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.

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

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.

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.