Biology subjects

Neupert, J.

Publications and source records attributed to Neupert, J..

2 recordsLinked to original sources

bioRxiv2023

The chloroplastic phosphate transporter CrPHT4-7 supports phosphate homeostasis and photosynthesis in Chlamydomonas

In eukaryotic cells, phosphorus is assimilated and utilized primarily as phosphate (Pi). Pi homeostasis is mediated by transporters that have not yet been adequately characterized in green algae. This study reports on CrPHT4-7 from Chlamydomonas reinhardtii, a member of the PHT4 transporter family, which exhibits remarkable similarity to AtPHT4;4 from Arabidopsis thaliana, a chloroplastic ascorbate transporter. Using fluorescent protein tagging we show that CrPHT4-7 resides in the chloroplast envelope membrane. Crpht4-7 mutants, generated by the CRISPR/Cas12a-mediated single-strand templated repair, show retarded growth especially in high light, enhanced sensitivity to phosphorus limitation, reduced ATP level, strong ascorbate accumulation and diminished non-photochemical quenching in high light. Conversely, CrPHT4-7 overexpressing lines exhibit enhanced biomass accumulation under high light conditions in comparison with the wild-type strain. Expressing CrPHT4-7 in a yeast strain lacking Pi transporters substantially recovered its slow growth phenotype demonstrating that it transports Pi. Even though CrPHT4-7 shows a high degree of similarity to AtPHT4;4, it does not display any significant ascorbate transport activity in yeast or intact algal cells. Thus, the results demonstrate that CrPHT4-7 functions as a chloroplastic Pi transporter essential for maintaining Pi homeostasis and photosynthesis in Chlamydomonas reinhardtii. One-sentence summaryWe demonstrate that the CrPHT4-7 transporter of Chlamydomonas reinhardtii is located in the chloroplast envelope membrane and contributes to maintaining phosphate homeostasis and photosynthesis.

plant biology↗

bioRxiv2019

Ascorbate deficiency does not limit non-photochemical quenching in Chlamydomonas reinhardtii

Ascorbate (vitamin C) plays essential roles in development, signaling, hormone biosynthesis, regulation of gene expression, stress resistance and photoprotection. In vascular plants, violaxanthin de-epoxidase (VDE) requires ascorbate (Asc) as reductant, thereby it is required for the energy-dependent component of non-photochemical quenching (NPQ). In order to assess the role of Asc in NPQ in green algae, which are known to contain low amounts of Asc, we searched for an insertional Chlamydomonas reinhardtii mutant affected in the VTC2 gene, essential for Asc biosynthesis. The Crvtc2-1 knockout mutant was viable and, depending on the growth conditions, it contained 10 to 20% Asc relative to its wild type. When Chlamydomonas was grown photomixotrophically at moderate light, the zeaxanthin-dependent component of NPQ emerged upon strong red illumination both in the Crvtc2-1 mutant and in its wild type. Deepoxidation was unaffected by Asc deficiency, demonstrating that the Chlorophycean VDE found in Chlamydomonas does not require Asc as a reductant. The rapidly induced, energy-dependent NPQ component, characteristic of photoautotrophic Chlamydomonas cultures grown at high light, was not limited by Asc deficiency either. On the other hand, a reactive oxygen species-induced photoinhibitory NPQ component was greatly enhanced upon Asc deficiency, both under photomixotrophic and photoautotrophic conditions. These results demonstrate that Asc has distinct roles in NPQ formation in Chlamydomonas than in vascular plants.\n\nOne-sentence summaryIn Chlamydomonas -in contrast to seed plants-, ascorbate is not required for violaxanthin deepoxidation and energy-dependent non-photochemical quenching but it mitigates photoinhibitory quenching.

plant biology↗