The short-term responses of glutathione and phytochelation synthetic pathways genes to additional nitrogen under cadmium stress in poplar leaves

Earlier it was noticed that the supplementary nitrogen to nutritive solution of the cadmium stressed (Cd-stressed) plants can alleviate the toxic effects of this metal on the plants and improve plant growth performance. But the underlying mechanisms of such detoxification effect of nitrogen were not studied. In this study, a ten-day responses of related nitrogen-synthesized genes including γ-glutamylcysteine synthetase (γ-GCs), glutathione synthetase (ECGs) and phytochelatin synthase (PCs) involved in glutathione (ECG) and phytochelation (PC) synthetic pathways were examined. The plant growth performance and leaf chlorophyll content were examined at the final harvest. It was shown that the supplement of additional nitrogen to poplar plants under cadmium stress could significantly up-regulate the expression levels of γ-GCs, ECGs and PCs genes in plant leaves during the first 12 hours. Furthermore, cadmium stressed plants with additional nitrogen supplement showed significant enhancement in growth performance and increase in leaf chlorophyll content compared to sole cadmium stressed plants. Our results suggest that additional nitrogen could stimulate a short-term defense system in poplar plants through ECG and PC synthetic pathways. It is contribute to the alleviation of the toxic symptoms in polar plants caused by cadmium stress. This study provides a potential method to render harmless cadmium toxicity in stressed plants with nitrogen fertilization.     

Physiological and proteomic analysis of mycorrhizal <Emphasis Type="Italic">Pinus massoniana</Emphasis> inoculated with <Emphasis Type="Italic">Lactarius insulsus</Emphasis> under drought stress

This study aimed to investigate physiological and protein expression alterations of mycorrhizal Pinus massoniana Lamb. inoculated with Lactarius insulsus in response to drought stress. The P. massoniana seedlings were inoculated with L. insulsus (Li group) and ectomycorrhized fungal-free filtrate (control, CK group), respectively. After two and a half years, all the plants were exposed to a simulate drought condition without water for 21 days. The soil relative water content (SRWC), wilting degree (WD) and wilting rate (WR) of the plants were measured and root proteome was analyzed based on two-dimensional gel electrophoresis (2-DE), respectively at four time points as 0, 7, 14 and 21 days during the whole drought period. Finally, the electrospray ionization mass spectrometry (ESI-MS) was used to identify the differentially expressed proteins (DEPs) between Li and CK groups. The SRWC was higher, while WR and WD were lower in Li group, compared with that in CK group. Based on 2-DE and ESI-MS, 22 DEPs were identified between Li and CK groups during drought stress. Among them, four proteins had the annotated information in relevant databases, including 1,4-benzoquinone reductase, PSCHI4, ribosomal protein L16 (RPL16) and AINTEGUMENTA-like (AIL) protein. Mycorrhizal P. massoniana inoculated with L. insulsus achieved an enhanced drought resistance as compared to the non-mycorrhizal, and the altered protein expressions such as 1,4-benzoquinone reductase, PSCHI4, RPL16, and AIL might contribute to the improved resistance under drought stress.     

Effects of exogenous spermidine on antioxidant system of tomato seedlings exposed to high temperature stress

The effects of foliar spraying with spermidine (Spd) on antioxidant system in tomato (Lycopersicon esculentum Mill.) seedlings were investigated under high temperature stress. The high temperature stress significantly inhibited plant growth and reduced chlorophyll (Chl) content. Application of exogenous 1 mM Spd alleviated the inhibition of growth induced by the high temperature stress. Malondialdehyde (MDA), hydrogen peroxide (H₂O₂) content and superoxide anion (O₂) generation rate were significantly increased by the high temperature stress, but Spd significantly reduced the accumulation of reactive oxygen species (ROS) and MDA content under the stress. The high temperature stress significantly decreased glutathione (GSH) content and activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR), but increased contents of dehydroascorbic acid (DHA), ascorbic acid (AsA), and oxidized glutathione (GSSG) in tomato leaves. However, Spd significantly increased the activities of antioxidant enzymes, levels of antioxidants and endogenous polyamines in tomato leaves under the high temperature stress. In addition, to varying degrees, Spd regulated expression of MnSOD, POD, APX2, APX6, GR, MDHAR, DHAR1, and DHAR2 genes in tomato leaves exposed to the high temperature stress. These results suggest that Spd could change endogenous polyamine levels and alleviate the damage by oxidative stress enhancing the non-enzymatic and enzymatic antioxidant system and the related gene expression.     

Ecological speciation in sympatric palms: 1. Gene expression,selection and pleiotropy

Ecological speciation requires divergent selection, reproductive isolation and a genetic mechanism to link the two. We examined the role of gene expression and coding sequence evolution in this process using two species of Howea palms that have diverged sympatrically on Lord Howe Island, Australia. These palms are associated with distinct soil types and have displaced flowering times, representing an ideal candidate for ecological speciation. We generated large amounts of RNA‐Seq data from multiple individuals and tissue types collected on the island from each of the two species. We found that differentially expressed loci as well as those with divergent coding sequences between Howea species were associated with known ecological and phenotypic differences, including response to salinity, drought, pH and flowering time. From these loci, we identified potential ‘ecological speciation genes’ and further validate their effect on flowering time by knocking out orthologous loci in a model plant species. Finally, we put forward six plausible ecological speciation loci, providing support for the hypothesis that pleiotropy could help to overcome the antagonism between selection and recombination during speciation with gene flow.     

Genome-wide mapping of copy number variations in commercial hybrid pigs using a high-density SNP genotyping array

Copy number variations (CNVs) are important forms of structural variation in human and animals and can be considered as a major genetic component of phenotypic diversity. Here we used the Illumina PorcineSNP60 BeadChip V2 and a DLY [Duroc × (Large White × Landrace)] commercial hybrid population to identify 272 CNVs belonging to 165 CNV regions (CNVRs), of which 66 are new. As CNVRs are specific to origin of population, our DLY-specific data is an important complementary to the existing CNV map in the pig genome. Eight CNVRs were selected for validation by quantitative real-time PCR (qRT-PCR) and the accurate rate was high (87.25%). Gene function analysis suggested that a common CNVR may play an important role in multiple traits, including growth rate and carcass quality.     

Oscillatory growth behavior of multistream instabilities

Multistream instabilities in the one-dimensional Vlasov?Poisson system are studied numerically by using plasmas with multi-humped electron distributions. The evolution of the total wave energy of the plasma oscillations excited by (numerical) noise consists of transient, growth, and nonlinear saturation stages. It is found that, in the growth stage, the total wave energy oscillates for odd number of streams, but it does not oscillate for even number of streams. It is also found that different spectral (Fourier) modes can dominate different stages of the “linear” growth and nonlinear saturation stages.