The gene Osl2, which is specifically upregulated during leaf senescence in rice (Oryza sativa L. cv. Tainong 67), was cloned and functionally characterized. The protein coding region of the gene consists of 19 exons encoding 516 amino acids, with a putative mitochondrial targeting sequence and conserved sequence of the pyridoxal 5 0 -phosphate-binding domain. The recombinant Osl2 fusion protein over-expressed in Escherichia coli displays pyruvate-dependent g-aminobuty-ric acid (GABA) transaminase (EC 2.6.1.19) activity. Examination of the expression patterns of the Osl2 gene in rice reveals that Osl2-specific transcripts are induced in the senescing leaves. The temporal profile of Osl2 protein accumulation is correlated with that of pyruvate-dependent GABA transaminase activity in rice leaves, with the highest expression level at the S3 senescent stage. The potential role for GABA transaminase during rice leaf senescence is discussed.

Biologists and chemists of the world have been attracted towards marine natural products for the last five decades. Approximately 16,000 marine natural products have been isolated from marine organisms which have been reported in approximately 6,800 publications, proving marine microorganisms to be a invaluable source for the production of novel antibiotic, anti tumor, and anti inflammatory agents. The marine fungi particularly those associated with marine alga, sponge, invertebrates, and sediments appear to be a rich source for secondary metabolites, possessing Antibiotic, antiviral, antifungal and antiyeast activities. Besides, a few growth stimulant properties which may be useful in studies on wound healing, carcinogenic properties, and in the study of cancers are reported. Recent investigations on marine filamentous fungi looking for biologically active secondary metabolites indicate the tremendous potential of them as a source of new medicines. The present study reviews about some important bioactive metabolites reported from marine fungal strains which are anti bacterial, anti tumour and anti inflammatory in action. It highlights the chemistry and biological activity of the major bioactive alkaloids, polyketides, terpenoids, isoprenoid and non-isoprenoid compounds, quinones, isolated from marine fungi.

The currently accepted model of recombination-dependent replication (RDR) in plant mitochondrial DNA (mtDNA) does not clearly explain how RDR progresses and how highly complex mtDNA develops. This study aimed to investigate the correlation between RDR and mtDNA complexity during mitochondrial development in mung bean (Vigna radiata) seed, and the initiation and processing of RDR in plant mitochondria. Flow cytometry, pulsed-field gel electrophoresis, electron microscopy, real-time PCR and biochemical studies were used in this study. The highly dynamic changes in mtDNA complexity correspond to mtDNA RDR activity throughout mitochondrial development. With in vitro freeze-thaw treatment or prolonged in vivo cold incubation, the mtDNA rosette core disappeared and the rosette structure converted to a much longer linear DNA structure. D-loops, Holliday junctions and putative RDR forks often appeared near the rosette cores. We hypothesize that the rosette core may consist of condensed mtDNA and a replication starting sequence, and play an initial and central role in RDR. The satellite cores in the rosette structure may represent the re-initiation sites of mtDNA RDR in the same parental molecule, thereby forming highly complex and giant mitochondrial molecules, representing the RDR intermediates, in vivo.

No abstract

No abstract