Loss of a pyridoxal-phosphate phosphatase rescues Arabidopsis lacking an endoplasmic reticulum ATP carrier

Abstract

The endoplasmic reticulum (ER)-located ATP/ADP-antiporter (ER-ANT1) occurs specifically in vascular plants. Structurally different transporters mediate energy provision to the ER, but the cellular function of ER-ANT1 is still unknown. Arabidopsis (Arabidopsis thaliana) mutants lacking ER-ANT1 (er-ant1 plants) exhibit a photorespiratory phenotype accompanied by high glycine levels and stunted growth, pointing to an inhibition of glycine decarboxylase. To reveal whether it is possible to suppress this marked phenotype, we exploited the power of a forward genetic screen. Absence of a so far uncharacterized member of the HaloAcid Dehalogenase (HAD)-like hydrolase family strongly suppressed the dwarf phenotype of er-ant1 plants. Localization studies suggested that the corresponding protein locates to chloroplasts, and activity assays showed that the enzyme dephosphorylates, with high substrate affinity, the B6 vitamer pyridoxal 5'-phosphate (PLP). Additional physiological experiments identified imbalances in vitamin B6 homeostasis in er-ant1 mutants. Our data suggest that impaired chloroplast metabolism, but not decreased glycine decarboxylase (GDC) activity, causes the er-ant1 mutant dwarf phenotype. We present a hypothesis, setting transport of PLP by ER-ANT1 and chloroplastic PLP dephosphorylation in the cellular context. With the identification of this HAD-type PLP phosphatase, we also provide insight into B6 vitamer homeostasis.

PYRIDOX(AM)INE 5′-PHOSPHATE OXIDASE3 ofArabidopsis thalianamaintains carbon/nitrogen balance in distinct environmental conditions

“…Although, as nitrate assimilation is reduced under high CO 2 ( Bloom et al 2010 , 2020 ; Bloom 2015 ), this could account for the more drastic phenotype under this condition. This is in contrast to the recently described er-ant1 mutant which suffers a PLP deficiency that impacts photorespiration and is alleviated by growth under high CO 2 ( Altensell et al 2022 ). Thus, the pdx3 phenotype is a consequence of a different metabolic defect.…”

PDX3 is important for carbon/nitrogen balance in Arabidopsis associated with distinct environmental conditions

“…Although, as nitrate assimilation is reduced under high CO 2 (Bloom et al, 2010; Bloom, 2015; Bloom et al, 2020), this could account for the more drastic phenotype under this condition. This is in contrast to the recently described er-ant1 mutant which suffers a PLP deficiency that impacts photorespiration and is alleviated by growth under high CO 2 (Altensell et al, 2022). Thus, the pdx3 phenotype is a consequence of a different metabolic defect.…”

Bmo‐miR‐6498‐5p suppresses Bombyx mori nucleopolyhedrovirus infection by down‐regulating BmPLPP2 to modulate pyridoxal phosphate content in B. mori

“…In Escherichia coli （Enterobacteriaceae, Escherichia）a protein encoded by the gene YbhA was identified as a PLPP (Sugimoto et al, 2018). In Arabidopsis thaliana (Cruciferae, Arabidopsis), a PLPP protein (AtPLPP1) encoded by At2g33255 was annotated as a member of the HAD‐like superfamily and has 44% similarity to the YOR131C protein sequence, which was identified as a PLPP in Saccharomyces cerevisiae (Saccaromycetes, Saccharomycetaceae) (Altensell et al, 2022; Kuznetsova et al, 2015). In this study, we identified the BmPLPP2 as a PLPP which contains a HAD domain and a phosphatases domain.…”