Pyrroline-5-carboxylate metabolism protein complex detected in Arabidopsis thaliana leaf mitochondria

• Published in: Journal of experimental botany 2024-02, Vol.75 (3), p.917-934
• Main Authors: Zheng, Yao, Cabassa-Hourton, Cécile, Eubel, Holger, Chevreux, Guillaume, Lignieres, Laurent, Crilat, Emilie, Braun, Hans-Peter, Lebreton, Sandrine, Savouré, Arnould
• Format: Article
• Language: English
• Subjects: Arabidopsis - metabolism; Biochemistry, Molecular Biology; Botanics; Glutamates - metabolism; Life Sciences; Mitochondria - metabolism; Ornithine - metabolism; Proline - metabolism; Proline Oxidase - chemistry; Proline Oxidase - metabolism; Pyrroles; Vegetal Biology
• ISSN: 0022-0957; 1460-2431; 1460-2431
• DOI: 10.1093/jxb/erad406

Abstract Proline dehydrogenase (ProDH) and pyrroline-5-carboxylate (P5C) dehydrogenase (P5CDH) catalyse the oxidation of proline into glutamate via the intermediates P5C and glutamate-semialdehyde (GSA), which spontaneously interconvert. P5C and GSA are also intermediates in the production of glutamate from ornithine and α-ketoglutarate catalysed by ornithine δ-aminotransferase (OAT). ProDH and P5CDH form a fused bifunctional PutA enzyme in Gram-negative bacteria and are associated in a bifunctional substrate-channelling complex in Thermus thermophilus; however, the physical proximity of ProDH and P5CDH in eukaryotes has not been described. Here, we report evidence of physical proximity and interactions between Arabidopsis ProDH, P5CDH, and OAT in the mitochondria of plants during dark-induced leaf senescence when all three enzymes are expressed. Pairwise interactions and localization of the three enzymes were investigated using bimolecular fluorescence complementation with confocal microscopy in tobacco and sub-mitochondrial fractionation in Arabidopsis. Evidence for a complex composed of ProDH, P5CDH, and OAT was revealed by co-migration of the proteins in native conditions upon gel electrophoresis. Co-immunoprecipitation coupled with mass spectrometry analysis confirmed the presence of the P5C metabolism complex in Arabidopsis. Pull-down assays further demonstrated a direct interaction between ProDH1 and P5CDH. P5C metabolism complexes might channel P5C among the constituent enzymes and directly provide electrons to the respiratory electron chain via ProDH. Dark-induced leaf senescence in Arabidopsis results in the presence of a mitochondrial complex consisting of at least proline dehydrogenase, pyrroline-5-carboxylate dehydrogenase, and ornithine δ-aminotransferase.