Elucidation of functional and regulatory aspects of sulfate transport in Chlamydomonas reinhardtii
Abstract/Contents
- Abstract
- Chlamydomonas reinhardtii (Chlamydomonas) exhibits a suite of responses to sulfur (S) deprivation, including an elevation of sulfate uptake, synthesis of extracellular arylsulfatase, down-regulation of photosynthesis and cessation of growth and cell division. One of the earliest responses to S starvation is an increase in the sulfate transport rate. Aspects of sulfate transport during S-replete and S-depleted conditions were previously studied, although the sulfate transporters had not been functionally identified. In this study, both forward and reverse genetic approaches were employed to identify sulfate transporters in Chlamydomonas. SULTR2, SLT1, and SLT2 transcripts and polypeptides increased markedly in S-starved wild-type cells, suggesting that these genes encode high-affinity sulfate transporters that function when the cells experience S limitation. Mutant strains defective for acclimation to S starvation, sac1 and snrk2.1, exhibited much less of an increase in the level of SULTR2, SLT1, and SLT2 transcripts and their encoded proteins during S deprivation compared to wild-type cells. Consequently, these two strains were unable to induce sulfate uptake to the same extent as in the wild-type strain. The SULTR2, SLT1 and SLT2 polypeptides were localized to the plasma membrane and their rates of turnover were significantly impacted by S availability; the turnover for SLT1 and SLT2 (but not for SULTR2) was demonstrated to be dependent on proteasome function. Mutants identified for each of the S-deprivation-responsive transporters were used to establish their critical role in the transport of sulfate into S-starved cells. I have also discovered a sequential, temporal regulation of the S-starvation responsive genes. The primary responses (e.g. the induction of high-affinity SO[not]42- transporters) are not dependent on protein synthesis occurring on 80S ribosomes. In contrast, the secondary responses (the induction of ARS, ECP76 and ECP88) require de novo protein synthesis. ARS73a, a putative transcriptional activator, is directly or indirectly involved in the regulation of the expression of the second tier genes, most of which encode proteins associated with the scavenging of extracellular S or the redistribution of internal S. Genetic analysis has shown that ARS73a and SAC3 kinase act in the same pathway; ARS73a is epistatic to SAC3. These new discoveries are incorporated into a model that describes S-deprivation elicited regulation in Chlamydomonas.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2010 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Pootakham, Wirulda |
|---|---|
| Associated with | Stanford University, Department of Biological Sciences |
| Primary advisor | Cyert, Martha S, 1958- |
| Primary advisor | Grossman, Arthur (Arthur R.) |
| Thesis advisor | Cyert, Martha S, 1958- |
| Thesis advisor | Grossman, Arthur (Arthur R.) |
| Thesis advisor | Mudgett, Mary Beth, 1967- |
| Thesis advisor | Wang, Zhi-Yong, Dr |
| Advisor | Mudgett, Mary Beth, 1967- |
| Advisor | Wang, Zhi-Yong, Dr |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Wirulda Pootakham. |
|---|---|
| Note | Submitted to the Department of Biology. |
| Thesis | Ph.D. Stanford University 2010 |
| Location | electronic resource |
Access conditions
- Copyright
- © 2010 by Wirulda Pootakham
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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