Abstract
The application of drought stress-regulating transcription factors (TFs) offers a credible way to improve drought tolerance in plants. However, many drought resistant TFs always showed unintended adverse effects on plant growth or other traits. Few studies have been conducted in trees to evaluate and overcome the pleiotropic effects of drought tolerance TFs. Here, we report the dose-dependent effect of the Limonium bicolor LbDREB6 gene on its overexpression in Populus ussurensis. High- and moderate-level overexpression of LbDREB6 significantly increased drought tolerance in a dose-dependent manner. However, the OE18 plants showed stunted growth under normal conditions, but they were also more sensitive to Marssonina brunnea infection than wild type (WT) and OE14 plants. While, OE14 showed normal growth, the pathogen tolerance of them was not significantly different from WT. Many stress-responsive genes were up-regulated in OE18 and OE14 compared to WT, especially for OE18 plants. Meanwhile, more pathogen tolerance related genes were down-regulated in OE18 compared to OE14 and WT plants. We achieved improved drought tolerance by adjusting the increased levels of exogenous DREB genes to avoid the occurrence of growth reduction and reduced disease tolerance.
Highlights
Drought is among the most serious environmental stressors resulting in substantial damage annually to the global agricultural and forestry industries (Kudo et al, 2017)
The increased ratio of OE18 plant height was higher than that of wild type (WT) plants (Supplementary Figure 3). These results demonstrated that high-level overexpression of LbDREB6 decreased growth rate, probably by inhibiting gibberellic acid (GA) synthesis, while moderate overexpression of LbDREB6 did not change the normal growth of transgenic P. ussuriensis
We found that multiple pattern recognition receptors that participate in the pattern triggered immunity (PTI) system, especially EF-Tu receptors (ETRs), were differentially expressed in the OE18 line, in which they were largely down-regulated compared to OE14 and WT plants
Summary
Drought is among the most serious environmental stressors resulting in substantial damage annually to the global agricultural and forestry industries (Kudo et al, 2017). Improving drought tolerance of plants is urgently needed to stabilize the global productivity of crops. The application of TFs to improve drought tolerance frequently comes at the cost of introducing undesired phenotypes, such as dwarfism, decreased pathogen tolerance, and decreased grain yield (Lata and Prasad, 2011; Bhargava and Sawant, 2013; Cabello et al, 2014; Shavrukov et al, 2016). These negative effects constrain the practical utilization of drought-resistant transgenic plants based
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