Plant DNA Recombinases: A Long Way to Go

DNA homologous recombination is fundamental process by which two homologous DNA molecules exchange the genetic information for the generation of genetic diversity and maintain the genomic integrity. DNA recombinases, a special group of proteins bind to single stranded DNA (ssDNA) nonspecifically and search the double stranded DNA (dsDNA) molecule for a stretch of DNA that is homologous with the bound ssDNA. Recombinase A (RecA) has been well characterized at genetic, biochemical, as well as structural level from prokaryotes. Two homologues of RecA called Rad51 and Dmc1 have been detected in yeast and higher eukaryotes and are known to mediate the homologous recombination in eukaryotes. The biochemistry and mechanism of action of recombinase is important in understanding the process of homologous recombination. Even though considerable progress has been made in yeast and human recombinases, understanding of the plant recombination and recombinases is at nascent stage. Since crop plants are subjected to different breeding techniques, it is important to know the homologous recombination process. This paper focuses on the properties of eukaryotes recombinases and recent developments in the field of plant recombinases Dmc1 and Rad51

Modularity: A New Perspective in Biology

133-139Several decades of research in biochemistry and molecular biology have been devoted for studies on isolated enzymes and proteins. Recent high throughput technologies in genomics and proteomics have resulted in avalanche of information about several genes, proteins and enzymes in variety of living systems. Though these efforts have greatly contributed to the detailed understanding of a large number of individual genes and proteins, this explosion of information has simultaneously brought out the limitations of reductionism in understanding complex biological processes. The genes or gene products do not function in isolation in vivo. A delicate and dynamic molecular architecture is required for precision of the chemical reactions associated with “life”. In future, a paradigm shift is, therefore, envisaged, in biology leading to exploration of molecular organizations in physical and genomic context, a subtle transition from conventional molecular biology to modular biology. A module can be defined as an organization of macromolecules performing a synchronous function in a given metabolic pathway. In modular biology, the biological processes of interest are explored as complex systems of functionally interacting macromolecules. The present article describes the perceptions of the concept of modularity, in terms of associations among genes and proteins, presenting a link between reductionist approach and system biology

Employing a photosynthetic antenna complex to interfacial electron transfer on ZnO quantum dot

Photosynthetic antenna complexes exhibit unidirectional energy-transport phenomena, which make them potential photosensitizers in interfacial electron-transfer processes. In the present study, we show the antenna function of phycocyanin-allophycocyanin (PC−APC) complex using transient emission and absorption spectroscopy. Interfacial electron-transfer dynamics in the PC−APC complex sensitized ZnO semiconductor quantum dot material is compared in native and denatured conditions. The downhill sequential energy transfer from a peripheral phycocyanin disk to a core allophycocyanin disk opens a new electron injection pathway from the allophycocyanin disk in addition to primary electron injection from directly photoexcited phycocyanin disk. Further, the large association of phycocayanobilin chromophores in PC−APC conjugates stabilizes the positive charge within the sensitizer, which leads to slower charge recombination in comparison to that in denatured condition. This study displays the antenna function of energy-efficient biomolecules in favor of better charge separation across the semiconductor interface

Homologous recombination properties of OsRad51, a recombinase from rice

cDNA corresponding to OsRad51 protein was isolated from cDNA library of rice flowers (Oryzasativa, Indica cultivar group) and cloned in to pET28a expression vector. The protein was over expressed in E. coli BL21 (DE3) and purified. Purified OsRad51 could bind single and double stranded DNA, however it showed higher affinity for single stranded DNA. Transmission Electron Microscopy (TEM) studies of OsRad51–DNA complexes showed that this protein formed ring like structures and bound DNA forming filaments. OsRad51 protein promoted renaturation of complementary single strands in to duplex DNA molecules and also showed ATPase activity, which was stimulated by single strand DNA. Fluorescence resonance energy transfer (FRET) assays revealed that OsRad51 promoted homology dependent renaturation as well as strand exchange reactions. Renaturation activity was ATP dependent; however strand exchange activity was ATP independent. This is the first report on in vitro characterization of Rad51 protein from crop plants

Employing a Photosynthetic Antenna Complex to Interfacial Electron Transfer on ZnO Quantum Dot

Photosynthetic antenna complexes exhibit unidirectional energy-transport phenomena, which make them potential photosensitizers in interfacial electron-transfer processes. In the present study, we show the antenna function of phycocyanin-allophycocyanin (PC−APC) complex using transient emission and absorption spectroscopy. Interfacial electron-transfer dynamics in the PC−APC complex sensitized ZnO semiconductor quantum dot material is compared in native and denatured conditions. The downhill sequential energy transfer from a peripheral phycocyanin disk to a core allophycocyanin disk opens a new electron injection pathway from the allophycocyanin disk in addition to primary electron injection from directly photoexcited phycocyanin disk. Further, the large association of phycocayanobilin chromophores in PC−APC conjugates stabilizes the positive charge within the sensitizer, which leads to slower charge recombination in comparison to that in denatured condition. This study displays the antenna function of energy-efficient biomolecules in favor of better charge separation across the semiconductor interface