Expression of the Pyrus sinkiangensis HD-Zip I transcription factor PsHB7 and PsHB12 in hybrid Broussonetia papyrifera regulates its natural overwintering

HD-Zip transcription factors are unique to higher plants and contributes to abiotic stress tolerance. In this study, PsHB7 and PsHB12 from the phloem of Pyrus sinkiangensis were cloned and transferred into hybrid Broussonetia papyrifera to evaluate their functions in cold acclimation. PsHB7 and PsHB12 expression in B. papyrifera decreased the rate of water loss, thereby affecting the overall physiology of the plants. After ABA treatment, increases in the water content and soluble protein levels in transgenic lines conferred enhanced freeze resistance. Comprehensive analyses of anti-freezing performance using logistic regression and membership functions yielded consistent results with the physiological experimental data. Furthermore, after natural overwintering, the transgenic lines exhibited less frost damage and the germination time was 20 days earlier than that of the wildtype plants. These results suggest that PsHB7 and PsHB12 play a key role in the negative feedback regulation of ABA signaling, which can balance cellular water efflux and the accumulation of dehydrated proteins.