RESUMO

Cold stress poses significant limitations on the growth, latex yield, and ecological distribution of rubber trees (Hevea brasiliensis). The GSK3-like kinase plays a significant role in helping plants adapt to different biotic and abiotic stresses. However, the functions of GSK3-like kinase BR-INSENSITIVE 2 (BIN2) in Hevea brasiliensis remain elusive. Here, we identified HbBIN2s of Hevea brasiliensis and deciphered their roles in cold stress resistance. The transcript levels of HbBIN2s are upregulated by cold stress. In addition, HbBIN2s are present in both the nucleus and cytoplasm and have the ability to interact with the INDUCER OF CBF EXPRESSION1(HbICE1) transcription factor, a central component in cold signaling. HbBIN2 overexpression in Arabidopsis displays decreased tolerance to chilling stress with a lower survival rate and proline content but a higher level of electrolyte leakage (EL) and malondialdehyde (MDA) than wild type under cold stress. Meanwhile, HbBIN2 transgenic Arabidopsis treated with cold stress exhibits a significant increase in the accumulation of reactive oxygen species (ROS) and a decrease in the activity of antioxidant enzymes. Further investigation reveals that HbBIN2 inhibits the transcriptional activity of HbICE1, thereby attenuating the expression of C-REPEAT BINDING FACTOR (HbCBF1). Consistent with this, overexpression of HbBIN2 represses the expression of CBF pathway cold-regulated genes under cold stress. In conclusion, our findings indicate that HbBIN2 functions as a suppressor of cold stress resistance by modulating HbICE1 transcriptional activity and ROS homeostasis.

Assuntos

RESUMO

Low temperature is a key factor limiting the rubber plantation extending to high latitude area. Previous work has shown that cold-induced DNA demethylation was coordinated with the expression of cold-responsive (COR) genes in Hevea brasiliensis. In this work, reduced representation bisulphite sequencing analysis of H. brasiliensis showed that cold treatment induced global genomic DNA demethylation and altered the sequence contexts of methylated cytosines, but the levels of mCG methylation in transposable elements were slightly enhanced by cold treatment. Integrated analysis of the DNA methylome and transcriptome revealed 400 genes whose expression correlated with altered DNA methylation. DNA demethylation in the upstream region of gene seems to correlate with higher gene expression, whereas demethylation in the gene body has less association. Our results suggest that cold treatment globally change the genomic DNA methylation status of the rubber tree, which might coordinate reprogramming of the transcriptome.

RESUMO

Low temperature remarkably limits rubber tree (Hevea brasiliensis Muell. Arg.) growth, latex production, and geographical distribution, but the underlying mechanisms of Hevea brasiliensis cold stress response remain elusive. Here, we identified HbSnRK2.6 as a key component in ABA signaling functions in phytohormone abscisic acid (ABA)-regulated cold stress response in Hevea brasiliensis. Exogenous application of ABA enhances Hevea brasiliensis cold tolerance. Cold-regulated (COR) genes in the CBF pathway are upregulated by ABA. Transcript levels of all five HbSnRK2.6 members are significantly induced by cold, while HbSnRK2.6A, HbSnRK2.6B, and HbSnRK2.6C can be further activated by ABA under cold conditions. Additionally, HbSnRK2.6s are localized in the cytoplasm and nucleus, and can physically interact with HbICE2, a crucial positive regulator in the cold signaling pathway. Overexpression of HbSnRK2.6A or HbSnRK2.6B in Arabidopsis extensively enhances plant responses to ABA and expression of COR genes, leading to increased cold stress tolerance. Furthermore, HbSnRK2.6A and HbSnRK2.6B can promote transcriptional activity of HbICE2, thus, increasing the expression of HbCBF1. Taken together, we demonstrate that HbSnRK2.6s are involved in ABA-regulated cold stress response in Hevea brasiliensis by regulating transcriptional activity of HbICE2.

Assuntos

RESUMO

Aiming at revealing the arsenic (As) resistance of the endophytic Kocuria strains isolated from roots and stems of Sphaeralcea angustifolia grown at mine tailing, four strains belonging to different clades of Kocuria based upon the phylogeny of 16S rRNA genes were screened for minimum inhibitory concentration (MIC). Only the strain NE1RL3 was defined as an As-resistant bacterium with MICs of 14.4/0.0125 mM and 300/20.0 mM for As3+ and As5+, respectively, in LB/mineral media. This strain was identified as K. palustris based upon analyses of cellular chemical compositions (cellular fatty acids, isoprenoides, quinones, and sugars), patterns of carbon source, average nucleotide identity of genome and digital DNA-DNA relatedness. Six genes coding to enzymes or proteins for arsenate reduction and arsenite-bumping were detected in the genome, demonstrating that this strain is resistant to As possibly by reducing As5+ to As3+, and then bumping As3+ out of the cell. However, this estimation was not confirmed since no arsenate reduction was detected in a subsequent assay. This study reported for the first time the presence of phylogenetically distinct arsenate reductase genes in a Kocuria strain and evidenced the possible horizontal transfer of these genes among the endophytic bacteria.

Assuntos

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KEY MESSAGE: An ICE-like transcription factor mediates jasmonate-regulated cold tolerance in the rubber tree (Hevea brasiliensis), and confers cold tolerance in transgenic Arabidopsis. The rubber tree (Hevea brasiliensis) is susceptible to low temperatures, and understanding the mechanisms regulating cold stress is of great potential value for enhancing tolerance to this environmental variable. In this study, we find that treatment with exogenous methyl jasmonate (MeJA) could significantly enhance Hevea brasiliensis cold tolerance. In addition, yeast two-hybrid and bimolecular fluorescence complementation (BiFC) experiments show that JASMONATE ZIM-DOMAIN(JAZ) proteins, HbJAZ1 and HbJAZ12, key repressors of JA signaling pathway, interact with HbICE2, a novel ICE (Inducer of CBF Expression)-like protein. HbICE2 was nuclear-localised and bound to the MYC recognition (MYCR) sequence. The transcriptional activation activity of HbICE2 in yeast cells was dependent on the N-terminus, and overexpression of HbICE2 in Arabidopsis resulted in elevated tolerance to chilling stress. Furthermore, dual-luciferase transient assay reveals that HbJAZ1 and HbJAZ12 proteins inhibit the transcriptional function of HbICE2. The expression of C-repeat-binding factor (CBF) signalling pathway genes including HbCBF1, HbCBF2 and HbCOR47 were up-regulated by MeJA. Taken together, our data suggest that the new ICE-like transcription factor HbICE2 is involved in jasmonate-regulated cold tolerance in Hevea brasiliensis.

Assuntos

RESUMO

Rubber trees (Hevea brasiliensis) were successfully introduced to south China in the 1950s on a large-scale; however, due to the climate, are prone to cold injury during the winter season. Increased cold tolerance is therefore an important goal, yet the mechanism underlying rubber tree responses to cold stress remains unclear. This study carried out functional characterization of HbICE1 (Inducer of CBF Expression 1) from H. brasiliensis. A nucleic protein with typical features of ICEs, HbICE1 was able to bind to MYC recognition sites and had strong transactivation activity. HbICE1 was constitutively expressed in all tested tissues, with highest levels in the bark, and was up-regulated when subjected to various stresses including cold, dehydration, salinity and wounding. When overexpressed in Arabidopsis, 35S::HbICE1 plants showed enhanced cold resistance with increased proline content, reduced malondialdehyde (MDA) metabolism and electrolyte leakage, and decreased reactive oxygen species (ROS) accumulation. Expression of the cold responsive genes (COR15A, COR47, RD29A, and KIN1) was also significantly promoted in 35S::HbICE1 compared to wild-type plants under cold stress. Differentially expressed genes (DEGs) analysis showed that cold treatment changed genes expression profiles involved in many biological processes and phytohormones perception and transduction. Ethylene, JA, ABA, as well as ICE-CBF signaling pathways might work synergistically to cope with cold tolerance in rubber tree. Taken together, these findings suggest that HbICE1 is a member of the ICE gene family and a positive regulator of cold tolerance in H. brasiliensis.

RESUMO

A comprehensive search of PubMed and Embase was performed in January 2015 to examine the available literature on validated diagnostic models of the pre-test probability of stable coronary artery disease and to describe the characteristics of the models. Studies that were designed to develop and validate diagnostic models of pre-test probability for stable coronary artery disease were included. Data regarding baseline patient characteristics, procedural characteristics, modeling methods, metrics of model performance, risk of bias, and clinical usefulness were extracted. Ten studies involving the development of 12 models and two studies focusing on external validation were identified. Seven models were validated internally, and seven models were validated externally. Discrimination varied between studies that were validated internally (C statistic 0.66-0.81) and externally (0.49-0.87). Only one study presented reclassification indices. The majority of better performing models included sex, age, symptoms, diabetes, smoking, and hyperlipidemia as variables. Only two diagnostic models evaluated the effects on clinical decision making processes or patient outcomes. Most diagnostic models of the pre-test probability of stable coronary artery disease have had modest success, and very few present data regarding the effects of these models on clinical decision making processes or patient outcomes.

Assuntos

RESUMO

A comprehensive search of PubMed and Embase was performed in January 2015 to examine the available literature on validated diagnostic models of the pre-test probability of stable coronary artery disease and to describe the characteristics of the models. Studies that were designed to develop and validate diagnostic models of pre-test probability for stable coronary artery disease were included. Data regarding baseline patient characteristics, procedural characteristics, modeling methods, metrics of model performance, risk of bias, and clinical usefulness were extracted. Ten studies involving the development of 12 models and two studies focusing on external validation were identified. Seven models were validated internally, and seven models were validated externally. Discrimination varied between studies that were validated internally (C statistic 0.66-0.81) and externally (0.49-0.87). Only one study presented reclassification indices. The majority of better performing models included sex, age, symptoms, diabetes, smoking, and hyperlipidemia as variables. Only two diagnostic models evaluated the effects on clinical decision making processes or patient outcomes. Most diagnostic models of the pre-test probability of stable coronary artery disease have had modest success, and very few present data regarding the effects of these models on clinical decision making processes or patient outcomes.

Assuntos