Overexpression of MpbHLH transcription factor, an encoding ICE1-like protein, enhances Foc TR4-resistance of Cavendish banana

Haochen Li,Chunhua Hu,Aifeng Xie,Shaoping Wu,Fangcheng Bi,Tao Dong,Chunyu Li,Guiming Deng,Weidi He,Huijun Gao,Ou Sheng,Ganjun Yi,Qiao-Song Yang,Tongxin Dou

doi:10.1016/j.scienta.2021.110590

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.

Highlights

Fusarium wilt is a worldwide problem that restrains the development of banana industry
The full-length cDNA of MpbHLH was isolated from leaves of the Dajiao plantlets (Figure S1)
The MpbHLH amino acid sequence was compared with different species of monocotyledonous and dicotyledonous plants, and the phylogenetic tree analysis reveals that MpbHLH is clearly clustered with monocotyledonous plants (Figure 2B)

Summary

Introduction

Fusarium wilt is a worldwide problem that restrains the development of banana industry. Isolation and identification of resistance genes is significance for the selection of disease resistant varieties, and important for banana molecular breeding. Compared to other food crops, the yield and productivity of banana are adversely constrained by several key biotic and abiotic stresses, chief among these is Fusarium wilt [3,4]. Development of Fusarium wilt-resistant banana faces challenges of sexual reproduction barriers such as high sterility, complex genetic background, polypoid nature, and parthenogenesis, making it extremely difficult to develop new disease-resistant bananas via cross-breeding [8,9]. Researchers have invested a lot of efforts in cultivating new disease-resistant banana germplasm by the transformation of disease-resistant genes, and have made certain progress. Mazizh et al (2007) introduced soybean β-1-3glucanase gene into the banana, proving that the transgenic plant had a certain resistance to Foc Race 1 [10]; the overexpression of PhDef and PhDef, two antimicrobial peptide genes of Petunia, could significantly improve banana’s resistance to Foc TR4 [11]; Mohandasa et al

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Conclusion