Report
of Taikichiro Mori Memorial Research Fund 2008
Research
Project: |
Cellular
dynamics |
Project
Name: |
Understanding the control and
dynamics of nitrogen response in yeast |
Name: |
Kalesh Sasidharan,
D2 |
Affiliation: |
Institute for Advanced
Biosciences, Graduate school of media and governance, Keio
University |
Introduction
My research is based on experimental
and computation biology. The Mori grant has given me a good opportunity to
improvise my research by equipping the lab with necessary equipments. I have
purchased a Mass Flow Controller,
which is an essential piece of equipment required for my research. Apart of
that, I have upgraded my computers and storage devices to store and process huge
amount of data files. My research theme, progress and final goals are given
below.
Research Project
Abstract
Yeast cells respond differently in
nitrogen rich and nitrogen deficient environment. When Saccharomyces
cerevisiae is grown on nitrogen sources that can readily be utilised, the
nitrogen catabolite repression (NCR) genes that code for the proteins involved
in the catabolism of poor nitrogen sources are not expressed, whereas during
growth on poor nitrogen sources the NCR genes will be activated [1]. This system
also acts in concert with general amino acid biosynthesis to form a highly
integrated sub-system in yeast that is widely conserved in eukaryotes.
Continuously grown cultures of yeast cells show robust oscillations in
respiration [2]. The population synchrony is the result of inter-cellular
metabolite communication, and is also correlated to the NAD(P)H and ATP oscillations (redox and energy metabolism).
Analysis of global gene expression level has shown specific patterns in
expression during the oscillation [3]. This further suggests that metabolism
related inter-cellular communication influences gene expression. Amino acid
biosyntheses are tightly regulated and the system is hyper-sensitive to nM concentrations of Rapamycin (derepressor of NCR genes)
during the oscillation. This signifies that both the function of general
nitrogen control (regulated by Gcn4p) and NCR regulation systems are linked.
However, the temporal regulation involved in the metabolic feedback of
metabolites on gene regulation in this system is remain
to be elucidated. Therefore, we are studying the functional interactions of
nitrogen regulatory control utilising continuously grown synchronous yeast
cultures. To clarify the network of transcriptional control of nitrogen, we are
constructing an expanded model from various experimental observations, such as
stress and perturbation conditions. This model will be experimentally validated
using precise culture conditions and perturbations coupled to state-of-the-art
experimental procedures. This validated model will further be used to get better
understanding of the emergence of coherent behaviour in combined metabolic and
transcriptional networks, i.e., self-organisation. This study will eventually
help us to obtain a better understanding of the role of metabolic, proteomic
controls in transcriptional mechanism.
References
1. T. G. Cooper.
Transmitting the signal of excess nitrogen in Saccharomyces
cerevisiae from the Tor proteins to the GATA factors: connecting the
dots. FEMS Microbiol Rev, 26(3):223-238, Aug
2002.
2. A. D. Satroutdinov, H. Kuriyama, and H.
Kobayashi. Oscillatory metabolism of Saccharomyces
cerevisiae in continuous culture. FEMS Microbiol Lett, 77(1-3):261-267,
Nov 1992.
3. D. B. Murray, M.
Beckmann, and H. Kitano. Regulation of yeast oscillatory
dynamics. PNAS,104(7):2241-2246, Feb
2007.