The γ-clade HD-Zip I transcription factor MdHB-7 regulates salt tolerance in transgenic apple (Malus domestica)

• Published in: Plant and soil 2021-06, Vol.463 (1-2), p.509-522
• Main Authors: Zhao, Shuang, Gao, Hanbing, Jia, Xumei, Li, Xuewen, Mao, Ke, Ma, Fengwang
• Format: Article
• Language: English
• Subjects: Abiotic stress; Agricultural production; Antioxidants; Apples; Biomedical and Life Sciences; Damage accumulation; Detoxification; Ecology; Extreme values; Fruits; Gene expression; Homeostasis; Hydroponics; Life Sciences; Malus domestica; Photosynthesis; Plant growth; Plant Physiology; Plant Sciences; Reactive oxygen species; Regular Article; RNA-mediated interference; Salinity; Salinity effects; Salinity tolerance; Salt tolerance; Sodium chloride; Soil Science & Conservation; Transcription factors; Transcriptomes; Transgenic plants
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1007/s11104-021-04918-9

Aims Salinity plays a crucial role in numerous environmental processes, with extreme concentrations resulting in the serious decline of global agricultural productivity. Plant-specific HD-Zip I transcription factors (TFs), particularly γ-clade HD-Zip I members, are key for the adaption of plants to various abiotic stresses. Our main purpose is to characterize the function of γ-clade HD-Zip I members in apple under salt stress. Methods GL-3 and transgenic plants were grown in a hydroponic system or in soil and exposed to the presence or absence of NaCl. Photosynthetic capacity, root damage, Na + and K + accumulation, reactive oxygen species (ROS) accumulation, and RNA-seq were investigated. Results MdHB-7 (γ-clade HD-Zip I TF) expression was induced by salt stress, particularly in the roots. We employed MdHB-7 overexpression and MdHB-7 RNAi transgenic apple plants for the treatments to explore the functions of MdHB-7 under salt stress. Results from the salt treatment and phenotypic evaluation revealed the enhancement of the salt tolerance of apple plants by the MdHB-7 expression. The overexpression of MdHB-7 reduced the salt stress-induced damage to root growth and vitality and maintained ion homeostasis. Moreover, the overexpression of MdHB-7 was observed to promote the detoxification of ROS. Transcriptome and qRT-PCR analysis demonstrate that MdHB-7 overexpression up-regulated the expression of antioxidant enzyme-related genes. MdHB-7 -mediated root vitality, antioxidant activity and ion homeostasis were impaired, resulting in MdHB-7 RNAi lines that were more sensitive to salt stress. Conclusions Our results demonstrate the key role of MdHB-7 as a salinity stress tolerance regulator in apple ( Malus domestica ).