<p>Exposure to ultraviolet
radiation (UVR) has been shown to cause cellular damage in cyanobacteria. In
response to UVR exposure, some cyanobacteria produce scytonemin, an
indole-alkaloid sunscreen capable of absorbing long-wavelength UVA radiation.
Previous genomic and transcriptomic analyses have determined that the
production of scytonemin is controlled by a two-component regulatory system
(TCRS), encoded by Npun_F1277 and Npun_F1278 in the cyanobacterium <i>Nostoc punctiforme </i>ATCC 29133. This TCRS
is thought to not only regulate scytonemin biosynthesis, but also other
responses to light and UVR stimuli. To better understand the functionality of
the sensor kinase (SK) Npun_F1277 and to determine if it could activate
alternative UVR protection pathways, the SK was expressed in <i>Escherichia coli.</i> The first objective of
this study was to observe and quantify the level of fitness conferred to <i>E. coli</i> expressing Npun_F1277 from <i>N. punctiforme </i>(strain SKE) when exposed to white light, UVA, and UVB stress. Results
from these experiments do not indicate that expression of the <i>N. punctiforme</i>
SK conferred an advantage to <i>E. coli</i> under white light, UVA, or UVB
stress based on growth alone. Therefore, the second objective was to study the
expression of regulatory genes, such as response regulators, in <i>E. coli</i>
that are homologs to those associated with the SK Npun_F1277 in <i>N. punctiforme
</i>using quantitative-PCR. Expression of the selected genes was measured
following exposure to white light and UVA after 30 and 60 minutes as well as
UVB after 15 and 30 minutes. Comparison of SKE to empty-vector (EV) control
cells exposed to the same stress showed that there were significant changes in
the expression of important regulatory genes (e.g. <i>recA, spoT, relA</i>) in
the SKE strain. Moreover, when comparing SKE cells exposed to the same
conditions above to unstressed SKE cells, a similar result was seen for SKE
cells exposed to UVA and UVB as was found in the studies comparing SKE to EV
cells. These results suggest that the SK Npun_F1277 may play a role in multiple
defense mechanisms of <i>N. punctiforme</i>
in addition to initiation of the scytonemin biosynthesis pathway. </p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/12202271 |
| Date | 28 April 2020 |
| Creators | Adreian Alexander Paul (8770571) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/Analysis_of_a_Cyanobacterial_UV-Sensitive_Sensor_Kinase_Expressed_in_i_Escherichia_coli_i_/12202271 |
Page generated in 0.0025 seconds