Coupling of different antioxidative systems in rice under the simultaneous influence of selenium and cadmium.

Selenium (Se) elevates the antioxidant ability of rice against cadmium (Cd) stress, but previous studies only focused on the variation in antioxidant enzymes or nonenzymatic substances induced by Se under Cd stress and ignored the relationships between different antioxidant parameters during the interaction. Here, hydroponic experiments with rice were performed by adding both Cd and Se at doses in the range of 0-50 µM to explore the physiological responses of rice and their relationships in the presence of different levels of Se and Cd. Exogenous Cd markedly promoted the activity of antioxidant enzymes with the exception of catalase (CAT) and the concentration of nonenzymatic substances in aerial parts. Se enhanced the antioxidant capacity by improving the activities of all the enzymes tested in this study and increasing the concentrations of nonenzymatic compounds. The couplings among different antioxidant substances within paddy rice were then determined based on cluster and linear fitting results and their metabolic process and physiological functions. The findings specifically highlight that couplings among the ascorbic acid (AsA)-glutathione (GSH) cycle, glutathione synthase (GS)-phytochelatin synthetase (PCS) coupling system and glutathione peroxidase (GPX)-superoxide dismutase (SOD) coupling system in aerial parts helps protect plants from Cd stress. These coupling systems form likely due to the fact that one enzyme generated a product that could be the substrate for another enzyme. Noticeably, such coupling systems do not emerge in roots because the stronger damage to roots than other organs activates the ascorbate peroxidase (APX)-GPX-CAT and PCS-GS-SOD systems with distinct functions and structures. This study provides new insights into the detoxification mechanisms of rice caused by the combined effect of Se and Cd.

Identification and candidate gene screening of qCIR9.1, a novel QTL associated with anther culturability in rice (Oryza sativa L.).

KEY MESSAGE: A novel QTL, qCIR9.1, that controls callus induction rate in anther culture was identified on chromosome 9 in rice, and based on RNA-seq data, Os09g0551600 was the most promising candidate gene. Anther culture, a doubled haploid (DH) technique, has become an important technology in many plant-breeding programmes. Although anther culturability is the key factor in this technique, its genetic mechanisms in rice remain poorly understood. In this study, we mapped quantitative trait loci (QTLs) responsible for anther culturability by using 192 recombinant inbred lines (RILs) derived from YZX (Oryza sativa ssp. indica) × 02428 (Oryza sativa ssp. japonica) and a high-density bin map. A total of eight QTLs for anther culturability were detected in three environments. Among these QTLs, a novel major QTL for callus induction rate (CIR) named qCIR9.1 was repeatedly mapped to a ~ 100 kb genomic interval on chromosome 9 and explained 8.39-14.14% of the phenotypic variation. Additionally, RNA sequencing (RNA-seq) was performed for the parents (YZX and 02428), low- (L-Pool) and high-CIR RILs (H-Pool) after 16 and 26 days of culture. By using the RNA of the bulked RILs for background normalization, the number of differentially expressed genes (DEGs) both between the parents and between the bulked RILs after 26 days of culture was drastically reduced to only 78. Among these DEGs, only one gene, Os09g0551600, encoding a high-mobility group (HMG) protein, was located in the candidate region of qCIR9.1. qRT-PCR analysis of Os09g0551600 showed the same results as RNA-seq, and the expression of this gene was decreased in the low-callus-induction parent (YZX) and L-Pool. Our results provide a foundational step for further cloning of qCIR9.1 and will be very useful for improving anther culturability in rice.

Atorvastatin enhances angiogenesis to reduce subdural hematoma in a rat model.

BACKGROUND AND PURPOSE: Statins are active in reducing plasma lipids, suppressing inflammation and promoting angiogenesis. Because angiogenesis is critical for the absorbance of subdural hematoma (SDH), we hypothesize that atorvastatin promotes angiogenesis to enhance hematoma absorption. METHODS: SDH was induced in adult Wistar rats and treated with 3mg/kg, 8mg/kg of atorvastatin, or vehicle saline daily for 7days. The treated rats were examined for the level of CD34+/CD133+ endothelial progenitor cells (EPCs) in the circulation by flow cytometry, hematoma volumes by magnetic resonance imaging (MRI), and changes in cognitive functions. We also examined angiogenesis in the hematoma wall by transmission electronic microscopy and immunohistochemistry for the expression of vascular endothelial growth factor (VEGF), matrix metalloprotease 9 (MMP 9) and angiopoietin. RESULTS: SDH volume was significantly reduced and neurological deficits improved in rats receiving the low dose atorvastatin compared to those receiving either the high dose of atorvastatin or saline. Consistent with these outcome measures, the low dose atorvastatin increased the expression of angiopoient-1 and VEGF and reduced MMP9 expression in the connective tissue of the SDH wall, resulting in an increased vascular density and enhanced vascular maturation. CONCLUSIONS: The low-dose atorvastatin is effective in reducing SDH and improving neurological deficits in a rat model, primarily by promoting angiogenesis and vascular maturation.