Integration of banana streak badnavirus into the Musa genome: molecular and cytogenetic evidence. (1/30)

Breeding and tissue culture of certain cultivars of bananas (Musa) have led to high levels of banana streak badnavirus (BSV) infection in progeny from symptomless parents. BSV DNA hybridized to genomic DNA of one such parent, Obino l'Ewai, suggesting integration of viral sequences. Sequencing of clones of Obino l'Ewai genomic DNA revealed an interface between BSV and Musa sequences and a complex BSV integrant. In situ hybridization revealed two different BSV sequence locations in Obino l'Ewai chromosomes and a complex arrangement of BSV and Musa sequences was shown by probing stretched DNA fibers. This is the first report of integrated sequences that possibly lead to a plant pararetrovirus episomal infection by a mechanism differing markedly from animal retroviral systems.  (+info)

Evidence that badnavirus infection in Musa can originate from integrated pararetroviral sequences. (2/30)

When some virus- and disease-free Musa spp. (banana and plantain) are propagated by tissue culture, the resulting plants develop infections with banana streak badnavirus (BSV), a pararetrovirus. In sharp contrast to the virion DNA recovered from natural infections, the virion DNA from tissue culture-associated infections of different Musa spp. was highly similar if not identical. Although BSV does not employ integration during the infection cycle, BSV DNA was found to be integrated into the Musa genome. While one integration consisted of a partial BSV genome, a second contained more than one complete genome that was almost identical to BSV recovered from tissue culture-derived plants. The arrangement of this integrated BSV DNA suggests that it can yield an infectious episomal genome via homologous recombination. This report documents the first instance of integrated DNA of a nonintegrating virus giving rise to an episomal viral infection and identifies tissue culture as a possible trigger for the infection, raising the question of whether similar activatable viral sequences exist in the genomes of other plants and animals.  (+info)

Anti-tumour promoter activity in Malaysian ginger rhizobia used in traditional medicine. (3/30)

Zingiberaceae rhizomes commonly used in the Malaysian traditional medicine were screened for anti-tumour promoter activity using the short-term assay of inhibition of 12-O-tetradecanoyl phorbol-13-acetate (TPA)-induced Epstein-Barr virus early antigen (EBV-EA) in Raji cells. The inhibition of TPA-induced EBV-EA was detected using the indirect immunofluorescence assay (IFA) and Western blot technique. The indirect IFA detected the expression/inhibition of EBV-EA-D (diffused EA antigen), whereas the Western blot technique detected the expression/inhibition of both EBV-EA-D and EA-R (restricted EA antigen). Seven rhizomes were found to possess inhibitory activity towards EBV activation, induced by TPA; they are: Curcuma domestica, C. xanthorrhiza, Kaempferia galanga, Zingiber cassumunar, Z. officinale, Z. officinale (red variety), and Z. zerumbet. A cytotoxicity assay was carried out to determine the toxicity of the Zingiberaceae rhizome extracts. The rhizome extracts that exhibited EBV activation inhibitory activity had no cytotoxicity effect in Raji cells. Therefore, the present study shows that several Zingiberaceae species used in Malaysian traditional medicine contain naturally occurring non-toxic compounds that inhibit the EBV activation, which, if further investigated, could contribute in the development of cancer prevention methods at the tumour-promoting stage.  (+info)

Identification of zerumbone in Zingiber zerumbet Smith as a potent inhibitor of 12-O-tetradecanoylphorbol-13-acetate-induced Epstein-Barr virus activation. (4/30)

Zerumbone was isolated from the rhizomes of Zingiber zerumbet Smith as a potent inhibitor of tumor promoter 12-O-tetradecanoylphorbol-13-acetate-induced Epstein-Barr virus activation. The IC50 value of zerumbone (0.14 microM) is noticeably lower than those of the anti-tumor promoters we have hitherto obtained. Interestingly, alpha-humulene lacking the carbonyl group at the 8-position in zerumbone was inactive (IC50 > 100 microM), while 8-hydroxy-alpha-humulune was markedly active (IC50 = 0.95 microM).  (+info)

Characterization of ethylene biosynthesis associated with ripening in banana fruit. (5/30)

We investigated the characteristics of ethylene biosynthesis associated with ripening in banana (Musa sp. [AAA group, Cavendish subgroup] cv Grand Nain) fruit. MA-ACS1 encoding 1-aminocyclopropane-1-carboxylic acid (ACC) synthase in banana fruit was the gene related to the ripening process and was inducible by exogenous ethylene. At the onset of the climacteric period in naturally ripened fruit, ethylene production increased greatly, with a sharp peak concomitant with an increase in the accumulation of MA-ACS1 mRNA, and then decreased rapidly. At the onset of ripening, the in vivo ACC oxidase activity was enhanced greatly, followed by an immediate and rapid decrease. Expression of the MA-ACO1 gene encoding banana ACC oxidase was detectable at the preclimacteric stage, increased when ripening commenced, and then remained high throughout the later ripening stage despite of a rapid reduction in the ACC oxidase activity. This discrepancy between enzyme activity and gene expression of ACC oxidase could be, at least in part, due to reduced contents of ascorbate and iron, cofactors for the enzyme, during ripening. Addition of these cofactors to the incubation medium greatly stimulated the in vivo ACC oxidase activity during late ripening stages. The results suggest that ethylene production in banana fruit is regulated by transcription of MA-ACS1 until climacteric rise and by reduction of ACC oxidase activity possibly through limited in situ availability of its cofactors once ripening has commenced, which in turn characterizes the sharp peak of ethylene production.  (+info)

Functional analysis of proteins encoded by banana bunchy top virus DNA-4 to -6. (6/30)

Green fluorescent protein (GFP)-tagging was used to determine the intracellular localization pattern of the proteins encoded by banana bunchy top virus (BBTV) DNA-3, -4 and -6. The protein encoded by BBTV DNA-4, which possesses a hydrophobic N terminus, was found to localize exclusively to the cell periphery while the proteins encoded by BBTV DNA-3 and -6 were found in both the nucleus and the cytoplasm. Co-expression of the DNA-4 protein and the proteins encoded by BBTV DNA-3 and -6 revealed that the DNA-4 protein was able to re-locate the DNA-6 protein, but not the DNA-3 protein, to the cell periphery. The 29 amino acid N-terminal hydrophobic region of the DNA-4 gene product appeared to be essential for specific localization of this protein since deletion of this region abolished its ability to localize to the cell periphery. These results indicate that BBTV may utilize a system analogous to that of the begomoviruses with the BBTV DNA-6 protein acting as a nuclear shuttle protein (NSP) while the DNA-4 protein transports the NSP-DNA complexes to the cell periphery for intercellular transport. The protein encoded by BBTV DNA-5 was found to contain an LXCXE motif and yeast two-hybrid analysis revealed that the DNA-5 protein has retinoblastoma (Rb)-binding activity. This activity was dependent on an intact LXCXE motif since specific mutations to either the C or E residue completely abolished Rb-binding activity. These results indicate that the gene product of BBTV DNA-5 is an Rb-binding-like protein and may play an important role in host-cell cycle manipulation.  (+info)

Purification, characterization and structural analysis of an abundant beta-1,3-glucanase from banana fruit. (7/30)

An abundant, catalytically active beta-1,3-endoglucanase (EC 3.2.1. 39) has been isolated from the pulp of ripe bananas. Biochemical analysis of the purified protein, molecular modelling, and molecular cloning of the corresponding gene indicate that this banana enzyme closely resembles previously characterized plant beta-glucanases with respect to its amino-acid sequence, structure and biological activity. The results described in this paper demonstrate both the occurrence of an abundant active beta-1,3-endoglucanases in fruits and also readdress the question of the possible involvement of these enzymes in the ripening and/or softening process.  (+info)

Malvidin 3-rutinoside as the pigment responsible for bract color in Curcuma alismatifolia. (8/30)

Malvidin 3-rutinoside was the only anthocyanin identified from pink bracts of Curcuma alismatifolia cultivars. The concentration of malvidin 3-rutinoside in three cultivars increased as the intensity of the pink color in the bracts increased.  (+info)

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