The expression of MdBBX10 was significantly induced by different stresses and ABA treatments. Overexpression of MdBBX10 in Arabidopsis significantly enhanced abiotic stresses tolerance by ABA signalling. The roles of B-box domain(s) containing proteins (BBXs) in regulation of flowering and light morphogenesis of plants were intensively studied. However, the roles of plant BBXs in abiotic stresses are poorly understood. A B-box protein encoding gene from apple (MdBBX10) was found to be up-regulated from gene expression profile under salt stress. qRT-PCR analysis indicated that the expression of MdBBX10 was significantly induced by different stresses and exogenous abscisic acid (ABA) in apple roots and leaves. The β-glucuronidase activity driven by the promoter of MdBBX10 was also strongly induced by NaCl, H2O2, polyethylene glycol and exogenous ABA, which was consistent to the existence of rich cis-acting elements related to the abiotic stresses in the promoter sequence. Over-expression of MdBBX10 in Arabidopsis significantly enhanced tolerance to abiotic stresses, with higher germination ratio and longer length of roots than the wild type plants. Transgenic plants of over-expressing MdBBX10 lines were more sensitive to exogenous ABA than the wild type plants. Under abiotic stress treatments, the transcript levels of ABA- and stress-related genes were higher in MdBBX10-overexpressing plants than wild type plants. Over-expression of MdBBX10 could enhance plant's ability to scavenge reactive oxygen species (ROS) under stresses, which is correlated with the expression of ROS-scavenging genes. These results provided the evidences that MdBBX10 plays an important role in enhanced plant tolerance to abiotic stresses, which were involved in ABA-mediated response and ROS response.
Keywords: ABA signaling; Abiotic stresses; B-box protein; Stress tolerance.