ZmPP2C45 and ZmBELL4 suppress maize biochemical defense against insect herbivores

PP2Cs represent the largest gene family of protein phosphatases. Current research has predominantly focused on the regulation of the PP2C.A family in the abscisic acid (ABA) signaling pathway. However, there is currently no documented research regarding the involvement of PP2Cs in plant responses to biotic stressors. In this study, we found that maize (Zea may) ZmPP2C45 is an essential but insufficient negative regulator of benzoxazinoids. Since BZXs are important defensive metabolites against insect herbivores, we hypothesized that the genetic knock-out of ZmPP2C45 could affect the performance of insect herbivores on these plants.To further investigate how ZmPP2C45 depleted BZX contents, we performed a comparative transcriptomics analysis on the Zmpp2c45 mutants and the wildtype control. As a result, 789 genes were found significantly up-regulated in the mutant plants, whereas 198 genes were down-regulated. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses revealed that BZX biosynthesis-related genes were over-represented among the up-regulated genes in the Zmpp2c45 plants Maize inbred line KN5585 was used as the genetic background for genome editing of ZmPP2C45. The expression level were tested between maize inbred line KN5585 (WT) and ZmPP2C45 knock-out line. Leaves of two-week-old maize seedlings were used for RNAseq analyses