Cytokinins (CKs) function in plant development and during stress responses, but their role in drought tolerance in wheat is unknown. In the present study, 24 isopentenyltransferase (IPT) genes, encoding rate-limiting enzymes in CK biosynthesis were identified in the wheat genome. The chromosomal locations and structures of the genes, protein properties, and phylogenetic relationships were characterized. ATP/ADP TaIPT genes showed tissue-specific expression. TaIPT2, TaIPT7, and TaIPT8 expression was rapidly induced by 0.5–1 h drought treatments, which decreased to low levels after 2 h drought treatment, as did most other TaIPT genes. TaIPT8-5a/5b/5d triple mutants showed decreased levels of tZ-type CK under normal and drought conditions and reduced drought tolerance, which, however, did not manifest as phenotype alterations. By contrast, transgenic wheat plants with drought-induced TaIPT8 showed increased drought tolerance. Our study provides a foundation for further investigation of TaIPT genes and novel insights into the role of CKs in the drought response of wheat.

NAC family transcription factors (TFs) are important regulators in plant development and stress responses. However, the biological functions of NAC TFs in wheat are rarely studied. In this study, 43 putative drought-induced NAC genes were identified from de novo transcriptome sequencing data of wheat following drought treatment. Twelve wheat NACs along with ten known stress-related NACs from Arabidopsis and rice were clustered into Group II based on a phylogenetic analysis. TaNAC48, which showed a higher and constitutive expression level in Group II, was selected for further investigation. TaNAC48 transcript was up-regulated by drought, PEG, H₂O₂ and abscisic acid (ABA) treatment and encoded a nuclear localized protein. Overexpression of TaNAC48 significantly promoted drought tolerance with increased proline content, and decreased rates of water loss, malondialdehyde (MDA), H₂O₂ and O₂⁻ content. Root length and a stomatal aperture assay confirmed that TaNAC48-overexpression plants increased sensitivity to ABA. Electrophoretic mobility shift assay (EMSA) and luciferase reporter analysis indicated that TaAREB3 could bind to a cis-acting ABA-responsive element (ABRE) on TaNAC48 promoter and activate the expression of TaNAC48. These results suggest that TaNAC48 is essential in mediating crosstalk between the ABA signaling pathway and drought stress responses in wheat.

The engineering of plants with enhanced tolerance to abiotic stresses typically involves complex multigene networks and may therefore have a greater potential to introduce unintended effects than the genetic modification for simple monogenic traits. For this reason, it is essential to study the unintended effects in transgenic plants engineered for stress tolerance. We selected drought- and salt-tolerant transgenic wheat overexpressing the transcription factor, GmDREB1, to investigate unintended pleiotropic effects using RNA-seq analysis. We compared the transcriptome alteration of transgenic plants with that of wild-type plants subjected to salt stress as a control. We found that GmDREB1 overexpression had a minimal impact on gene expression under normal conditions. GmDREB1 overexpression resulted in transcriptional reprogramming of the salt response, but many of the genes with differential expression are known to mitigate salt stress and contribute incrementally to the enhanced stress tolerance of transgenic wheat. GmDREB1 overexpression did not activate unintended gene networks with respect to gene expression in the roots of transgenic wheat. This work is important for establishing a method of detecting unintended effects of genetic engineering and the safety of such traits with the development of marketable transgenic crops in the near future.

The transcription factor dehydration-responsive element binding protein (DREB) is able to improve tolerance to abiotic stress in plants by regulating the expression of downstream genes involved in environmental stress resistance. The objectives of this study were to evaluate the salt tolerance of GmDREB1 transgenic wheat (Triticum aestivum L.) and to evaluate its physiological and protein responses to salt stress. Compared with the wild type, the transgenic lines overexpressing GmDREB1 showed longer coleoptiles and radicles and a greater radicle number at the germination stage, as well as greater root length, fresh weight, and tiller number per plant at the seedling stage. The yield-related traits of transgenic lines were also improved compared with the wild type, indicating enhanced salt tolerance in transgenic lines overexpressing GmDREB1. Proteomics analysis revealed that osmotic- and oxidative-stress-related proteins were up-regulated in transgenic wheat leaves under salt stress conditions. Transgenic wheat had higher levels of proline and betaine and lower levels of malondialdehyde and relative electrolyte leakage than the wild type. These results suggest that GmDREB1 regulates the expression of osmotic- and oxidative-stress-related proteins that reduce the occurrence of cell injury caused by high salinity, thus improving the salt tolerance of transgenic wheat.

Aphids are major agricultural pests that cause significant yield losses in crop plants each year. (E)-β-farnesene (EβF) is the main or only component of an alarm pheromone involved in chemical communication within aphid species and particularly in the avoidance of predation. EβF also occurs in the essential oil of some plant species, and is catalyzed by EβF synthase. By using oligonucleotide primers designed from the known sequence of an EβF synthase gene from black peppermint (Mentha×piperita), two cDNA sequences, MaβFS1 and MaβFS2, were isolated from Asian peppermint (Mentha asiatica). Expression pattern analysis showed that the MaβFS1 gene exhibited higher expression in flowers than in roots, stems and leaves at the transcriptional level. Overexpression of MaβFS1 in tobacco plants resulted in emission of pure EβF ranging from 2.62 to 4.85 ng d⁻¹ g⁻¹ of fresh tissue. Tritrophic interactions involving peach aphids (Myzus persicae), and predatory lacewing (Chrysopa septempunctata) larvae demonstrated that transgenic tobacco expressing MaβFS1 had lower aphid infestation. This result suggested that the EβF synthase gene from Asian peppermint could be a good candidate for genetic engineering of agriculturally important crop plants.