Identification and Evolution Analysis of the JAZ Gene Family in Maize

Background: Jasmonates (JAs) are important for plants to coordinate growth, reproduction, and defense responses. In JA signaling, jasmonate ZIM-domain (JAZ) proteins serve as master regulators at the initial stage of herbivores attacks. Although discovered in many plant species, little in-depth characterization of JAZ gene expression has been reported in the agronomically important crop, maize (Zea mays L.). Results: In this study 16 JAZ genes from the maize genome were identified and classified. Phylogenetic analyses were performed from maize, rice, sorghum, Brachypodium, and Arabidopsis using deduced protein sequences, total six clades were proposed and conservation was observed in each group, such as similar gene exon/intron structures. Synteny analysis across four monocots indicated these JAZ gene families had a common ancestor, and duplication events in maize genome may drive the expansion of JAZ gene family, including genome-wide duplication (GWD), transposon, and/or tandem duplication. Strong purifying selection acted on all JAZ genes except those in group 4, which were under neutral selection. Further, we cloned three paralogous JAZ gene pairs from two maize inbreds differing in JA levels and insect resistance, and gene polymorphisms were observed between two inbreds. Conclusions: Here we analyzed the composition and evolution of JAZ genes in maize with three other monocot plants. Extensive phylogenetic and synteny analysis revealed the expansion and selection fate of maize JAZ. This is the first study comparing the difference between two inbreds, and we propose genotype-specific JAZ gene expression might be present in maize plants. Since genetic redundancy in JAZ gene family hampers our understanding of their role in response to specific elicitors, we hope this research could be pertinent to elucidating the defensive responses in plants.