Comprehensive Analysis of the DnaJ/HSP40 Gene Family in Maize (Zea mays L.) Reveals that ZmDnaJ96 Enhances Abiotic Stress Tolerance

DnaJ, or heat shock protein 40 (HSP40), is a conserved protein that functions as a molecular chaperone with a strong cytoprotective effect, participating in plant signal transduction, growth, development, and the response to heat stress and other adverse environmental conditions. Although functional characteristics of DnaJ/HSP40 have been described in several plant species, the underlying mechanisms are not completely understood. In this study, 99 putative maize (Zea mays L.) DnaJ genes (ZmDnaJ01–99) randomly distributed on 10 chromosomes were identified in the whole genome using bioinformatics approaches and classified into three groups according to protein structure. The conservation of the gene structure was closely related to the evolutionary tree. Collinearity analysis of DnaJ family genes among species revealed a close evolutionary relationship between maize and sorghum. Transposon analysis revealed helitrons inserted in 49 ZmDnaJs. Multiple stress-related cis-elements were found in the promoter regions of ZmDnaJ genes, suggesting a role in gene expression regulation in response to abiotic stress. The co-expression network screened 12 ZmDnaJ genes that could be induced by stress (drought, high temperature, and salt) and regulated by abscisic acid. ZmDnaJ96 overexpression increased antioxidant enzyme activity and reduced the damage caused by drought and high-temperature stress in Arabidopsis chloroplasts. Virus-induced silencing of ZmDnaJ96 reduced drought and heat tolerance in maize by reducing antioxidant enzyme activity. These results provide genetic resources for maize stress resistance molecular breeding, enhance knowledge of DnaJ gene function in maize, and offer a solid foundation for further in-depth study of the relationship between maize DnaJ/HSP40 members.