Dataset Information

Transcriptional Regulation of the Glucose-6-Phosphate/Phosphate Translocator 2 Is Related to Carbon Exchange Across the Chloroplast Envelope.

ABSTRACT: The exchange of reduced carbon across the inner chloroplast envelope has a large impact on photosynthesis and growth. Under steady-state conditions it is thought that glucose 6-phosphate (G6P) does not cross the chloroplast membrane. However, growth at high CO2, or disruption of starch metabolism can result in the GPT2 gene for a G6P/Pi translocator to be expressed presumably allowing G6P exchange across the chloroplast envelope. We found that after an increase in light, the transcript for GPT2 transiently increases several 100-fold within 2 h in both the Col-0 and WS ecotypes of Arabidopsis thaliana. The increase in transcript for GPT2 is preceded by an increase in transcript for many transcription factors including Redox Responsive Transcription Factor 1 (RRTF1). The increase in GPT2 transcript after exposure to high light is suppressed in a mutant lacking the RRTF1 transcription factor. The GPT2 response was also suppressed in a mutant with a T-DNA insert in the gene for the triose-phosphate/Pi translocator (TPT). However, plants lacking TPT still had a robust rise in RRTF1 transcript in response to high light. From this, we conclude that both RRTF1 (and possibly other transcription factors) and high amounts of cytosolic triose phosphate are required for induction of the expression of GPT2. We hypothesize that transient GPT2 expression and subsequent translation is adaptive, allowing G6P to move into the chloroplast from the cytosol. The imported G6P can be used for starch synthesis or may flow directly into the Calvin-Benson cycle via an alternative pathway (the G6P shunt), which could be important for regulating and stabilizing photosynthetic electron transport and carbon metabolism.

SUBMITTER: Weise SE

PROVIDER: S-EPMC6609314 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Transcriptional Regulation of the Glucose-6-Phosphate/Phosphate Translocator 2 Is Related to Carbon Exchange Across the Chloroplast Envelope.

Weise Sean E SE Liu Tiffany T Childs Kevin L KL Preiser Alyssa L AL Katulski Hailey M HM Perrin-Porzondek Christopher C Sharkey Thomas D TD

Frontiers in plant science 20190627

The exchange of reduced carbon across the inner chloroplast envelope has a large impact on photosynthesis and growth. Under steady-state conditions it is thought that glucose 6-phosphate (G6P) does not cross the chloroplast membrane. However, growth at high CO2, or disruption of starch metabolism can result in the GPT2 gene for a G6P/Pi translocator to be expressed presumably allowing G6P exchange across the chloroplast envelope. We found that after an increase in li ...[more]

PMID: 31316533

Similar Datasets

Project description:The xylulose 5-phosphate/phosphate translocator (PTs) (XPT) represents a link between the plastidial and extraplastidial branches of the oxidative pentose phosphate pathway. Its role is to retrieve pentose phosphates from the extraplastidial space and to make them available to the plastids. However, the XPT transports also triose phosphates and to a lesser extent phosphoenolpyruvate (PEP). Thus, it might support both the triose phosphate/PT (TPT) in the export of photoassimilates from illuminated chloroplasts and the PEP/PT (PPT) in the import of PEP into green or non-green plastids. In mutants defective in the day- and night-path of photoassimilate export from the chloroplasts (i.e., knockout of the TPT [tpt-2] in a starch-free background [adg1-1])the XPT provides a bypass for triose phosphate export and thereby guarantees survival of the adg1-1/tpt-2 double mutant. Here we show that the additional knockout of the XPT in adg1-1/tpt-2/xpt-1 triple mutants results in lethality when the plants were grown in soil. Thus the XPT can functionally support the TPT. The PEP transport capacity of the XPT has been revisited here with a protein heterologously expressed in yeast. PEP transport rates in the proteoliposome system were increased with decreasing pH-values below 7.0. Moreover, PEP transport determined in leaf extracts from wild-type plants showed a similar pH-response, suggesting that in both cases PEP2- is the transported charge-species. Hence, PEP import into illuminated chloroplasts might be unidirectional because of the alkaline pH of the stroma. Here the consequence of a block in PEP transport across the envelope was analyzed in triple mutants defective in both PPTs and the XPT. PPT1 is knocked out in the cue1 mutant. For PPT2 two new mutant alleles were isolated and established as homozygous lines. In contrast to the strong phenotype of cue1, both ppt2 alleles showed only slight growth retardation. As plastidial PEP is required e.g., for the shikimate pathway of aromatic amino acid synthesis, a block in PEP import should result in a lethal phenotype. However, the cue1-6/ppt2-1/ppt2-1 triple mutant was viable and even exhibited residual PEP transport capacity. Hence, alternative ways of PEP transport must exist and are discussed.

Dataset Information

Transcriptional Regulation of the Glucose-6-Phosphate/Phosphate Translocator 2 Is Related to Carbon Exchange Across the Chloroplast Envelope.

Publications

Transcriptional Regulation of the Glucose-6-Phosphate/Phosphate Translocator 2 Is Related to Carbon Exchange Across the Chloroplast Envelope.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets