The role of three-tandem Pho Boxes in the control of the C-P lyase operon in a thermophilic cyanobacterium

Cyanobacteria have an inherited advantage in phosphonate phytoremediation. However, studies on phosphonate metabolism in cyanobacteria are rare and mostly focus on physiology and ecology. Here, C-P lyase gene cluster regulation in an undomesticated thermophilic Synechococcus OS-B′ was examined in Synechocystis sp. PCC6803, a unicellular cyanobacterial model. Phylogenetic and cluster synteny analysis of C-P lyase genes revealed a closer relationship between Syn OS-B′ and Thermus thermophilus, than with other cyanobacteria. Pho boxes were identified in the 5′-end-flanking region of the C-P lyase gene cluster, through which the downstream gene expression was regulated in a phosphate concentration-dependent manner. Unexpectedly, the phosphate concentration that thoroughly inhibited Pho boxes was almost two orders of magnitude higher than that of any natural or anthropogenic wastewater reported so far. The Pho boxes mediated regulation was achieved through the Pho regulon two-component system, and the absence of either SphS or SphR ablated the cell's ability to sense ambient phosphate changes. The three tandems of Pho boxes maintained inequivalent roles, of which the third tandem was not essential; however, it played a role in adjusting Pho boxes response in both positive and negative manner under phosphorus limitation.     

Motility Enhancement through Surface Modification Is Sufficient for Cyanobacterial Community Organization during Phototaxis

The emergent behaviors of communities of genotypically identical cells cannot be easily predicted from the behaviors of individual cells. In many cases, it is thought that direct cell-cell communication plays a critical role in the transition from individual to community behaviors. In the unicellular photosynthetic cyanobacterium Synechocystis sp. PCC 6803, individual cells exhibit light-directed motility (“phototaxis”) over surfaces, resulting in the emergence of dynamic spatial organization of multicellular communities. To probe this striking community behavior, we carried out time-lapse video microscopy coupled with quantitative analysis of single-cell dynamics under varying light conditions. These analyses suggest that cells secrete an extracellular substance that modifies the physical properties of the substrate, leading to enhanced motility and the ability for groups of cells to passively guide one another. We developed a biophysical model that demonstrates that this form of indirect, surface-based communication is sufficient to create distinct motile groups whose shape, velocity, and dynamics qualitatively match our experimental observations, even in the absence of direct cellular interactions or changes in single-cell behavior. Our computational analysis of the predicted community behavior, across a matrix of cellular concentrations and light biases, demonstrates that spatial patterning follows robust scaling laws and provides a useful resource for the generation of testable hypotheses regarding phototactic behavior. In addition, we predict that degradation of the surface modification may account for the secondary patterns occasionally observed after the initial formation of a community structure. Taken together, our modeling and experiments provide a framework to show that the emergent spatial organization of phototactic communities requires modification of the substrate, and this form of surface-based communication could provide insight into the behavior of a wide array of biological communities.     

Physiological characterisation of Colletotrichum gloeosporioides,the incitant of anthracnose disease of noni in India

Ten isolates of Colletotrichum gloeosporioides were collected from different noni growing areas of Tamil Nadu, Karnataka and Kerala in India and their pathogenicity was proved under glass house conditions. Effect of different pH levels, temperature, light intensity and media were tested against the growth of C. gloeosporioides under in vitro. The results indicated that the growth of C. gloeosporioides was maximum in pH range of 6.50–7.00 and temperature range of 25–30°C. Exposure of the fungus to alternate cycles of 12 h light and 12 h darkness resulted in the maximum mycelial growth of C. gloeosporioides compared to the 24 h exposure to continuous light and 24 h exposure to continuous dark. Among the different media tested, host leaf extract medium supported significantly the maximum growth of all the 10 isolates of C. gloeosporioides followed by potato dextrose agar. Further, the strains were found to vary morphologically between the isolates under the study.     

Isolation of apolipoprotein-free lipoprotein lipase from human post-heparin plasma

Lipoprotein lipase from human post-heparin plasma was purified at least 10,000-fold using the Fielding procedure. When the purified lipoprotein lipase was subjected to polyacrylamide electrophoresis, a single band with lipolytic activity and four additional bands were observed. These four bands are identical in their electrophoretic and immunochemical properties to the polypeptides of apolipoprotein C. Evidence is presented which suggests that one or more of these polypeptides may serve as a partial activator of this enzyme.     

Aberrant vegetative and reproductive development by overexpression and lethality by silencing of OsHAP3E in rice

We generated transgenic rice plants overexpressing OsHAP3E which encodes a subunit of a CCAAT-motif binding HAP complex. The OsHAP3E-overexpressing plants showed various abnormal morphologies both in their vegetative and reproductive phases. The OsHAP3E-overexpressing plants were dwarf with erected leaves and similar to brassinosteroid mutants in the vegetative phase. In the reproductive phase, dense panicle was developed, and occasionally successive generation of lateral rachises and formation of double flowers were observed. These phenotypes indicate association of OsHAP3E with determination of floral meristem identity. On the other hand, repression of OsHAP3E by RNAi or by overexpressing chimeric repressor fusion constructs brought about lethality to transformed cells, and almost no transformant was obtained. This suggests that the OsHAP3E function is essential for rice cells. Altogether, our loss-of-function and gain-of-function analyses suggest that OsHAP3E plays important pleiotropic roles in vegetative and reproductive development or basic cellular processes in rice.