Characterization of Aldehyde Oxidase (AO) Genes Involved in the Accumulation of Carotenoid Pigments in Wheat Grain

Abstract

Aldehyde Oxidase (AO) enzyme (EC 1.2.3.1) catalyzes the final steps of carotenoid catabolism and it is a key enzyme in the abscisic acid (ABA) biosynthesis. AO isoforms are located in the cytosolic compartment of tissues in many plants, where induce the oxidation of aldehydes into carboxylic acid, and in addition, catalyze the hydroxylation of some heterocycles. The goal of the present study was to characterize the <i>AO</i> genes involved in the accumulation of carotenoid pigments in wheat grain, an important quantitative trait controlled by multiple genes. The cDNAs corresponding to the four <i>AO</i> isoforms from <i>Arabidopsis thaliana</i> and five <i>AO</i> isoforms from <i>Brachypodium distachyon</i> were used as query in 454 sequence assemblies data for <i>Triticum aestivum</i> cv. Chinese Spring (https://urgi.versailles.inra.fr/blast/blast.php) to obtain the partial or whole orthologous wheat <i>AO</i> sequences. Three wheat isoforms, designated <i>AO1, AO2</i>, and <i>AO3</i> were located on the chromosome groups 2, 5, and 7, respectively, and mapped on two consensus wheat maps by SNP markers located within the <i>AO</i> gene sequences. To validate the possible relationships between <i>AO3</i> genes and carotenoid accumulation in wheat, the expression levels of <i>AO-A3</i> and <i>AO-B3</i> gene were determined during the kernel maturation stage of two durum wheat cultivars, Ciccio and Svevo, characterized by a low and high carotenoid content, respectively. Different <i>AO-A3</i> gene expression values were observed between the two cultivars indicating that the <i>AO-A3</i> allele present in Ciccio was more active in carotenoid degradation. A gene marker was developed and can be used for marker-assisted selection in wheat breeding programs.