CK2 promotes jasmonic acid signaling response by phosphorylating MYC2 in Arabidopsis.

Jasmonic acid (JA) signaling plays a pivotal role in plant development and defense. MYC2 is a master transcription factor in JA signaling, and was found to be phosphorylated and negatively regulated by MAP kinase and receptor-like kinase. However, the kinases that positively regulate MYC2 through phosphorylation and promote MYC2-mediated activation of JA response have not been identified. Here, we identified CK2 as a kinase that phosphorylates MYC2 and thus regulates the JA signaling. CK2 holoenzyme can interact with MYC2 using its regulatory subunits and phosphorylate MYC2 at multiple sites with its catalytic subunits. Inhibition of CK2 activity in a dominant-negative plant line, CK2mut, repressed JA response. On the other hand, increasing CK2 activity by overexpression of CKB4, a regulatory subunit gene of CK2, enhanced JA response in a MYC2-dependent manner. Substitution of the Ser and Thr residues at phosphorylation sites of MYC2 by CK2 with Ala impaired MYC2 function in activating JA response. Further investigations evidenced that CK2 facilitated the JA-induced increase of MYC2 binding to the promoters of JA-responsive genes in vivo. Our study demonstrated that CK2 plays a positive role in JA signaling, and reveals a previously undiscovered mechanism that regulates MYC2 function.

Meroterpene-Like α-Glucosidase Inhibitors Based on Biomimetic Reactions Starting from ß-Caryophyllene.

BACKGROUND: Natural meroterpenes derived from phloroglucinols and ß-caryophyllene have shown high inhibitory activity against α-glucosidase or cancer cells, however, the chemical diversity of this type of skeletons in Nature is limited. METHODS: To expand the chemical space and explore their inhibitory activities against α-glucosidase (EC 3.2.1.20), we employed ß-caryophyllene and some natural moieties (4-hydroxycoumarins, lawsone or syncarpic acid) to synthesize new types of meroterpene-like skeletons. All the products (including side products) were isolated and characterized by NMR, HR-MS, and ECD. RESULTS: In total, 17 products (representing seven scaffolds) were generated through a one-pot procedure. Most products (12 compounds) showed more potential activity (IC50 < 25 µM) than the positive controls (acarbose and genistein, IC50 58.19, and 54.74 µM, respectively). Compound 7 exhibited the most potent inhibition of α-glucosidase (IC50 3.56 µM) in a mixed-type manner. The CD analysis indicated that compound 7 could bind to α-glucosidase and influence the enzyme's secondary structure. CONCLUSIONS: Compound 7 could serve as a new type of template compound to develop α-glucosidase inhibitors. Full investigation of a biomimic reaction can be used as a concise strategy to explore diverse natural-like skeletons and search for novel lead compounds.

Meroterpene-like compounds derived from ß-caryophyllene as potent α-glucosidase inhibitors.

Meroterpenoids isolated from guava (Psidium guajava) and Rhodomyrtus tomentosa possess special skeletons which incorporate terpenoids with phloroglucinol derivatives. Most of these meroterpenoids showed high cytotoxicity against cancer cell lines. However, their chemical diversity is very limited. Herein, we employed a biomimetic hetero-cycloaddition starting from ortho-quinone methides and an abundant natural product, ß-caryophyllene, to generate meroterpene-like compounds. Considering that the source plant has hyperglycemic functions, α-glucosidase was selected as a target for bioassay. Nine compounds were screened out for promising activities (IC50 < 15 µM), which were better than the positive controls genistein and acarbose. The best inhibitor 12 (IC50 2.73 µM) possesses two caryophyllene moieties. They represented a new type of skeleton possessing activities against α-glucosidase. The kinetic study exhibited that these inhibitors belong to a non-competitive type. All these inhibitors may provide an opportunity to develop a new class of antidiabetic agents.

The association of CYP1A1 genetic polymorphisms and additional gene-gene interaction with ischemic stroke in the eastern Han of China.

The aim of this study was to investigate the association between CYP1A1 gene polymorphism and ischaemic stroke (IS) risk, and the impact of gene-gene interaction on IS risk based on a Chinese Han case-control study. A total of 1162 subjects (612 men and 550 women), with a mean age of 63.1 ± 12.5 years old, were selected, including 580 IS patients and 582 normal controls. Logistic regression was performed to investigate association between single-nucleotide polymorphisms (SNP) and IS risk, and generalized multifactor dimensionality reduction (GMDR) was used to analyze the gene-gene interaction. Logistic regression analysis showed that the frequency for rs4646903 minor alleles was lower in cases than that in normal controls, and C allele of rs4646903 was 20.7 % in ischemic stroke cases and 27.1 % in controls subjects (p < 0.001). Logistic analysis showed the significant association between genotypes of variants in rs4646903 and decreased ischemic stroke risk. GMDR analysis indicated that there was a significant two-locus model (p = 0.0107) involving rs4646903 and rs1048943, indicating a potential gene-gene interaction between rs4646903 and rs1048943. Overall, the two- locus models had a cross-validation consistency of 9 of 10, and had the testing accuracy of 60.72 %. Subjects with TC or CC of rs4646903 and AG or GG of rs1048943 genotype have lowest ischemic stroke risk, compared to subjects with TT of rs4646903 and AA of rs1048943 genotype, and OR (95 % CI) was 0.63 (0.42-0.89). rs4646903 minor alleles and interaction between rs4646903 and rs1048943 were associated with decreased IS risk.

TIME FOR COFFEE controls root meristem size by changes in auxin accumulation in Arabidopsis.

Roots play important roles in plant survival and productivity as they not only anchor the plants in the soil but are also the primary organ for the uptake of nutrients from the outside. The growth and development of roots depend on the specification and maintenance of the root meristem. Here, we report a previously unknown role of TIME FOR COFFEE (TIC) in controlling root meristem size in Arabidopsis. The results showed that loss of function of TIC reduced root meristem length and cell number by decreasing the competence of meristematic cells to divide. This was due to the repressed expression of PIN genes for decreased acropetal auxin transport in tic-2, leading to low auxin accumulation in the roots responsible for reduced root meristem, which was verified by exogenous application of indole-3-acetic acid. Downregulated expression of PLETHORA1 (PLT1) and PLT2, key transcription factors in mediating the patterning of the root stem cell niche, was also assayed in tic-2. Similar results were obtained with tic-2 and wild-type plants at either dawn or dusk. We also suggested that the MYC2-mediated jasmonic acid signalling pathway may not be involved in the regulation of TIC in controlling the root meristem. Taken together, these results suggest that TIC functions in an auxin-PLTs loop for maintenance of post-embryonic root meristem.

A gain-of-function mutation in IAA8 alters Arabidopsis floral organ development by change of jasmonic acid level.

Auxin regulates a variety of physiological processes via its downstream factors included Aux/IAAs. In this study, one of these Aux/IAAs, IAA8 is shown to play its role in Arabidopsis development with transgenic plants expressing GFP-mIAA8 under the control of IAA8 promoter, in which IAA8 protein was mutated by changing Pro170 to Leu170 in its conserved domain II. These transgenic dwarfed plants had more lateral branches, short primary inflorescence stems, decreased shoot apical dominance, curled leaves and abnormal flower organs (short petal and stamen, and bent stigmas). Further experiments revealed that IAA8::GFP-mIAA8 plants functioned as gain-of-function mutation to increase GFP-mIAA8 amount probably by stabilizing IAA8 protein against proteasome-mediated protein degradation with IAA8::GFP-IAA8 plants as control. The searching for its downstream factors indicated its interaction with both ARF6 and ARF8, suggesting that IAA8 may involve in flower organ development. This was further evidenced by analyzing the expression of jasmonic acid (JA) biosynthetic genes and JA levels because ARF6 and ARF8 are required for normal JA production. These results indicated that in IAA8::GFP-mIAA8 plants, JA biosynthetic genes including DAD1 (AT2G44810), AOS (AT5G42650) and ORP3 (AT2G06050) were dramatically down-regulated and JA level in the flowers was reduced to 70 % of that in wild-type. Furthermore, exogenous JA application can partially rescue short petal and stamen observed IAA8::GFP-mIAA8 plants. Thus, IAA8 plays its role in floral organ development by changes in JA levels probably via its interaction with ARF6/8 proteins.

Fabricating biodegradable calcium phosphate/calcium sulfate cement reinforced with cellulose: in vitro and in vivo studies.

Osteoporosis is a growing public health concern worldwide. To avoid extra surgeries, developing biodegradable bone cement is critical for the treatment of osteoporosis. Herein, we designed calcium phosphate/calcium sulfate cement reinforced with sodium carboxymethyl cellulose (CMC/OPC). It presents an appropriate physicochemical performance for clinical handling. Meanwhile, CMC/OPC bone cement promotes osteogenic differentiation in vitro. Results of the immune response in vitro and in vivo confirmed that increasing the cellulose content triggered macrophage switching into the M2 phenotype and CMC/OPC exhibited significant anti-inflammation. Furthermore, in vitro and in vivo degradation demonstrated that cellulose tailors the degradation rate of composite bone cement, which achieved a linear degradation process and could degrade by more than 90% for 12 weeks. In summary, the composite bone cement CMC/OPC is a promising candidate for bone repair applications.

Functional comparison of catalase genes in the elimination of photorespiratory H2O2 using promoter- and 3'-untranslated region exchange experiments in the Arabidopsis cat2 photorespiratory mutant.

Photorespiration-associated production of H(2) O(2) accounts for the majority of total H(2) O(2) in leaves of C(3) plants and is mainly eliminated by catalases. In Arabidopsis, lack of CAT2, but not CAT1 or CAT3, results in growth suppression and a marked accumulation of H(2) O(2) in leaves. To evaluate the contribution of individual catalase genes and their promoters to catalase function, we investigated the growth suppression and H(2) O(2) accumulation phenotypes of Arabidopsis derivatives expressing catalase genes from heterologous CAT promoters in a cat2 mutant background. The expression of CAT2 from the CAT2 promoter restored the wild-type phenotype in a cat2-1 mutant, while CAT1 and CAT3 promoter-driven expression of CAT2 did not. Ectopic expression of CAT3 from the CAT2 promoter also restored the normal phenotype, unlike that of CAT1 which required replacement of the CAT1 3'-untranslated region (UTR) with that of CAT2. These results demonstrated that the photorespiratory role of CAT2 is determined mainly by the regulation of its promoter activity. The 3'-UTR of CAT2 was vital for controlling CAT2 protein levels under photorespiratory conditions. Identification of component of heterotetramers catalase isoforms suggested that there is some functional redundancy between CAT2 and CAT1 and CAT3.

Convergent genomic signatures of high-altitude adaptation among domestic mammals.

Abundant and diverse domestic mammals living on the Tibetan Plateau provide useful materials for investigating adaptive evolution and genetic convergence. Here, we used 327 genomes from horses, sheep, goats, cattle, pigs and dogs living at both high and low altitudes, including 73 genomes generated for this study, to disentangle the genetic mechanisms underlying local adaptation of domestic mammals. Although molecular convergence is comparatively rare at the DNA sequence level, we found convergent signature of positive selection at the gene level, particularly the EPAS1 gene in these Tibetan domestic mammals. We also reported a potential function in response to hypoxia for the gene C10orf67, which underwent positive selection in three of the domestic mammals. Our data provide an insight into adaptive evolution of high-altitude domestic mammals, and should facilitate the search for additional novel genes involved in the hypoxia response pathway.

The disturbance of small RNA pathways enhanced abscisic acid response and multiple stress responses in Arabidopsis.

The phytohormone abscisic acid (ABA) regulates plant growth and development as well as stress tolerance. To gain more insights into ABA signalling, a population of chemical-inducible activation-tagged Arabidopsis mutants was screened on the basis of the ABA effect on the inhibition of seed germination. Two novel ABA supersensitive mutants ABA supersensitive during germination1 (absg1) and absg2 were characterized as alleles of Dicer-like1 (DCL1) and HEN1, respectively, as microRNA biogenesis genes, and accordingly, these two mutants were renamed dcl1-11 and hen1-16. The dcl1-11 mutant was an ABA hypersensitive mutant for seed germination and root growth. Reverse transcriptase polymerase chain reaction assays revealed that the expression of ABA- and stress-responsive genes was increased in dcl1-11, as compared with the wild type (WT). Furthermore, the germination assay showed that dcl1-11 was also more sensitive to salt and osmotic stress. The hen1-16 mutant also showed supersensitive to ABA during seed germination. Further analysis showed that, among the microRNA biogenesis genes, all the other mutants were not only enhanced in sensitivity to ABA, salt and osmotic stress, but also enhanced the expression of ABA-responsive genes. In addition to the mutants in the microRNA biogenesis, the interruption of the production of crucial components of other small RNA pathways such as dcl2, dcl3 and dcl4 also caused ABA supersensitive during germination.

Perturbation of auxin homeostasis by overexpression of wild-type IAA15 results in impaired stem cell differentiation and gravitropism in roots.

Aux/IAAs interact with auxin response factors (ARFs) to repress their transcriptional activity in the auxin signaling pathway. Previous studies have focused on gain-of-function mutations of domain II and little is known about whether the expression level of wild-type Aux/IAAs can modulate auxin homeostasis. Here we examined the perturbation of auxin homeostasis by ectopic expression of wild-type IAA15. Root gravitropism and stem cell differentiation were also analyzed. The transgenic lines were less sensitive to exogenous auxin and exhibited low-auxin phenotypes including failures in gravity response and defects in stem cell differentiation. Overexpression lines also showed an increase in auxin concentration and reduced polar auxin transport. These results demonstrate that an alteration in the expression of wild-type IAA15 can disrupt auxin homeostasis.

Genetic differentiations between randomly and selectively bred pig populations in Yunnan, China.

To assess the genetic diversity between randomly and selectively bred populations, we sequenced 438 bp of the mitochondrial DNA control region from 102 pigs. These samples represented four native pig breeds, one nucleus and one conservation herd from Yunnan, China. Twenty haplotypes with sixteen polymorphic sites were identified. The number of haplotypes in the nucleus herd of Saba pig and the conservation herd of Banna miniature pig were restricted to three and one, respectively, while the randomly bred pig populations exhibited over six haplotypes. Notably, haplotype diversity in randomly bred populations was significantly greater than the selectively bred populations (h=0.732 vs. 0.425 and 0, exact test, P<=0.0036). These findings demonstrate that selective breeding generated low genetic diversity compared to randomly bred pig breeds. A timely intervention and well programmed breeding approach would stop further genetic diversity reduction in the nucleus and conservation herds of native pig breeds. Otherwise, selective breeding would dramatically reduce genetic diversity in only several years, indicating that sharp contradictions exist between breeding, conservation and genetic diversity. Genetic relationships are discussed based on net genetic distances among pig populations.

Identification of microRNAs from rice.

MicroRNAs (miRNAs) are important regulators in the development of plants and animals. Several hundred have been identified from animals, and about a dozen have been cloned from plants, mainly Arabidopsis thaliana (L.) Heynh. We have identified nine miRNAs in Oryza sativa L., an important food crop that has been sequenced in recent years. The nine miRNAs include miRNA171 and miRNA167, which were also identified in Arabidopsis. These had the typical properties of miRNAs, including short length, an ability to form a stem-loop structure with a flanking genomic sequence and they could be identified by northern blot analyses. In addition, m-fold program and computational analyses indicted that the potential targets of six of the nine miRNAs are four known gene families and two unknown protein families, which comprise 16 unique genes.