Synthesis,Structural and Antioxidant Studies of Some Novel N-Ethyl Phthalimide Esters

A series of N-ethyl phthalimide esters 4(a-n) were synthesized and characterized by spectroscopic studies. Further, the molecular structure of majority of compounds were analysed by single crystal X-ray diffraction studies. The X-ray analysis revealed the importance of substituents on the crystal stability and molecular packing. All the synthesized compounds were tested for in vitro antioxidant activity by DPPH radical scavenging, FRAP and CUPRAC methods. Few of them have shown good antioxidant activity.     

Structure of the glucanase inhibitor protein (GIP) family from phytophthora species suggests coevolution with plant endo-beta-1,3-glucanases

During invasion of their plant hosts, species of the oomycete genus Phytophthora secrete glucanase inhibitor proteins (GIPs) into the plant apoplast, which bind and inhibit the activity of plant extracellular endo-beta-1,3-glucanases (EGases). GIPs show structural homology to the chymotrypsin class of serine proteases (SP) but lack proteolytic activity due to the absence of an intact catalytic triad and, thus, belong to a broader class of proteins called serine protease homologs (SPH). To study the evolutionary relationship between GIPs and functional SP, database searches were used to identify 48 GIP homologs in the P. sojae, P. ramorum, and P. infestans genomes, composing GIPs, SPH, and potentially functional SP. Analyses of P. infestans-inoculated tomato leaves showed that P. infestans GIPs and tomato EGases are present in the apoplast and form stable complexes in planta. Studies of the temporal expression of a four-membered GIP family from P. infestans (PiGIP1 to PiGIP4) further revealed that the genes show distinctly different patterns during an infection timecourse. Codon evolution analyses of GIP homologs identified several positively selected peptide sites and structural modeling revealed them to be in close proximity to rapidly evolving EGase residues, suggesting that the interaction between GIPs and EGases has the hallmarks of a coevolving molecular arms race.     

GINS Inactivation Phenotypes Reveal Two Pathways for Chromatin Association of Replicative α and ε DNA Polymerases in Fission Yeast

The tetrameric GINS complex, consisting of Sld5-Psf1-Psf2-Psf3, plays an essential role in the initiation and elongation steps of eukaryotic DNA replication, although its biochemical function is unclear. Here we investigate the function of GINS in fission yeast, using fusion of Psf1 and Psf2 subunits to a steroid hormone-binding domain (HBD) to make GINS function conditional on the presence of β-estradiol. We show that inactivation of Psf1-HBD causes a tight but rapidly reversible DNA replication arrest phenotype. Inactivation of Psf2-HBD similarly blocks premeiotic DNA replication and leads to loss of nuclear localization of another GINS subunit, Psf3. Inactivation of GINS has distinct effects on the replication origin association and chromatin binding of two of the replicative DNA polymerases. Inactivation of Psf1 leads to loss of chromatin binding of DNA polymerase ε, and Cdc45 is similarly affected. In contrast, chromatin association of the catalytic subunit of DNA polymerase α is not affected by defective GINS function. We suggest that GINS functions in a pathway that involves Cdc45 and is necessary for DNA polymerase ε chromatin binding, but that a separate pathway sets up the chromatin association of DNA polymerase α.     

Mesozoic origin and ‘out-of-India’ radiation of ricefishes (Adrianichthyidae)

The Indian subcontinent has an origin geologically different from Eurasia, but many terrestrial animal and plant species on it have congeneric or sister species in other parts of Asia, especially in the Southeast. This faunal and floral similarity between India and Southeast Asia is explained by either of the two biogeographic scenarios, ‘into-India’ or ‘out-of-India’. Phylogenies based on complete mitochondrial genomes and five nuclear genes were undertaken for ricefishes (Adrianichthyidae) to examine which of these two biogeographic scenarios fits better. We found that Oryzias setnai, the only adrianichthyid distributed in and endemic to the Western Ghats, a mountain range running parallel to the western coast of the Indian subcontinent, is sister to all other adrianichthyids from eastern India and Southeast–East Asia. Divergence time estimates and ancestral area reconstructions reveal that this western Indian species diverged in the late Mesozoic during the northward drift of the Indian subcontinent. These findings indicate that adrianichthyids dispersed eastward ‘out-of-India’ after the collision of the Indian subcontinent with Eurasia, and subsequently diversified in Southeast–East Asia. A review of geographic distributions of ‘out-of-India’ taxa reveals that they may have largely fuelled or modified the biodiversity of Eurasia.     

Independent evolution of a new allele of F<Subscript>1</Subscript> pollen sterility gene <Emphasis Type="Italic">S27</Emphasis> encoding mitochondrial ribosomal protein L27 in <Emphasis Type="Italic">Oryza nivara</Emphasis>

Loss of function of duplicated genes plays an important role in the evolution of postzygotic reproductive isolation. The widespread occurrence of gene duplication followed by rapid loss of function of some of the duplicate gene copies suggests the independent evolution of loss-of-function alleles of duplicate genes in divergent lineages of speciation. Here, we found a novel loss-of-function allele of S27 in the Asian annual wild species Oryza nivara, designated S27-niv ^s , that leads to F₁ pollen sterility in a cross between O. sativa and O. nivara. Genetic linkage analysis and complementation analysis demonstrated that S27-niv ^s lies at the same locus as the previously identified S27 locus and S27-niv ^s is a loss-of-function allele of S27. S27-niv ^s is composed of two tandem mitochondrial ribosomal protein L27 genes (mtRPL27a and mtRPL27b), both of which are inactive. The coding and promoter regions of S27-niv ^s showed a number of nucleotide differences from the functional S27-T65 ⁺ allele. The structure of S27-niv ^s is different from that of a previously identified null S27 allele, S27-glum ^s , in the South American wild rice species O. glumaepatula, in which mtRPL27a and mtRPL27b are absent. These results show that the mechanisms for loss-of-function of S27-niv ^s and S27-glum ^s are different. Our results provide experimental evidence that different types of loss-of-function alleles are distributed in geographically and phylogenetically isolated species and represent a potential mechanism for postzygotic isolation in divergent species.     

Single Nucleus Genome Sequencing Reveals High Similarity among Nuclei of an Endomycorrhizal Fungus

Nuclei of arbuscular endomycorrhizal fungi have been described as highly diverse due to their asexual nature and absence of a single cell stage with only one nucleus. This has raised fundamental questions concerning speciation, selection and transmission of the genetic make-up to next generations. Although this concept has become textbook knowledge, it is only based on studying a few loci, including 45S rDNA. To provide a more comprehensive insight into the genetic makeup of arbuscular endomycorrhizal fungi, we applied de novo genome sequencing of individual nuclei of Rhizophagus irregularis. This revealed a surprisingly low level of polymorphism between nuclei. In contrast, within a nucleus, the 45S rDNA repeat unit turned out to be highly diverged. This finding demystifies a long-lasting hypothesis on the complex genetic makeup of arbuscular endomycorrhizal fungi. Subsequent genome assembly resulted in the first draft reference genome sequence of an arbuscular endomycorrhizal fungus. Its length is 141 Mbps, representing over 27,000 protein-coding gene models. We used the genomic sequence to reinvestigate the phylogenetic relationships of Rhizophagus irregularis with other fungal phyla. This unambiguously demonstrated that Glomeromycota are more closely related to Mucoromycotina than to its postulated sister Dikarya.