An Oxalyl-CoA Synthetase Is Involved in Oxalate Degradation and Aluminum Tolerance

Abstract

Acyl Activating Enzyme3 (AAE3) was identified to be involved in the catabolism of oxalate, which is critical for seed development and defense against fungal pathogens. However, the role of AAE3 protein in abiotic stress responses is unknown. Here, we investigated the role of rice bean (Vigna umbellata) VuAAE3 in Al tolerance. Recombinant VuAAE3 protein has specific activity against oxalate, with K m = 121 6 8.2 mM and V max of 7.7 6 0.88 mmol min 21 mg 21 protein, indicating it functions as an oxalyl-CoA synthetase. VuAAE3-GFP localization suggested that this enzyme is a soluble protein with no specific subcellular localization. Quantitative reverse transcription-PCR and VuAAE3 promoter-GUS reporter analysis showed that the expression induction of VuAAE3 is mainly confined to rice bean root tips. Accumulation of oxalate was induced rapidly by Al stress in rice bean root tips, and exogenous application of oxalate resulted in the inhibition of root elongation and VuAAE3 expression induction, suggesting that oxalate accumulation is involved in Al-induced root growth inhibition. Furthermore, overexpression of VuAAE3 in tobacco (Nicotiana tabacum) resulted in the increase of Al tolerance, which was associated with the decrease of oxalate accumulation. In addition, NtMATE and NtALS3 expression showed no difference between transgenic lines and wildtype plants. Taken together, our results suggest that VuAAE3-dependent turnover of oxalate plays a critical role in Al tolerance mechanisms.

The oxalyl‐CoA synthetase‐regulated oxalate and its distinct effects on resistance to bacterial blight and aluminium toxicity in rice

“…; Lou et al . ). In certain other oxalate‐degrading microbes, oxalyl‐CoA could be reduced back to glyoxylate, where a glyoxylate dehydrogenase is responsible for the catalysis.…”

Regulating cytoplasmic oxalate homeostasis by Acyl activating enzyme3 is critical for plant Al tolerance

“…14 To date, AAE3 proteins from rice bean, Medicago truncatula, and Arabidopsis (Arabidopsis thaliana) have been characterized as oxalyl-CoA synthetases. 13,15,16 Here, amino acid sequence alignment revealed that AAE3 proteins from common buckwheat and amaranth display high identity with known AAE3 proteins, all having a conserved AMP binding domain and acetylCoA synthetase domain (Fig. 2).…”

“…However, we previously demonstrated that oxalate accumulation is harmful for root growth in response to Al stress in rice bean (Vigna umbellata). 13 We further identified a gene VuAAE3 (Vigna umbellata Acyl Activating Enzyme3) that converts oxalate to oxalyl-CoA, thereby preventing oxalate toxicity induced by Al stress. 13 Although in silico analysis revealed that AAE3 proteins seem to be conserved among plant species, more evidence is required to support the viewpoint that AAE3 proteins-dependent Al resistance mechanism is conserved among plant species.…”

“…13 We further identified a gene VuAAE3 (Vigna umbellata Acyl Activating Enzyme3) that converts oxalate to oxalyl-CoA, thereby preventing oxalate toxicity induced by Al stress. 13 Although in silico analysis revealed that AAE3 proteins seem to be conserved among plant species, more evidence is required to support the viewpoint that AAE3 proteins-dependent Al resistance mechanism is conserved among plant species. In the present study, we provided more compelling evidence that regulating of cytoplasmic oxalate homeostasis by AAE3 proteins provides additional layer of Al resistance mechanisms in plants.…”

“…Although the biochemical and molecular biological characterization of FeAAE3 and AhAAE3 proteins has to be investigated, it is reasonable to suggest that they also function as oxalyl-CoA synthetases. Given that AAE3 protein is characterized by having activities specific to oxalate, 13,15,16 the upregulation of AAE3 genes suggests that oxalate accumulates under Al stress.…”