SummarySalinity‐induced Na+ toxicity and oxidative stress hamper plant growth. Here, we showed that expression of the chrysanthemum CmHSFA4, a homologue of the heat‐shock factor AtHSFA4a, is inducible by salt and localizes to the nucleus. It is a transcription activator binding with HSE. Chrysanthemum overexpressing CmHSFA4 displayed enhanced salinity tolerance by limiting Na+ accumulation while maintaining K+ concentration, which is consistent with the up‐regulation of ion transporters CmSOS1 and CmHKT2. Additionally, the transgenic plants reduced H2O2 and O2 ∙− accumulation under salinity, which could be due to up‐regulation of ROS scavenger activities such as SOD, APX and CAT as well as CmHSP70, CmHSP90. Together, these results suggest that CmHSFA4 conferred salinity tolerance in chrysanthemum as a consequence of Na+/K+ ion and ROS homeostasis.

The family of DNA binding with one finger (DOF) transcription factors is plant specific, and these proteins contain a highly conserved domain (DOF domain) of 50-52 amino acids that includes a C2C2-type zinc finger motif at the N-terminus that is known to function in a number of plant processes. Here, we characterized 20 DOF genes in the important ornamental species chrysanthemum (Chrysanthemum morifolium) based on transcriptomic sequences. Phylogenetic analysis identified one pair of putative orthologous proteins in Arabidopsis and chrysanthemum and six pairs of paralogous proteins in chrysanthemum. Conserved motifs in the DOF proteins shared by Arabidopsis and chrysanthemum were analyzed using MEME. Bioinformatics analysis revealed that 13 CmDOFs could be targeted by 16 miRNA families. Moreover, we used 5' RLM-RACE to map the cleavage sites in CmDOF3, 15, and 21. The expression of these 20 genes in response to phytohormone treatments and abiotic stresses was characterized, and the expression patterns of six pairs of paralogous CmDOF genes were found to completely differ from one another, except for CmDOF6 and CmDOF7. This work will promote our research of the various functions of DOF gene family members in plant hormone and stress responses.

Chrysanthemum is frequently attacked by aphids, which greatly hinders the growth and ornamental value of this plant species. WRKY transcription factors play an important role in the response to biotic stresses such as pathogen and insect stresses. Here, chrysanthemum CmWRKY53 was cloned, and its expression was induced by aphid infestation. To verify the role of CmWRKY53 in resistance to aphids, CmWRKY53 transgenic chrysanthemum was generated. CmWRKY53 was found to mediate the susceptibility of chrysanthemum to aphids. The expression levels of secondary metabolite biosynthesis genes, such as peroxidase- and polyphenol oxidase-encoding genes, decreased in CmWRKY53-overexpressing (CmWRKY53-Oe) plants but dramatically increased in chimeric dominant repressor (CmWRKY53-SRDX) plants, suggesting that CmWRKY53 contributes to the susceptibility of chrysanthemum to aphids, possibly due to its role in the regulation of secondary metabolites.

No abstract