Research overview

Project 1: Mechanism of caffeine action in cellular slime molds:The nucleoside adenosine induces large aggregate formation favoring stalk cell differentiation in different cellular slime molds. On the other hand, the adenosine antagonist, caffeine, reduces the group size and induces multiple tip formation in Dictyostelium and distantly related slime molds. Thus the target(s) of caffeine could potentially be involved in lateral inhibition, a problem of great interest in embryonic pattern formation. Using candidate gene approaches and proteomics tools, we are examining the targets of caffeine action in slime molds. Besides, we are examining the transcriptional changes brought about by adenosine and caffeine that are involved in lateral inhibition. Collaborators: Ludwig Eichinger, University of Cologne, Germany and Thierry Soldati, University of Geneva, Switzerland.

Project 2: Do slime molds make use of bacterial volatiles to track its prey? Cellular slime mold amoebae feed on bacteria and multiply. These predatory amoebae track its prey by the presence of folic acid secreted by the bacteria. However, if the food is present at considerable distance where folic acid cannot diffuse and reach the amoebae, then volatiles from bacteria may be sensed by the amoebae thereby finding the bacteria. We are trying to ascertain if this is true using a combination of molecular genetic tools and chemotaxis assays.

Project 3: Characterization of thyroxine 5' deiodinase (dio3) and putative protein kinase C in Disctyostelium: The hormone thyroxine is present in a number of higher eukaryotes but surprisingly, a gene involved in thyroxine metabolism, thyroxine 5'deiodinase (dio3) is also present in Dictyostelium, a lower eukaryote. To know the function of this gene in development, we generated a dio3 knockout and found several defects in signaling and development. A detailed description of the phenotype can be found in the paper Singh et al., (2015) Developmental Biology.

Independently, we generated a knockout of a putative protein kinase-C in Dictyostelium by homologous recombination and a prominent phenotype is the breaking of late aggregates into small signaling centers each forming a fruiting body of its own. The detailed characterization of the phenotype is underway. 

Project 4: Parental age effects on the somatic mutation rates in flowering plants: It is well known that the reproductive age of the parents matters in the health of the progeny. However, it is not known if parental age also affects somatic mutations which are difficult to detect. By taking advantage of the plant model system Arabidopsis thaliana, where mutation detector lines allow for an easy quantitation of somatic mutations, we found that the parental reproductive age has a strong effect on the spontaneous mutation rates in the progeny. We are examining if meiotic recombination rates also vary in plants derived from parents of different age groups. For details see: Singh et al (2015) Plant Physiology. Collaborator: Ueli Grossniklaus, University of Zurich. Switzerland.

Project 5: Somatic mutation induced upon hybridization (completed) We are examining if hybridization among close and wide relatives of Arabidopsis induces a change in the spontaneous mutation rates among the F1 hybrids. With a set of transgenic lines carrying mutated or truncated versions of the GUS reporter gene reversion assays are carried out to know if F1 hybrids show altered mutation rates than the parental lines. We assay for point and frame shift mutations, homologous recombination and transpositions. Specifically, this project will address the following questions: (1) Does hybridization favour or suppress a particular kind of mutation over others? (2) Does the genetic distance between different parental lines (here ecotypes or accessions) have any consequence on the mutation frequency? (3) Does the direction of the cross influence the mutation load (parental effect)?