Simultaneous Overexpression of the HhERF2 and PeDREB2a Genes Enhanced Tolerances to Salt and Drought in Transgenic Cotton

A desert-grown Halimodendron halodendron ethylene-responsive element binding factor gene (HhERF2), which encodes a 245 amino acids protein containing a conserved AP2/EREBP domain, was isolated through the rapid amplification cDNA end (RACE) method. Sequence and phylogenetic analysis indicated that HhERF2 was classified into the B-2 group of ERF subfamily. Semiquantitative RT-PCR showed that HhERF2 was greatly induced by treatments with high-salt, drought and low temperature in H. halodendron seedlings. The expression vector containing HhERF2 and Populus euphratica dehydration- responsive element binding protein (PeDREB2a) genes driven by rd29A promoter was constructed and transferred into cotton (Gossypium hirsutum L.) by non-tissue culture Agrobacterium-mediated genetic transformation system. The transformation and expression of HhERF2 and PeDREB2a were identified by PCR and RT-PCR. Analyses of physiological function indicated that transgenic cottons had improved seeds germination, tolerance to drought and highsalt stresses. Agronomic evaluation in the field exhibited that transgenic lines presented a dwarf phenotype and improved further in the yield and characters. These results demonstrated that overexpressed both HhERF2 and PeDREB2a transcription factor genes in cotton induced elevated tolerance to drought and high-salt stresses.