Mechanisms of BpTT2 overexpression in enhancing cadmium tolerence of Broussonetia papyrifera

The development of cadmium-resistant plants has become a promising green biotechnology in the field of soil heavy metal remediation due to its advantages of low cost, wide adaptability and no secondary pollutants, it is the key to realize the application of this technology. In this study, we clarified the role of BpTT2 in Broussonetia papyrifera in response to Cd stress. Under the induction of 500 μmol/L CdCl₂, the anti-Cd ability of BpTT2-overexpressed B. papyrifera was enhanced, and the accumulation of Cd was significantly reduced (P < 0.05). The plant height, biomass and total chlorophyll content of BpTT2-overexpressed B. papyrifera were significantly higher than those of non-transgenic lines (P < 0.001). Moreover, more substances related to ROS accumulation, such as MDA and H₂O₂, were detected in non-transgenic lines. Transcriptome sequencing showed that the AUX/IAA signal transduction gene (ARF5), ABA signal transduction genes (PP2C and SNRK2), protein kinase-related genes (PHOT1, WAKL4, PK1 and MPK3), ROS accumulation-related genes (RbohD and CAT1), and TFs family genes highly sensitive to Cd stress were significantly up-regulated in BpTT2-overexpressed B. papyrifera (P < 0.01). Notably, these genes regulate multiple signaling cascades simultaneously in the same protein family, which not only regulate plant signal transduction pathways, but also participate in the scavenging ROS and the feedback regulation of H₂O₂ signal. This study confirmed that the overexpression of BpTT2 can enhance the remediation effect of B. papyrifera on soil Cd pollution, which has important significance for better utilization of phytoremediation technology to treat heavy metal pollution.