Abstract
The DREB transcription factors regulate multiple stress response genes, and are therefore useful for molecular plant breeding. AhDREB, a stress-inducible gene, was isolated from Atriplex hortensis L. and introduced into Populus tomentosa Carrière under the control of the CaMV35S promoter. Under salt stress, the chlorophyll content and net photosynthetic rate were higher in transgenic lines than in the wild type (WT). Moreover, the rate of electrolyte penetration (REC) was lower in the transgenic lines. Additional analyses revealed that the AhDREB transgenic plants generally displayed lower malondialdehyde (MDA) activity but higher superoxide dismutase (SOD) and peroxidase (POD) activities and proline content than the WT under salt stress. RNA sequencing indicated that AhDREB could enhance tolerance to salt by activating various downstream genes in the transgenic plants. Furthermore, no growth inhibition was detected in transgenic plants expressing AhDREB driven by the constitutive CaMV35S promoter. The transcriptome showed 165 and 52 differentially expressed genes in transgenic plants under stress and non-stress conditions, respectively, among which no significant metabolic pathway was enriched and no unintended effects have yet been identified. Together, these results suggest that AhDREB may be a good candidate gene for increasing salt tolerance in transgenic poplar breeding.
Highlights
Populus tomentosa Carr. (P. tomentosa) is native to China, where it is mainly distributed in 10 provinces in the northern part of the country
We found a number of reactive oxygen species (ROS)-responsive genes were up-regulated in transgenic poplars suffering from salt stress, indicating that AhDREB expression may modulate activity in ROS-scavenging pathways
Mutation of wall-associated kinase 2 in Arabidopsis led to dependence on sugars and salts for seedling growth. These results suggest that AhDREB may influence the growth of receptor plants by regulating some growth-associated genes, despite significant growth reduction not being observed in AhDREB transgenic lines
Summary
Populus tomentosa Carr. (P. tomentosa) is native to China, where it is mainly distributed in 10 provinces in the northern part of the country. One type of TF, DREB proteins of the ERF subfamily, can improve salt stress tolerance in plants These proteins function through interaction with a dehydration-responsive cis-element found in the core A/GCCGAC sequence of the promoter region of several genes that are induced in response to salt and other abiotic stresses [13]. Due to their ability to regulate a large number of downstream stress-responsive genes, these genes have the potential for improving stress tolerance in transgenic plant breeding [14,15,16]. Improving the salinity tolerance of the plants through overexpression of DREBs has been accomplished in Arabidopsis, tobacco, rice, wheat, potato, soybean and many other plants
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