Overexpression of MdVQ37 reduces salt stress tolerance in Malus domestica
Qinglong Dong, Dingyue Duan, Jiale He, Wenqian Zheng, Dong Huang, Qian Wang, Jie Yang, Fengwang Ma and Ke Mao
Soil salinity is a major environmental threat to plant growth, development, and yield. Valine-glutamine (VQ) motif-containing proteins (VQ proteins) are involved in plant growth, development, and responses to abiotic and biotic stressors. However, the relationship between salt stress and VQ proteins has not been studied in horticultural crops. In this study, overexpression of the apple VQ family gene MdVQ37 markedly reduced the salt stress tolerance of transgenic apple plants. Physiological and biochemical assays suggested that the growth limitation, reactive oxygen species production, reduced photosynthetic capacity, and imbalance of ion homeostasis caused by salt stress were aggravated in transgenic lines compared with wild-type (WT) plants. In addition, compared with WT plants, MdVQ37-overexpressing transgenic apple lines showed significantly lower transcript levels of genes associated with ion homeostasis and encoding stress-related transcription factors under salt stress. In summary, we propose that MdVQ37 plays a negative role in the salt stress response of apple, primarily by affecting reactive oxygen species elimination, ion homeostasis, and expression levels of stress-related transcription factors.