From the 27,539 (67.1%) unigenes with annotated functions, 858 significantly differently expressed genes (DEGs) were identified, consisting of 446 up-regulated genes and 412 down-regulated genes. Genes that affect chloroplasts development and division, and chlorophyll biosynthesis were included in the down-regulated DEGs. Quantitative real-time PCR (qRT-PCR) analysis validated that the expression level of those genes was significantly lower in the rubescent, etiolated, and albino mutant compared to wild type plants, which concurs with the differences in micro- and ultra-structures and physiological features between these two types of plants. Conclusively, the leaf color formation is greatly affected by the activity of chloroplast development and pigment biosynthesis. And the possible formation pathway of leaf color mutant of A. andraeanum ‘Sonate’ is deduced based on our results.

We have cloned and characterized cDNAs encoding the zebrafish IGF ligands and receptors. Sequence comparison showed that the primary structures of zebrafish IGF-I, IGF-II, and IGF-I receptors (IGF-IRs) have been highly conserved in vertebrates. In contrast to the presence of a single IGF-IR gene in mammals, two distinct IGF-IR genes, termed igf-1ra and igf-1rb, were found in zebrafish. Structural and phylogenetic analyses indicated that both genes are orthologous to the human igf-1r gene. Immunoprecipitation studies with specific antibodies showed that both IGF-IR genes are expressed and both receptors bind to IGFs and des(1-3)IGF-I, but not to insulin. The spatio-temporal expression patterns of the two IGF-IRs and their ligands were determined using a combination of RT-PCR, whole mount in situ hybridization, and immunocytochemistry. Transcripts for both IGF-I and -II mRNAs were found throughout embryogenesis in a ubiquitous manner. In adult tissues, IGF-I mRNA was more abundant in liver and testis, and its level was increased after GH treatment, whereas IGF-II mRNA was not regulated by GH. IGF-IRa and IGF-IRb mRNAs and proteins were expressed in overlapping spatial domains, but exhibited distinct temporal expression patterns. In particular, the relative level of IGF-IRa mRNA was low during early embryogenesis and increased in the hatched larva, whereas the situation was reversed for IGF-IRb mRNA. In adult zebrafish, the overall tissue distribution patterns of the two IGF-IRs were similar, but there were differences in their cellular localization and relative abundance in defined cells/regions. The differential expression pattern of IGF-IRa and IGF-IRb suggest that they may play distinct roles in regulating the growth and development of zebrafish.

CRISPR-Cas9 components delivered by engineered exosomes achieve genome editing in recipient cells.

Leaf senescence is a typical symptom in plants exposed to dark and may be regulated by plant growth regulators. The objective of this study was to determine whether exogenous application of melatonin (N-acetyl-5-methoxytryptamine) suppresses dark-induced leaf senescence and the effects of melatonin on reactive oxygen species (ROS) scavenging system and chlorophyll degradation pathway in perennial grass species. Mature perennial ryegrass (Lolium perenne L. cv. ‘Pinnacle’) leaves were excised and incubated in 3 mM 2-(N-morpholino) ethanesulfonic buffer (pH 5.8) supplemented with melatonin or water (control) and exposed to dark treatment for 8 days. Leaves treated with melatonin maintained significantly higher endogenous melatonin level, chlorophyll content, photochemical efficiency, and cell membrane stability expressed by lower electrolyte leakage and malondialdehyde (MDA) content compared to the control. Exogenous melatonin treatment also reduced the transcript level of chlorophyll degradation-associated genes and senescence marker genes (LpSAG12.1, Lph36, and Lpl69) during the dark treatment. The endogenous O2- production rate and H2O2 content were significantly lower in these excised leaves treated with melatonin compared to the water control. Exogenous melatonin treatment caused increases in enzymatic activity and transcript levels of superoxide dismutase and catalase but had no significant effects on ascorbate peroxidase, glutathione reductase, dehydroascorbate reductase, and monohydroascorbate reductase. The content of non-enzymatic antioxidants, such as ascorbate and dehydroascorbate, were decreased by melatonin treatment, while the content of glutathione and oxidized glutathione was not affected by melatonin. These results suggest that the suppression of dark-induced leaf senescence by exogenous melatonin may be associated with its roles in regulating ROS scavenging through activating the superoxide dismutase-catalase enzymatic antioxidant pathway and down-regulating chlorophyll degradation in perennial ryegrass.

Quantitative real-time reverse transcriptase polymerase chain reaction (qRT-PCR) is an effective method for quantifying expression levels of target genes. The accuracy of qRT-PCR results is largely dependent on the selection of stable reference genes. The stability of reference gene expression may vary with plant species and environmental conditions. The objective of this study was to select stable reference genes for qRT-PCR analysis of target genes in different organs under different abiotic stresses for a perennial grass species, bermudagrass (Cynodon dactylon). The stability of eight potential reference genes (TUB, ACT, GAPDH, EF1α, TIP41, PP2A, CACS and UPL7) was evaluated under four different abiotic stresses (salt, drought, cold and heat) and in leaves and roots of bermudagrass. Four programs (geNorm, NormFinder, BestKeeper and RefFinder) were employed to evaluate the stability of reference gene expression and to identify the most stable reference genes for bermudagrass. Eight potential reference genes exhibited differential expression stability in leaves and roots under salt, drought, cold and heat stress. The expression levels of PP2A and CACS were stable in roots and leaves under salt stress, in leaves under drought stress and in roots exposed to cold and heat stress. EF1α and TIP41 expression was stable in roots of drought-stressed plants. UPL7, TUB and GAPDH were stably expressed in leaves under cold stress. Expression levels of PP2A and TIP41 were stable in leaves under heat stress. The use of the reference genes identified as internal controls for examination of gene expression patterns and quantification of expression levels of target genes will enable accurate qRT-PCR analysis in bermudagrass.

Streptococcus suis serotype 2 (SS2) induced sepsis and meningitis are often accompanied by bacteremia. However, the mechanism whereby it helps S. suis to evade PMN-mediated phagocytosis remain unclear. Because of the central roles of bacteria-human fibrinogen (hFg) interaction in innate immunity, here, a proteomics based Far-western blotting (PBFWB) was developed to identify the fibrinogen-binding surface proteins of S. suis (SsFBPs) on a large-scale. And then thirteen potential SsFBPs were identified by PBFWB and we selected seven potential surface proteins to further confirm their binding ability to hFg, of which the gene mutant strains of MRP displayed significantly decrease in binding to immobilized hFg. Additionally, the polyclonal antibodies against Enolase were found to significantly inhibit the binding of SS2 to hFg. Strikingly, MRP and Enolase were found to improve the antiphagocytic ability of SS2 to PMNs by interacting with hFg and enhance the survival of SS2 in human blood. Taken together, the PBFWB method provides useful clues to the bacteria-host interactions. These studies firstly disclose MRP and Enolase were involved in immune evasion of SS2 at least in part by binding to Fg, which make them potential targets for therapies for SS2 infection.

HighlightLeaf senescence regulated by abscisic acid, cytokinins, and ethyelene was associated with transcriptional regulation of LpPPH. Orthologous PPH genes share conserved cis-elements potentially targeted by hormonal signaling pathways.