Proteomic and functional analysis of proline dehydrogenase 1 link proline catabolism to mitochondrial electron transport in Arabidopsis thaliana

Abstract

Proline accumulates in many plant species in response to environmental stresses. Upon relief from stress, proline is rapidly oxidized in mitochondria by proline dehydrogenase (ProDH) and then by pyrroline-5-carboxylate dehydrogenase (P5CDH). Two ProDH genes have been identified in the genome of the model plant Arabidopsis thaliana To gain a better understanding of ProDH1 functions in mitochondria, proteomic analysis was performed. ProDH1 polypeptides were identified in Arabidopsis mitochondria by immunoblotting gels after 2D blue native (BN)-SDS/PAGE, probing them with an anti-ProDH antibody and analysing protein spots by MS. The 2D gels showed that ProDH1 forms part of a low-molecular-mass (70-140 kDa) complex in the mitochondrial membrane. To evaluate the contribution of each isoform to proline oxidation, mitochondria were isolated from wild-type (WT) and prodh1, prodh2, prodh1prodh2 and p5cdh mutants. ProDH activity was high for genotypes in which ProDH, most likely ProDH1, was strongly induced by proline. Respiratory measurements indicate that ProDH1 has a role in oxidizing excess proline and transferring electrons to the respiratory chain.

Metabolite Regulatory Interactions Control Plant Respiratory Metabolism via Target of Rapamycin (TOR) Kinase Activation

“…This mitochondrionlocalized pathway generates reducing power at both enzymatic steps that can then enter the mETC, fueling O 2 consumption. Respiration measurements on mitochondria isolated from 15-dold seedlings indicated that only PDH1 can mediate measurable Pro-dependent O 2 consumption (Cabassa-Hourton et al, 2016). Our results indicate that in mature leaves both PDH isoforms can contribute to Pro-dependent R N , consistent with their shared role in regulating Pro accumulation in senescing leaves (Launay et al, 2019).…”

“…We next observed that transcripts for both PDH isoforms in Arabidopsis, PDH1 and PDH2, increased during leaf disc incubation in Pro ( Figures 5B and 5C). PDH1 is expressed at a much higher level than PDH2 and is thought to represent the bulk of PDH activity (Funck et al, 2010;Cabassa-Hourton et al, 2016). Using confirmed T-DNA insertion lines (Funck et al, 2010), we assessed whether disruption of PDH gene expression would inhibit the ability of Pro to stimulate R N .…”

Overexpression of lily HsfA3s in Arabidopsis confers increased thermotolerance and salt sensitivity via alterations in proline catabolism

“…The positive regulatory role of proline accumulation under salt and osmotic stress is precise, but its physiological function under HS remains controversial ( Rizhsky et al , 2004 ; Miller et al , 2009 ; Verslues and Sharma, 2010 ; Cabassa-Hourton et al , 2016 ). Some reports have shown proline accumulating during HS; for example, when subjected to 41 °C, the proline content of the first leaf of barley ( Hordeum vulgare ) and radish ( Raphanus sativus ) showed a slight increase ( Chu et al , 1974 ).…”

Toward Unveiling the Mechanisms for Transcriptional Regulation of Proline Biosynthesis in the Plant Cell Response to Biotic and Abiotic Stress Conditions

“…Shared elements are expected to work as nodes , allowing the cross-talk. Since recent data suggest that high intracellular proline levels may induce in turn the catabolic pathway influencing mitochondrial respiration and reactive oxygen species generation (Ben Rejeb et al, 2014; Cabassa-Hourton et al, 2016), proline synthesis could represent one of these nodes. Further work is required to shed light on this possibility.…”