Molecular Characterization of Acyl-CoA Oxidase (ACX) Family Genes in Maize Reveals Their Role in Disease Resistance.

BACKGROUND

Acyl-CoA oxidase (ACX), a ubiquitous eukaryotic enzyme, catalyzes the initial steps of fatty acid β oxidation and plays an important role in the biosynthesis of jasmonic acid (JA). At present, no studies have been reported on ACX family members of maize and their function in disease resistance.

OBJECTIVES

This study aims to lay a foundation for clarifying the functions of ACX family genes in maize growth, development, and stress response by conducting a genome-wide identification of ACX family genes in maize, analyzing the expression characteristics of these genes in maize growth and development, hormone treatment and response to biotic and abiotic stresses, and exploring the functions of key genes in the maize disease resistance process through the use of mutants.

METHODS

ProtParam, TBtools, MEME, MEGA, and IBS tools were used to identify maize ACX family genes and analyze the physicochemical properties of their proteins, chromosome location, phylogenetic relationships among family members, conserved domains, conserved motifs, and cis-acting elements. Meanwhile, the expression patterns of maize ACX family genes in different tissues and their expression patterns under abiotic and biotic stresses were studied by using the data from the maize GDB database and qRT-PCR technology. Moreover, the mutants of , , , and genes were obtained, and the disease resistance of the mutants was detected to further determine the functions of ACX genes in the maize disease resistance process. This study identified maize ACX family genes using bioinformatics methods.

RESULTS

We discovered that six ACX genes in the maize genome are distributed across four different chromosomes. Cluster analysis further classified these genes into three subfamilies. All maize ACX genes possess a conserved ACOX domain, and their promoter regions are enriched with cis-acting elements associated with heat stress and the plant hormone response. Under various tissue, biotic, and abiotic stress conditions, as well as treatments with methyl jasmonate (MeJA) and salicylic acid (SA), the expression levels of maize ACX family genes exhibited significant differences. Notably, the expression levels of , , , and were significantly up-regulated following stress and pathogen infection, suggesting their involvement in maize growth, development, and disease resistance. To elucidate the function of these genes in maize disease resistance, the resistance of , , , and mutants to , , and were further examined. The results revealed that compared to the wild-type B73, the lesion area of the mutants was significantly increased after inoculation with pathogens. This directly demonstrated the crucial role of these genes in maize resistance to , , and .

CONCLUSIONS

In summary, this study systematically identified maize ACX family genes, and thoroughly investigated their expression patterns and functions in maize disease resistance. Our findings provide valuable insights into the comprehensive understanding of the function and mechanism of maize ACX family genes.