IMPROVING FUSARIUM VERTICILLIOIDES RESISTANCE IN MAIZE THROUGH A LOX GENE OVEREXPRESSION

Fusarium verticillioides (Fv) is a prominent pathogen in cereal crops, leading to stalk and ear rot in maize. This pathogen significantly reduces crop yields and poses a threat to food safety by producing fumonisins, a type of secondary metabolites. Numerous studies have aimed to discover maize genes that contribute to resistance against Fv infection and the accumulation of fumonisins. Among these genes, lipoxygenases (ZmLOXs) are crucial in the plant's defense mechanisms against pathogens. It is welldocumented that lipid interactions between host and pathogen play an important role in the disease process. Previous RNA-Seq experiments demonstrated increased expression of ZmLOX genes in maize genotypes that exhibit resistance, and gene knock-out resulted in enhanced susceptibility against the pathogen. In this study, the overexpression of ZmLOX4 was carried out to investigate the possible implication of the gene in the resistance mechanisms against Fv. ZmLOX4 gene was then cloned under the promoter pCsVMV using the vector L1781. This construct was introduced into maize A188 line through Agrobacterium tumefaciens-mediated transformation. As a result, mutants from two separate transformation events were generated. For each event, T2 plants were genotyped to identify those that were homozygous for the mutation. Two homozygous lots of the transgenic lines overexpressing ZmLOX4 (hereby named LOX4OE) and A188 were chosen to perform disease assay, RNA-Seq, lipidomic, hormonal and fumonisin accumulation analysis. The RNA-Seq analysis was carried out on seeds of the three genotypes collected at 3 days post inoculation (dpi) with Fv and mockinoculated. More than 578 and 433 million of bp paired-end reads were generated for mock and inoculated plants, respectively. Pairwise differential expression analysis was performed between the transcriptomes of the three genotypes and inoculated vs. mock-inoculated transcriptomes revealing a total number of 10,677 differentially expressed genes (DEGs). Moreover, the number of counts per million (CPM) of ZmLOX4 gene was 12,361 and 14,435 for the two LOX4OE events, respectively, whereas only 178 CPM were observed in A188. The results deriving from DEG functional annotation along with the determination of hormonal and lipid profiles are currently being analyzed to better clarify molecular processes undergoing in maize upon Fv infection.