Overexpression of MpbHLH Transcription Factor, An Encoding ICE-Like Protein, Enhances Foc TR4-Resistance of Cavendish Banana

Abstract Banana (Musa spp.) is an important tropical fruit with high economic value, however, Fusarium wilt disease is a critical factor affecting the sound development of the banana industry. Different cultivars of banana exhibit a high degree of genetic variability for resistance to Fusarium wilt. Compared with Cavendish banana (Musa spp. AAA group), Dajiao (Musa spp. ABB group) has superior disease resistance and provides an excellent test material for the isolation and characterization of disease resistance genes. In this study, a Dajiao candidate gene, MpbHLH (basic helix-loop-helix), an encoding ICE1-like protein transcription factor (TF), was cloned and characterized. Real-time quantitative PCR (qPCR) results revealed that MpbHLH transcript levels were strongly induced under cold treatment, salt, and dehydration. Overexpression of MpbHLH in Foc TR4-sensitive Cavendish banana showed that the transgenic lines had superior resistance to Fusarium wilt compared with the wild-type (WT). Proteomic analysis showed that phenylalanine ammonia lyase (PAL) and peroxidase (POD) were highly expressed in transgenic plants. Physiological experiments further revealed that transgenic plants, especially their roots, had high POD activity. Taken together, overexpression of MpbHLH in banana may extensively activate stress-related genes. In particular, the activity of POD increases the resistance of transgenic banana to Fusarium wilt by enhancing the reactive oxygen species (ROS) scavenging system of a transgenic plant.