AAO2 impairment improves aldehyde detoxification by AAO3 in Arabidopsis leaves exposed to UVC or Rose Bengal

Abstract

AbstractAmong the three active aldehyde oxidases inArabidopsis thalianaleaves (AAO1-3), AAO3, which catalyzes the oxidation of abscisic-aldehyde to abscisic-acid, was shown recently to function as a reactive aldehyde detoxifier. Notably,aao2KOmutants exhibited less senescence symptoms and lower aldehyde accumulation, such as acrolein, benzaldehyde, and HNE than in wild-type leaves exposed to UV-C or Rose-Bengal. The effect of the absence of AAO2 expression on aldehyde detoxification by AAO3 and/or AAO1 was studied by comparing the response of wild-type plants to the response ofaao1Singlemutant,aao2KOmutants and single mutants ofaao3Ss. Notably,aao3Ssexhibited similar aldehyde accumulation and chlorophyll content toaao2KOtreated with UV-C or Rose-Bengal. In contrast, wild-type andaao1Sexhibited higher aldehyde accumulation that resulted in lower remaining chlorophyll than in aao2KOleaves, indicating that the absence of active AAO2 enhanced AAO3 detoxification activity inaao2KOmutants. In support of this notion, employing abscisic-aldehyde as a specific substrate marker for AAO3 activity revealed enhanced AAO3 activity inaao2KOandaao3Ssleaves compared to wild-type treated with UV-C or Rose Bengal. The similar abscisic acid level accumulated in leaves of unstressed or stressed genotypes indicates that aldehyde detoxification by AAO3 is the cause for better stress resistance inaao2KOmutants. Employing the sulfuration process (known to activate aldehyde oxidases) in wild-type,aao2KO, andmolybdenum-cofactor sulfurase(aba3-1) mutant plants revealed that the active AAO2 in WT employs sulfuration processes essential for AAO3 activity level, resulting in the lower AAO3 activity in WT than AAO3 activity inaao2KO.