Functional analysis of sweet cherry PavbHLH106 in the regulation of cold stress.

Sweet cherry PavbHLH106 was up-regulated under cold induction and overexpressed to enhance the cold resistance in tobacco by mediating the scavenging of ROS through increasing of antioxidant enzyme activity. Sweet cherry (Prunus avium L.) is an economically important fruit. Chilling requirements are critical during dormancy, but abnormally low temperatures unfavorably affect fruit growth and development. Differences were found in the transcript level of PavbHLH106 under salt, dehydration, and low-temperature treatments, especially in response to cold stress, suggesting that this gene is involved in the regulation of different abiotic stresses. PavbHLH106 is homologous to Arabidopsis thaliana AtbHLH106 with a conserved bHLH domain, and transient expression in tobacco suggests that the protein is localized in the nucleus and has transcriptional activity in yeast. The PavbHLH106 overexpression in tobacco resulted in weaker electrolyte leakages, lower malondialdehyde, and higher proline content than the wild type at low-temperature treatment. Reactive oxygen species accumulation was significantly reduced in the overexpressed lines, negatively correlated with the antioxidant enzyme activity. In addition, overexpression of PavbHLH106 delayed the germination of tobacco seeds and promoted plant growth. Resistance-related genes were expressed more in the overexpressed plants compared to the wild type. PavbHLH106 bound to the PavACO promoter in yeast and potentially interacted with a bHLH162-like transcription factor. These results indicate that PavbHLH106 has various functions and is particularly active in controlling low-temperature stress.