AtMYB44 regulates resistance to the green peach aphid and diamondback moth by activating EIN2‐affected defences in Arabidopsis

Abstract Recently we showed that the transcription activator A t MYB 44 regulates expression of EIN2 , a gene essential for ethylene signalling and insect resistance, in A rabidopsis thaliana ( A rabidopsis ). To link the transactivation with insect resistance, we investigated the wild‐type and atmyb44 mutant plants, genetically C omplemented atmyb44 ( Catmyb44 ) and AtMYB44 ‐ O verexpression T ransgenic A rabidopsis ( MYB44OTA ). We found that AtMYB44 played a critical role in A rabidopsis resistance to the phloem‐feeding generalist green peach aphid ( M yzus persicae S ulzer) and leaf‐chewing specialist caterpillar diamondback moth ( P lutella xylostella L .). AtMYB44 was required not only for the development of constitutive resistance but also for the induction of resistance by both herbivorous insects. Levels of constitutive and herbivore‐induced resistance were consistent with corresponding amounts of the At MYB 44 protein constitutively produced in MYB44OTA and induced by herbivory in Catmyb44 . In both cases, A t MYB 44 promoted EIN2 expression to a greater extent in MYB44OTA than in Catmyb44 . However, A t MYB 44‐promoted EIN2 expression was arrested with reduced resistance levels in the EIN2 ‐deficient A rabidopsis mutant ein2‐1 and the MYB44OTA ein2‐1 hybrid. In the different plant genotypes, only MYB44OTA constitutively displayed phloem‐based defences, which are specific to phloem‐feeding insects, and robust expression of genes involved in the biosynthesis of glucosinolates, which are the secondary plant metabolites known as deterrents to generalist herbivores. Phloem‐based defences and glucosinolate‐related gene expression were not detected in ein2‐1 and MYB44OTA ein2‐1 . These results establish a genetic connection between the regulatory role of AtMYB44 in EIN2 expression and the development of A rabidopsis resistance to insects.