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Crop production is the basis of agriculture in Kazakhstan. Soils in Kazakhstan suffer from molybdenum deficiency. Molybdenum deficiency in plants is characterized by the stunted growth, poor seed setting, fruit deformation and reduced plant resistance to diseases. Molybdenum catalyzes key steps in the metabolism of nitrogen, carbon and sulfur. It promotes the biosynthesis of the phytohormones of abscisic acid and indole-3-butyric acid. An increase in molybdenum concentration leads to an increase in aldehyde oxidase activity. Aldehyde oxidase generates hydrogen peroxide during viral infection; hydrogen peroxide triggers a hypersensitive response, strengthens cell walls and prevents the spread of viral infection. Molybdenum is biologically inactive until a special complex called molybdenum cofactor is formed. For the formation of the latter it is necessary for molybdenum to be in the state of molybdate anion. There are five known plant molybdoenzymes: aldehyde oxidase, sulfite oxidase, nitrate reductase, xanthine dehydrogenase and mitochondrial amidoxime resuctase. The aim of this work is to find the optimal concentration of molybdenum for aldehyde oxidase activation. The objectives of the conducted experiment are: - to apply an efficient and cost-effective method to replenish molybdenum deficiency in the experimental plant; - to demonstrate the effect of molybdenum on the development of virus infection of the infected plant. As a result, it was proved that with the increase of concentration from 0.1 mM to 1 mM, the activity of aldehyde oxidase increases, which contributes to the increase of seed germination. The optimal concentration for seed germination is 1 Mm molybdenum concentration. As the concentration of molybdenum increases, the resistance of adult plants to virus infection also increases. Thus, 1 mМ molybdenum concentration is optimal for seed germination and resistance to virus infection. [ABSTRACT FROM AUTHOR]

Among the three active aldehyde oxidases in Arabidopsis thaliana leaves (AAO1-3), AAO3, which catalyzes the oxidation of abscisic-aldehyde to abscisic-acid, was shown recently to function as a reactive aldehyde detoxifier. Notably, aao2KO mutants exhibited less senescence symptoms and lower aldehyde accumulation, such as acrolein, benzaldehyde, and 4-hydroxyl-2-nonenal (HNE) than in wild-type leaves exposed to UV-C or Rose-Bengal. The effect of AAO2 expression absence on aldehyde detoxification by AAO3 and/or AAO1 was studied by comparing the response of wild-type plants to the response of single-functioning aao1 mutant (aao1S), aao2KO mutants, and single-functioning aao3 mutants (aao3Ss). Notably, aao3Ss exhibited similar aldehyde accumulation and chlorophyll content to aao2KO treated with UV-C or Rose-Bengal. In contrast, wild-type and aao1S exhibited higher aldehyde accumulation that resulted in lower remaining chlorophyll than in aao2KO leaves, indicating that the absence of active AAO2 enhanced AAO3 detoxification activity in aao2KO mutants. In support of this notion, employing abscisic-aldehyde as a specific substrate marker for AAO3 activity revealed enhanced AAO3 activity in aao2KO and aao3Ss leaves 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 in aao2KO mutants. Employing the sulfuration process (known to activate aldehyde oxidases) in wild-type, aao2KO, and molybdenum-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 in aao2KO., (© 2024 The Author(s). The Plant Journal published by Society for Experimental Biology and John Wiley & Sons Ltd.)