Mutation of Protoporphyrinogen IX Oxidase Gene Causes Spotted and Rolled Leaf and Its Overexpression Generates Herbicide Resistance in Rice.

Protoporphyrinogen IX (Protogen IX) oxidase (PPO) catalyzes the oxidation of Protogen IX to Proto IX. PPO is also the target site for diphenyl ether-type herbicides. In plants, there are two PPO encoding genes, PPO1 and PPO2. To date, no PPO gene or mutant has been characterized in monocotyledonous plants. In this study, we isolated a spotted and rolled leaf (sprl1) mutant in rice (Oryza sativa). The spotted leaf phenotype was sensitive to high light intensity and low temperature, but the rolled leaf phenotype was insensitive. We confirmed that the sprl1 phenotypes were caused by a single nucleotide substitution in the OsPPO1 (LOC_Os01g18320) gene. This gene is constitutively expressed, and its encoded product is localized to the chloroplast. The sprl1 mutant accumulated excess Proto(gen) IX and reactive oxygen species (ROS), resulting in necrotic lesions. The expressions of 26 genes associated with tetrapyrrole biosynthesis, photosynthesis, ROS accumulation, and rolled leaf were significantly altered in sprl1, demonstrating that these expression changes were coincident with the mutant phenotypes. Importantly, OsPPO1-overexpression transgenic plants were resistant to the herbicides oxyfluorfen and acifluorfen under field conditions, while having no distinct influence on plant growth and grain yield. These finding indicate that the OsPPO1 gene has the potential to engineer herbicide resistance in rice.

Changes in ischemic heart disease mortality at the global level and their associations with natural disasters: A 28-year ecological trend study in 193 countries.

BACKGROUND: Natural disasters are believed to be associated with cardiovascular disease. This study aimed to explore the changes in mortality due to ischemic heart disease (IHD) and their associations with natural disasters at the global level. METHODS: Country-specific data on the impact of natural disasters, rates of mortality due to IHD and years of life lost (YLL) and socioeconomic variables were obtained for 193 countries for the period from 1990 to 2017. An ecological trend study was conducted to estimate the changes in the IHD mortality and YLL rates and their associations with natural disasters (occurrence, casualties and total damage). Correlation analyses and multivariate linear regression were used. RESULTS: Significant changes were found in the IHD mortality and YLL rates and the occurrence of disasters between the two equal periods (1990 to 2003 and 2004 to 2017) (p<0.001). The bivariate Pearson correlation test revealed that the trend in the occurrence of natural disasters was positively correlated with trends in the IHD mortality and YLL rates among females and all individuals (p<0.05) and was marginally correlated among males. Multiple linear regression revealed an independent association between the occurrence of natural disasters and the IHD mortality rate among males, females and all individuals (standardized coefficients = 0.163, 0.357 and 0.241, p<0.05), and similar associations were found for the YLL rate (standardized coefficients = 0.194, 0.233 and 0.189, p<0.05). CONCLUSIONS: Our study demonstrated significant changes in the IHD mortality and YLL rates at the global level and their independent associations with natural disasters. Both males and females were vulnerable to natural disasters. These results provide evidence that can be used to support policy making and resource allocation when responding to disasters and developing strategies to reduce the burden of IHD.

Disability-Adjusted Life Years (DALYs) Due to Ischemic Heart Disease (IHD) Associated with Natural Disasters: A Worldwide Population-Based Ecological Study.

Background: Recent studies have reported an association between natural disasters of various kinds and ischemic heart disease (IHD). We investigated the association between Disability-adjusted life years (DALYs) due to IHD and natural disasters and aimed to assess DALYs as a quantification of the burden of IHD related to natural disasters at the global level. Methods: Country-specific data of natural disaster impacts DALYs due to IHD and socioeconomic variables were obtained from open sources over the period of 1990-2013 and 2014-2017. A population-based trend ecological design was conducted to estimate the association between trends in DALYs and natural disasters (occurrence, casualties and total damage), adjusting for socioeconomic variables. Results: Most countries have experienced increases in natural disaster occurrences and decreases in DALYs during this study period. The unadjusted correlation analysis demonstrated a positive and significant correlation between DALYs and natural disasters for females and for both sexes (R = 0.163 and 0.146, p = 0.024 and 0.043), and a marginally significant correlation for males (R = 0.128, p = 0.076). After adjusting for socioeconomic variables, multiple linear regression demonstrated independent associations between the occurrence and DALYs due to IHD for males, females and both sexes (standardized coefficients = 0.192, 0.23 and 0.187, p = 0.016, 0.004 and 0.022). Conclusions: A weak but significantly positive association between natural disaster and IHD was confirmed and quantified at the global level by this DALY metric analysis. Adaptation strategies for natural disaster responses and IHD disease burden reduction need to be developed.

LPS1, Encoding Iron-Sulfur Subunit SDH2-1 of Succinate Dehydrogenase, Affects Leaf Senescence and Grain Yield in Rice.

The iron-sulfur subunit (SDH2) of succinate dehydrogenase plays a key role in electron transport in plant mitochondria. However, it is yet unknown whether SDH2 genes are involved in leaf senescence and yield formation. In this study, we isolated a late premature senescence mutant, lps1, in rice (Oryza sativa). The mutant leaves exhibited brown spots at late tillering stage and wilted at the late grain-filling stage and mature stage. In its premature senescence leaves, photosynthetic pigment contents and net photosynthetic rate were reduced; chloroplasts and mitochondria were degraded. Meanwhile, lps1 displayed small panicles, low seed-setting rate and dramatically reduced grain yield. Gene cloning and complementation analysis suggested that the causal gene for the mutant phenotype was OsSDH2-1 (LOC_Os08g02640), in which single nucleotide mutation resulted in an amino acid substitution in the encoded protein. OsSDH2-1 gene was expressed in all organs tested, with higher expression in leaves, root tips, ovary and anthers. OsSDH2-1 protein was targeted to mitochondria. Furthermore, reactive oxygen species (ROS), mainly H2O2, was excessively accumulated in leaves and young panicles of lps1, which could cause premature leaf senescence and affect panicle development and pollen function. Taken together, OsSDH2-1 plays a crucial role in leaf senescence and yield formation in rice.

OsPOP5, a prolyl oligopeptidase family gene from rice confers abiotic stress tolerance in Escherichia coli.

The prolyl oligopeptidase family, which is a group of serine peptidases, can hydrolyze peptides smaller than 30 residues. The prolyl oligopeptidase family in plants includes four members, which are prolyl oligopeptidase (POP, EC3.4.21.26), dipeptidyl peptidase IV (DPPIV, EC3.4.14.5), oligopeptidase B (OPB, EC3.4.21.83), and acylaminoacyl peptidase (ACPH, EC3.4.19.1). POP is found in human and rat, and plays important roles in multiple biological processes, such as protein secretion, maturation and degradation of peptide hormones, and neuropathies, signal transduction and memory and learning. However, the function of POP is unclear in plants. In order to study POP function in plants, we cloned the cDNA of the OsPOP5 gene from rice by nested-PCR. Sequence analysis showed that the cDNA encodes a protein of 596 amino acid residues with Mw ≈ 67.29 kD. In order to analyze the protein function under different abiotic stresses, OsPOP5 was expressed in Escherichia coli. OsPOP5 protein enhanced the tolerance of E. coli to high salinity, high temperature and simulated drought. The results indicate that OsPOP5 is a stress-related gene in rice and it may play an important role in plant tolerance to abiotic stress.

[Characterisation of a rice dwarf and twist leaf 1 (dtl1) mutant and fine mapping of DTL1 gene].

Plant height is one of the most important agronomic traits, which determines grain yield. By a largescale screening of our mutant population, we identified a dwarf with twisty leaf mutant (dwarf and twist leaf 1, dtl1). Besides dwarf with twisty leaf, dtl1 also showed reduced tiller number and sterile phenotypes. Based on the internode length of dtl1, this mutant belongs to the nl type of dwarfing phenotype. Physiological assay with two phytohormones, gibberellin (GA), and brassinosteroid (BR), suggested that dtl1 was neither deficient nor insensitive to GA and BR. Genetic analysis showed that the phenotype of dtl1 was controlled by a single recessive gene. Using F2 population derived from a cross between dtl1 and an indica cultivar Taichung Native 1, the DTL1 gene was narrowed down to a 70.4 kb between two SSR markers, RM25923 and RM6673, on the long arm of chromosome 10, and co-segregated with InDel marker Z10-29, where thirteen open reading frames were predicted without known gene involved in controlling plant height. Thus, the DTL1 gene might be a novel gene which is related to plant height in rice.

Cu-Catalyzed carbon-heteroatom coupling reactions under mild conditions promoted by resin-bound organic ionic bases.

Resin-bound organic ionic bases (RBOIBs) were developed in which tetraalkyl-ammonium or phosphonium cations are covalently attached to solid resins. The application tests showed that the performance of the tetraalkyl-ammonium-type RBOIBs is slightly better than that of the corresponding Cs salts in Cu-catalyzed C-N cross-couplings, while the tetraalkylphosphonium-type RBOIBs are significantly better than all the inorganic bases. With these newly developed RBOIBs, room-temperature Cu-catalyzed C-N coupling with various nonactivated aryl iodides and even aryl bromides can be readily accomplished. Moreover, RBOIBs can be easily recycled and reused for a number of times without much drop of activity. The good performances of RBOIBs are proposed to arise from the relatively weak binding forces between the cationic polymer backbone and basic anions, as opposed to the strong metal-anion interactions in the inorganic bases. Further applications of RBOIBs in Ni-catalyzed Suzuki-type couplings at room temperature, Cu-catalyzed C-N couplings at -30 °C, a Pd-catalyzed Heck reaction at 60 °C, and Cu-catalyzed C-S couplings at room temperature demonstrate that RBOIBs are generally applicable bases with improved performance for many other types of organic transformations.

[An overview of flowering transition in higher plants].

In higher plant, flowering transition represents a crucial transition from the vegetative stage to the reproductive stage in life cycle. This process is controlled by both endogenous and environmental factors. In Arabidopsis thaliana, four pathways, photoperiod pathway, vernalization pathway, autonomous pathway, and GA pathway were involved in flowering control. These flowering transition pathways are shown to be highly conserved in Arabidopsis and other higher plants including rice (Oryza sativa L.). This review summarizes recent progresses on flowering time control.

[Progress in the study on DREB transcription factor].

DREB transcription factor is a dehydration responsive element (DRE) binding protein. It can specifically interact with the dehydration-responsive element/C-repeat (DRE/CRT) cis-acting element contained in the promoter region of many stress-inducible genes, and can therefore control the expression of many stress-inducible genes in plant and increase strong tolerance to drought, low temperature and high salt. In this paper we described the relation between DREB transcription factor and DRE/CRT cis-acting element, the functional and structural character, and expression and regulation of DREB. We also briefly introduced the progress of research on DREB gene cloning and identification. DREB transcription factor plays an important role in the expression of many stress-inducible genes in plant, so it thus shows a very broad application future in aspect of increasing strong tolerance to stress. At the same time, we described the DREB complexity in signal transduction and the mechanism for action and expression of gene.

[Progress in regulation of rice Wx gene expression].

The granule-bound starch synthase(GBSS) is encoded by the rice Wx gene, which is the major gene for control of amylase synthesis of. This paper briefly introduced the progress in regulation of rice Wx gene expression at transcriptional level and post-transcriptional level. At the same time the influence of transgene, genetic background and temperature condition on Wx gene expression in rice was discussed. Finally some urgent questions were suggested for the further study on regulation of rice Wx gene expression.

[Arabidopsis CBF1 in plant tolerance to low temperature and drought stresses].

Since it was established that the alteration in gene expression occur during cold acclimation, a major goal in cold acclimation research has been to identify cold-responsive genes and to determine whether they play roles in freezing tolerance. Many cold-regulated genes (COR) were isolated and characterized in Arabidopsis and other cold tolerant plant species. Studies on regulation of COR in Arabidopsis have resulted in the discovery of a family of transcriptional activators, of which, CBF1, a member of the gene family, controls expression of a battery of COR in Arabidopsis and other cold tolerant plant species. During recent years, CBF-like genes were found in the genomes of chilling-sensitive plant species such as tomato and maize. Over-expression of Arabidopsis CBF1 confers elevated tolerance to chilling and drought stresses in transgenic tomato. These results promote our effort to identify and characterize CBF-like genes to improve tolerance of chilling-sensitive plant species to chilling and drought stresses.