Aldehyde Dehydrogenases Function in the Homeostasis of Pyridine Nucleotides in Arabidopsis thaliana

Tagnon D Missihoun,Dorothea Bartels,Simeon O Kotchoni

doi:10.1038/s41598-018-21202-6

Abstract

Aldehyde dehydrogenase enzymes (ALDHs) catalyze the oxidation of aliphatic and aromatic aldehydes to their corresponding carboxylic acids using NAD+ or NADP+ as cofactors and generating NADH or NADPH. Previous studies mainly focused on the ALDH role in detoxifying toxic aldehydes but their effect on the cellular NAD(P)H contents has so far been overlooked. Here, we investigated whether the ALDHs influence the cellular redox homeostasis. We used a double T-DNA insertion mutant that is defective in representative members of Arabidopsis thaliana ALDH families 3 (ALDH3I1) and 7 (ALDH7B4), and we examined the pyridine nucleotide pools, glutathione content, and the photosynthetic capacity of the aldh mutants in comparison with the wild type. The loss of function of ALDH3I1 and ALDH7B4 led to a decrease of NAD(P)H, NAD(P)H/NAD(P) ratio, and an alteration of the glutathione pools. The aldh double mutant had higher glucose-6-phosphate dehydrogenase activity than the wild type, indicating a high demand for reduced pyridine nucleotides. Moreover, the mutant had a reduced quantum yield of photosystem II and photosynthetic capacity at relatively high light intensities compared to the wild type. Altogether, our data revealed a role of ALDHs as major contributors to the homeostasis of pyridine nucleotides in plants.

Highlights

To investigate whether the Aldehyde dehydrogenase enzymes (ALDHs) influence the cellular redox, we examined their contribution to the pyridine nucleotide NAD(P) and NAD(P)H pools by using a double T-DNA insertion mutant (KO6/62) of A. thaliana that is defective in the ALDH7B4 and ALDH3I1 genes
The NAD(P)H/NAD(P) ratio significantly decreased by 32% in the double mutant KO6/62 compared to WT (Fig. 1A), mainly as a result of a low concentration of the NAD(P)H pools in the ALDH single and double mutants compared to WT
Given that the oxidation of aldehydes by ALDHs generates reducing equivalents in the form of NADH or NADPH, we investigated how the ALDHs may influence the cellular redox homeostasis

Summary

Introduction

To investigate whether the ALDHs influence the cellular redox, we examined their contribution to the pyridine nucleotide NAD(P) and NAD(P)H pools by using a double T-DNA insertion mutant (KO6/62) of A. thaliana that is defective in the ALDH7B4 and ALDH3I1 genes. We measured the levels of the oxidized and reduced forms of the pyridine nucleotides NAD, NADP, NADH, and NADPH in leaves of six-week-old plants (Table 1).

Results

Conclusion