Fsr1, a striatin homologue,forms an endomembrane‐associated complex that regulates virulence in the maize pathogen Fusarium verticillioides

Fsr1, a homologue of mammalian striatin, containing multiple protein‐binding domains and a coiled‐coil (CC) domain, is critical for Fusarium verticillioides virulence. In mammals, striatin interacts with multiple proteins to form a STRIPAK (striatin‐interacting phosphatase and kinase) complex that regulates a variety of developmental processes and cellular mechanisms. In this study, we identified the homologue of a key mammalian STRIPAK component STRIP1/2 (striatin‐interacting proteins 1 and 2) in F. verticillioides, FvStp1, which interacts with Fsr1 in vivo. Gene deletion analysis indicates that FvStp1 is critical for F. verticillioides stalk rot virulence. In addition, we identified three proteins, designated FvCyp1, FvScp1 and FvSel1, which interact with the Fsr1 CC domain via a yeast two‐hybrid screen. Importantly, FvCyp1, FvScp1 and FvSel1 co‐localize to endomembrane structures, each having a preferred localization in the cell, and they are all required for F. verticillioides stalk rot virulence. Moreover, these proteins are necessary for the correct localization of Fsr1 to the endoplasmic reticulum (ER) and nuclear envelope. Thus, we identified several novel components in the STRIPAK complex that regulates F. verticillioides virulence, and propose that the correct organization and localization of Fsr1 are critical for STRIPAK complex function.     

Freeze-etch appearance of the tight junctions in the epithelium of small and large intestine of mice

Summary The ultrastructure of the central layer and the contributing plasma membranes of tight junctions has been studied in epithelia of the jejunum and colon of mice.Examination of freeze-etched plasma membranes of epithelial cells has revealed that they consist of a central layer, with fracturing characteristics similar to bimolecular lipid leaflets, which is covered on both sides with a layer of particles.The fusion of the outer membrane surfaces of adjacent cells in the region of the tight junction leads to the formation of a new common structure consisting of a meshwork of fibrils embedded in a matrix substance. The fibrils probably contain protein. They have a diameter of 65 ± 10 Å and are linked together so that they form around the distal end of each cell a continuous belt-like meshwork which is extended proximally at the joints where three cells meet. As the fibrillar mesh appears to be strongly attached to the central lipid layer of the two adjoining membranes, in contrast to the weakly bound surrounding matrix, it is believed that the fibrils forming the continuous meshwork could be the mechanical coupling and the sealing elements of the tight junction. Their arrangement in the form of a concertinalike mesh would make the whole structure very flexible. In the region of the junction the membranes are constricted along the lines of attachment to the fibrils and bulge outwards,i.e. towards the cytoplasm, in the areas of the matrix material. In the resulting grooves on the cytoplasmic side of the plasma membranes regularly spaced particles with a diameter of 90 ± 10 Å can be detected. Various observations suggest that these particles could be connected through the central layer of the membranes to the fibrils on the other side. This would offer a possible explanation for the known abhesion properties of tight junctions. The described structures are also evaluated in terms of current theories of cell communication.     

Genetic variation within and relationships among populations of Asian water buffalo (Bubalus bubalis)

Genetic variation at 53 protein-coding loci (25 polymorphic) was analysed for 17 water buffalo populations – 12 swamp, three Lankan and two of the Murrah breed (river type), to determine the magnitude of genetic differentiation and the genetic relationships among the populations. In accord with previous cytological studies, the Lankan buffalo clearly are river type. Significant deviations from Hardy–Weinberg equilibrium were shown for a number of locus–population combinations, with all populations but one showing significant heterogeneity in these deviations among loci. By contrast, heterogeneity among populations for each locus was much less, indicating locus-specific deviations, which suggest selection affecting allele frequencies at some loci. There was significant genetic differentiation among populations of both the swamp and river types. The differentiation among the swamp populations may reflect the geography of south-east Asia and the presumed spread of the swamp buffalo through this region. Phylogenies derived from pairwise genetic distance estimates show the clear separation of swamp and river types, but the topology of the swamp populations shows rather poor consistency with their geographic locations. For at least one population (Australia), it is clear that bottleneck effects have distorted the phylogenetic topology. Average genetic distances for both the swamp and river types, as compared with previous studies of livestock breeds, show that the genetic differentiation of each of these sets of populations is of the same order of magnitude as that among well-recognized and established breeds of other species.     

Effect of temperature on antagonistic and biocontrol potential of shape Trichoderma sp. on Sclerotium rolfsii

Sclerotium rolfsii is a destructive soil-borne and postharvest plant pathogen. Use of the antagonistic fungus Trichoderma sp. has been earlier reported by us to successfully control this pathogen under postharvest conditions. In the present paper we report on the effects of temperature on the growth and biocontrol potential of Trichoderma sp. on S. rolfsii. Experimental results indicated that S. rolfsii and Trichoderma sp. have different temperature optima for growth: 30–35 °C for the pathogen and 25–30 °C for the antagonist. In dual culture, Trichoderma overgrew S. rolfsii at 25 °C and 30 °C, but at 35 °C and 37 °C, S. rolfsii overgrew the colony of Trichoderma. Trichoderma produced higher concentration of fungitoxic metabolites in broth culture at higher temperatures. In bioassays using ginger slices and whole rhizomes, it has been demonstrated that Trichoderma is not very effective in suppressing S. rolfsii at temperatures above 30 °C. In light of these results, possible mechanisms of biocontrol of S. rolfsii as a postharvest pathogen has been discussed. Storage temperature has been suggested as a critical factor in biocontrol of S. rolfsii. This revised version was published online in June 2006 with corrections to the Cover Date.     

Expression of cryIA(c) gene of Bacillus thuringiensis in transgenic chickpea plants inhibits development of pod-borer (Heliothis armigera) larvae

Two strains of chickpea (Cicer arietinum L.) ICCV-1 and ICCV-6, were used for transgenic plant generation. Embryo axis of mature seed devoid of the root meristem and the shoot apex was used as experimental material. The explants were cultured in medium containing MS macro salts, 4 × MS micro salts, B5 vitamins, 3.0 mg l–1 BAP, 0.004 mg l–1 NAA, 30 mg l–1 sucrose and cultured at 26 °C in dark, 24 h prior to bombardment. Gene delivery to the explants was carried out using a Bio-Rad Biolistic 1000/He particle gun. A chimaeric, truncated bacterial cryIA(c) gene construct was developed for plant expression with the CaMV35S promoter, nos terminator, an initiatory kozak sequence and a translational enhancer (STAR-P) sequence of tobacco mosaic virus. This cryIA(c) gene was cotransferred with a plasmid containing nptII gene as the selection marker. Transgenic kanamycin resistant chickpea plants were obtained through multiple shoot formation and repeated selection of the bombarded explants. Molecular analyses of the transformants revealed the presence of the transferred functional cryIA(c) gene in plant. Insect feeding assay indicated that the expression level of the cryIA(c) gene was inhibitory to the development of the feeding larvae of Heliothis armigera Hubner, the chickpea pod-borer     

Importance of Laccase in Vegetative Growth of Pleurotus florida

Mycelial culture of Pleurotus florida produced highest extracellular laccase in optimum growth medium. At least two laccases (L(inf1) and L(inf2)) were shown to be present in the culture filtrate. Low-laccase-yielding mutants with impaired L(inf2) activity had poor mycelial growth and could not form fruit body, whereas the revertants from the same mutants were similar to the parent in mycelial growth and fruit body formation.     

Characterization of two proteinase inhibitor (ATI) cDNAs from alfalfa leaves (Medicago sativa var. Vernema): the expression of ATI genes in response to wounding and soil microorganisms

cDNAs encoding two Bowman-Birk proteinase inhibitors were isolated from the leaves of alfalfa (Medicago sativa). The cDNAs are derived from a small gene family (3 to 10 genes) encoding alfalfa trypsin inhibitors (ATIs). Each cDNA clone encoded a mature ATI that was part of a larger, putative preprotein. ATI mRNAs are continuously expressed in flower parts, but are mechanically wound-inducible in the stems and leaves. ATI mRNA is shown to be continuously present in roots of soil-grown plants, but its presence is primarily in response to microorganisms present in the soil. Additionally, while mechanical wounding of the alfalfa roots induced ATI mRNA synthesis both in the roots and in the leaves, microbial infection of the roots triggered ATI mRNA synthesis in the roots but not in the leaves. These results suggest that both local and systemic signalling pathways for proteinase inhibitor synthesis are present in alfalfa plants.