Title |
Functional analysis of Mpk1-mediated cell wall integrity signaling pathway in the thermotolerant methylotrophic yeast Hansenula polymorpha |
Author |
Hyunah Kim1, Eun Jung Thak1, Ji Yoon Yeon1, Min Jeong Sohn1, Jin Ho Choo1, Jeong-Yoon Kim2*, and Hyun Ah Kang1* |
Address |
1Department of Life Science, Chung-Ang University, Seoul 06974, Republic of Korea, 2Department of Microbiology and Molecular Biology, Chungnam National University, Daejeon 34134, Republic of Korea |
Bibliography |
Journal of Microbiology, 56(1),72–82, 2018,
|
DOI |
10.1007/s12275-018-7508-6
|
Key Words |
Hansenula polymorpha, cell wall integrity, Mpk1,
Hog1, caffeine |
Abstract |
Understanding the characteristics and regulation mechanisms
of cell wall integrity (CWI) in yeast is important not
only for basic research but also in biotechnological applications.
We found significantly different CWIs in two representative
strains of the thermotolerant methylotrophic yeast
Hansenula polymorpha. Compared to the A16 strain (classified
as Ogataea polymorpha), the DL1-L strain (classified as
Ogataea parapolymorpha) has a thinner cell wall that was
found to be more fragile following long-term cultivation and
more sensitive to zymolyase. To gain a deeper insight into this
difference, we compared the characteristics of the Mpk1pmediated
CWI signaling pathway in the two strains. While
a DL1-L mutant deficient in Mpk1p (mpk1Δ) showed severe
growth retardation at both normal and high growth temperatures
and in the presence of cell-wall disrupting agents, the
A16 mpk1Δ mutant displayed only a mild defect in cell growth.
Sorbitol effect on rescuing growth retardation was different
in the two mpk1Δ strains, which could partly be ascribed to
subtle differences in the activation of HOG pathway. Among
the cell wall disruptors evaluated, only caffeine clearly increased
phosphorylation of Mpk1p in DL1-L, but not in A16.
A transcriptome analysis of the DL1-L strain revealed that
caffeine significantly increased the expression of a subset of
cell-wall related genes in an Mpk1p-dependent manner, but
not the expected Rlm1-target genes. Taken together, our data
support an essential role for Mpk1p in maintaining CWI in
H. polymorpha, although the requirement for Mpk1p and
its regulation under diverse stress conditions varies depending
on the strain background. |