Overexpression of Malus hupehensis MhSHN1 Gene Enhances Salt and Osmotic Stress Tolerance in Transgenic Tobacco Plants

Plant APETALA2/Ethylene-responsive element binding factor (AP2/ERF) transcription factor involved in various biological functions such as plant development, flower development, fruit and seed maturation, wounding, pathogen defense, high salty, drought, and so on. Here, we reported the function analysis of an AP2/ERF member, MhSHN1, from Malus hupehensis (Pamp.) Rehder. The MhSHN1 gene has a total of 1171 bp and consists of two exons of 81 and 531 bp, one intron of 559 bp. Phylogenetic analysis indicated MhSHN1 belongs to group V. The expression of MhSHN1 was highest in flower, then in seed and fruit, with low expression in root, leaves and stems. The MhSHN1 transcripts were barely affected by jasmonic acid (JA) and 1-aminocyclopropane- 1-carboxylic acid (ACC) within the first 48 h of treatment. Salicylic acid (SA) and abscisic acid (ABA) induce significantly the expression of MhSHN1. MhSHN1 mRNA levels were increased in response to mannitol and salt treatments. However, low temperature could not induce the expression of MhSHN1 gene. Overexpression of the MhSHN1 gene does not regulate seed germination but does positively regulate plant tolerance to salt and osmotic stresses at the stage of seed germination. These results showed the MhSHN1 gene play key role in resistance to mannitol and salt stresses in M. hupehensis.