An unusual method of development and sporulation of Colletotrichum gloeosporioides on castor leaf – an SEM account

Development and sporogenesis of Colletotrichum gloeosporioides on castor leaf differed from that on other known host plants. C. gloeosporioides had three kinds of hyphae on castor leaf: primary infection hyphae (PIH), runner hyphae (RH) and secondary infection hyphae (SIH). The PIH originated from conidia, grew on leaf surface and entered the leaf by direct penetration of the cuticle without forming appressoria. The RH were sub-cuticular hyphae, the track of which was traceable by the bulgings on the leaf surface, and the SIH were the hyphae that emerged to leaf surface from RH through the cuticle or stomata. Conidia were initiated as small protrusions along the lengths of RH and SIH that got differentiated into distinct conidia, each born on a short stumpy conidiophore without forming any congregation. The protrusions from RH emerged to the leaf surface by piercing the cuticle, and they developed into distinct conidia on the leaf surface. The conidia developed from RH and SIH were identical in size and shape. Even though conidia were occasionally found emerged through stomata, that appeared to be random than a preferred route for the discharge of conidia. The penetration and sporogenesis of C. gloeosporioides on castor leaf differed from that reported on mulberry leaf.     

The level of viral antigen presented by hepatocytes influences CD8 T-cell function

CD8 T cells exert their antiviral function through cytokines and lysis of infected cells. Because hepatocytes are susceptible to noncytolytic mechanisms of viral clearance, CD8 T-cell antiviral efficiency against hepatotropic viruses has been linked to their capacity to produce gamma interferon (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha). On the other hand, intrahepatic cytokine production triggers the recruitment of mononuclear cells, which sustain acute and chronic liver damage. Using virus-specific CD8 T cells and human hepatocytes, we analyzed the modulation of virus-specific CD8 T-cell function after recognition peptide-pulsed or virally infected hepatocytes. We observed that hepatocyte antigen presentation was generally inefficient, and the quantity of viral antigen strongly influenced CD8 T-cell antiviral function. High levels of hepatitis B virus production induced robust IFN-gamma and TNF-alpha production in virus-specific CD8 T cells, while limiting amounts of viral antigen, both in hepatocyte-like cells and naturally infected human hepatocytes, preferentially stimulated CD8 T-cell degranulation. Our data document a mechanism where virus-specific CD8 T-cell function is influenced by the quantity of virus produced within hepatocytes.     

Genetic transformation of <Emphasis Type="Italic">Gentiana macrophylla</Emphasis> with <Emphasis Type="Italic">Agrobacterium rhizogenes</Emphasis>: growth and production of secoiridoid glucoside gentiopicroside in transformed hairy root cultures

Hairy root cultures of Gentiana macrophylla were established by infecting the different explants four Agrobacterium rhizogenes strains namely A₄GUS, R1000, LBA 9402 and ATCC11325, and hairy root lines were established with A. rhizogenes strain R1000 in 1/2 MS + B₅ medium. Initially, 42 independent hairy root clones were maintained and seven clones belongs to different category were evaluated for growth, morphology, integration and expression of Ri T-DNA genes, and alkaloid contents in dry root samples. On the basis of total root elongation, lateral root density and biomass accumulation on solid media, hairy root clones were separated into three categories. PCR and Southern hybridization analysis revealed both left and right T-DNA integration in the root clones and RT-PCR analysis confirmed the expression of hairy root inducible gene. GUS assay was also performed to confirm the integration of left T-DNA. The accumulation of considerable amounts of the root-specific secoiridoid glucosides gentiopicroside was observed in GM1 ( and ) and the GM2 ( and DNA) type clones in considerably higher amount whether as two but callus-type clones (GM3) accumulated much less or only very negligible amounts of gentiopicroside. Out of four media composition the 1/2 MS + B₅ vitamin media was found most suitable. We found that initial establishment of root cultures largely depends on root:media ratio. Maximum growth rate was recorded in 1:50 root:media ratio. The maximum biomass in terms of fresh weight (33-fold) was achieved in 1/2 MS + B₅ media composition after 35 days in comparison to sixfold increase in control. The biomass increase was most abundant maximum from 15 to 30 days. Influence of A. rhizogenes strains and Ri plasmid of hairy root induction, the possible role of the T_L-DNA and T_R-DNA genes on growth pattern of hairy root, initial root inoculum:media ratio and effect of media composition is discussed.     

Chiral and achiral macrocyclic copper(II) complexes: Synthesis, characterization, and comparative binding studies with calf-thymus DNA

The new chiral macrocyclic complexes [1,2-bis(1H-benzimidazol-2-yl)-1-(1,8-dihydro-1,3,5,8,10,12-hexaazacyclotetradecane)-2-hydroxyethanolate] copper(II) and -nickel(II) perchlorate, 3 and 4, respectively, were synthesized by the reaction of 1,2-bis(1H-benzimidazol-2-yl)ethane-1,2-diol (L) and (1,8-dihydro-1,3,5,8,10,12-hexaazacyclotetradecane)copper(II) and -nickel(II) diperchlorate complexes, 1 and 2, respectively. All complexes were characterized by various spectroscopic techniques. Molar-conductance measurements showed that all of the complexes are ionic in nature. In complexes 3 and 4, the metal center is encapsulated by the ligand L in a pentacoordinated environment. The optical-rotation values ([alpha](D)) of 3 and 4 at 25 degrees indicate that the complexes are chiral. Absorption- and fluorescence-spectral studies, cyclic voltammetry, and viscosity measurements have been carried out to assess the comparative binding of complexes 1 and 3 with calf thymus (CT)-DNA. Analysis of the results suggests that the new chiral complex 3 binds to CT-DNA through a partial intercalation mode that is different from the binding mode of parent achiral complex 1. The complexes 1 and 3 bind to CT-DNA with binding constants K(b) of 2.7 x 10(4) and 6.6 x 10(4) M(-1), respectively. Circular-dichroism (CD) studies have been further employed to ascertain the binding mode of complex 3, which is consistent with the other spectral studies.     

Progress and challenges in producing polyhydroxyalkanoate biopolymers from cyanobacteria

Growing concerns over conventional plastic materials and their detrimental effects on the environment have paved the way for exploring alternative sources for the production of bioplastics/biodegradable polymers. Polyhydroxyalkanoates (PHAs), being eco-friendly, biodegradable and renewable, with material properties comparable to conventional plastics, have gained significant attention for research and commercial ventures. Bacteria are reported to be the most efficient microbes in accumulating PHAs, where productivity up to 3.2 g L^?1 h^?1 can be attained. PHA production from a bacterial system, however, is found to be expensive. Cyanobacteria are now considered as prospective photoautotrophic systems with many advantages over higher plants for low-cost production of PHAs. Cyanobacteria have the potential to synthesize polyhydroxybutyrate (PHB) under photoautotrophic and chemoheterotrophic conditions using carbon substrates like glucose, acetate, and maltose, individually or in combination. Several studies have shown improvement in PHA yield in cyanobacteria by limiting nutrients and/or addition of various precursors. Under optimized conditions, PHB and P(3HB-co-3HV) co-polymer accumulation can reach up to 85 and 77% of dry cell weight (dcw) with a productivity of 13.3 and 1.6 mg L^?1 h^?1, respectively. Despite the strategic increase in the potential of PHA accumulation in cyanobacteria, the productivity does not suffice for economic production. Therefore, economically feasible production of PHA in cyanobacteria might be attained by technological improvements in various aspects like improvement in mass cultivation techniques, alternate low-cost organic substrates, use of various metabolic inhibitors to stimulate intracellular accumulation, and by suppression and overexpression of specific biosynthetic pathways by genetic engineering approaches.