The Overexpression of a Transcription Factor Gene VbWRKY32 Enhances the Cold Tolerance in Verbena bonariensis

Abstract

Cold stress poses a serious threat to the survival and bloom of Verbena bonariensis. The enhancement of the cold tolerance of V. bonariensis is the central concern of our research. The WRKY transcription factor (TF) family was paid great attention to in the field of abiotic stress. The VbWRKY32 gene was obtained from V. bonariensis. The VbWRKY32 predicted protein contained two typical WRKY domains and two C2H2 zinc-finger motifs. Under cold stress, VbWRKY32 in leaves was more greatly induced than that in stems and roots. The overexpression (OE) in V. bonariensis increased cold tolerance compared with wild-type (WT). Under cold stress, the OE lines possessed showed greater recovery after cold-treatment restoration ratios, proline content, soluble sugar content, and activities of antioxidant enzymes than WT; the relative electrolyte conductivity (EL), the accumulation of malondialdehyde (MDA), hydrogen peroxide (H 2 O 2), and superoxide anion (O 2 −) are lower in OE lines than that in WT. In addition, a series of cold-response genes of OE lines were compared with WT. The results revealed that VbWRKY32 worked as a positive regulator by up-regulating transcription levels of cold-responsive genes. The genes above can contribute to the elevation of antioxidant activities, maintain the membrane stability, and raise osmotic regulation ability, leading to the enhancement of the survival capacity under cold stress. According to this work, VbWRKY32 could serve as an essential gene to confer enhanced cold tolerance in plants.

Function and Mechanism of WRKY Transcription Factors in Abiotic Stress Responses of Plants

“…WRKY TFs play a role in the stress response through different signal transduction pathways. For example, in Verbena bonariensis, VbWRKY32 as a positive regulator, upregulates the transcriptional level of cold response genes, which increases the antioxidant activity, maintains membrane stability, and enhances osmotic regulation ability, thereby improving the survival ability under cold stress [74]. The BcWRKY46 gene of Brassica campestris is strongly induced by low temperature and ABA, activating related genes in the ABA signaling pathway to improve the low-temperature tolerance of plants [59].…”

C2H2 Zinc Finger Proteins Response to Abiotic Stress in Plants

“…Recently, many C2H2-type zinc finger proteins were reported and studied not only in model plants (such as Arabidopsis , cotton, wheat, soybean and rice), but also in economic crops (tomato, cucumber, potato, apple and tobacco) [ 22 , 23 , 24 , 25 , 27 , 28 , 96 , 97 ]. For example, OsDRZ1 (drought-responsive zinc finger protein 1) positively regulates stress tolerance through the ROS scavenging system in Oryza sativa [ 95 ].…”

Integrating transcriptome and metabolome analyses of the response to cold stress in pumpkin (Cucurbita maxima)

“…And a set of WRKY genes were also found to be chilling-regulated in indica rice, of which 12 were commonly induced, 22 were exclusively up-regulated in cold susceptible variety and 18 were exclusively up-regulated in cold tolerant variety genotype [ 63 ]. Moreover, the roles of VaWRKY12 from Vitis amurensis in cold stress tolerance were confirmed through its ectopic overexpression in Arabidopsis and grapevine [ 64 ]. A VbWRKY32 in the seedling stage of Verbena bonariensis upregulates the transcriptional level of cold response genes, which increases the antioxidant enzyme activities and the contents of osmotic adjustment substance, thereby improving the survival ability under cold stress [ 65 ].…”