Overexpression of Myrothamnus flabellifolia MfWRKY41 confers drought and salinity tolerance by enhancing root system and antioxidation ability in Arabidopsis

Authors: HUANG, ZHUO - Sichuan Agricultural University; SONG, LI - Sichuan Agricultural University; XIAO, Y - Sichuan Agricultural University; ZHONG, XIAOJUAN - Sichuan Agricultural University; WANG, JIATONG - Sichuan Agricultural University; XU, WENXIN - Sichuan Agricultural University; Jiang, Cai-Zhong

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/2022
Publication Date: 7/22/2022
Citation: Huang, Z., Song, L., Xiao, Y., Zhong, X., Wang, J., Xu, W., Jiang, C. 2022. Overexpression of Myrothamnus flabellifolia MfWRKY41 confers drought and salinity tolerance by enhancing root system and antioxidation ability in Arabidopsis. Frontiers in Plant Science. 13. Article 967352. https://doi.org/10.3389/fpls.2022.967352.
DOI: https://doi.org/10.3389/fpls.2022.967352

Interpretive Summary: As sessile organisms, plants are exposed to constantly varying environmental conditions and will inevitably encounter many abiotic stresses, for example, drought, water logging, heat, cold, salinity, and ultraviolet radiation. To adapt and counteract the negative effects of these abiotic stresses, plants have evolved complex molecular mechanisms involving signal perception, transduction and subsequent protective responses via a series of gene expressions. Transcription factors (TFs) are important regulators involved in the process of signal transduction and gene expression regulation under environmental stresses. Among them, WRKY is the most extensively studied TF family in plant stress responses. It is of great significance to explore its function and molecular mechanism for genetic improvement of plant stress tolerance. The WRKY family is a unique TF superfamily, which play important roles in many life processes. WRKY TFs function effectively in most abiotic stress responses or tolerances in various plants. In response to abiotic stresses, some WRKY TFs can be rapidly induced to promote signal transduction and regulate the expression of downstream stress responsive genes. In addition, WRKY TFs also play essential roles in regulating the response to salinity stress. Myrothamnus flabellifolia is native to southern Africa. It is highly aromatic and produces a robust profile of secondary compounds related to tolerance and defense, many of which have important applications. M. flabellifolia usually grows in environments with high abiotic stress (e.g. drought, high temperature, irradiation). Through a long-term evolution, M. flabellifolia develops strong survival strategies, including developed root systems and the ability to recover from dehydration to adapt to the extremely arid environments. However, due to the lack of genomic resources, genes of M. flabellifolia associated with stress tolerance and the underlying mechanisms are largely unknown. A recent transcriptome investigation of M. flabellifolia focusing on dynamic dehydration response showed that a variety of TFs may function in the transcriptional regulatory network during dehydration, among which MfWRKY41 was significantly upregulated at the initial stage of dehydration treatment, suggesting that it may be involved in the regulation of desiccation tolerance. To further validate this speculation, in this study, MfWRKY41 gene was cloned, and its role in enhancing drought tolerance and salinity tolerance was investigated. Comparing to wildtype, the four transgenic lines overexpressing MfWRKY41 showed better growth performance under drought and salt treatments, and exhibited higher chlorophyll content, lower water loss rate and stomatal aperture and better osmotic adjustment capacity. These results indicated that MfWRKY41 of M. flabellifolia positively regulates drought as well as salinity responses. Interestingly, the roots system of the transgenic lines was enhanced by MfWRKY41 under both normal and stressful conditions, and the antioxidation ability was also significantly improved under both stress treatments. Therefore, MfWRKY41 may have potential application values in genetic improvement of plant tolerance to drought and salinity stresses. The molecular mechanism involving in the regulatory roles of MfWRKY41 worthy being explored in the future.

Technical Abstract: Myrothamnus flabellifolia is the only woody resurrection plant discovered so far and could recover from extremely desiccation condition. However, few genes related to its strong drought tolerance have been characterized, and the underlying molecular mechanisms remains mysterious. Members of WRKY transcription factor family are effective in regulating abiotic stress responses or tolerance in various plants. An early dehydration-induced gene encoding transcription factor MfWRKY41 was isolated from M. flabellifolia, which is homologous to AtWRKY41 of Arabidopsis. It contains the typical WRKY domain and zinc finger motif, and is located in the nucleus. Comparing to wildtype, the four transgenic lines overexpressing MfWRKY41 showed better growth performance under drought and salt treatments, and exhibited higher chlorophyll content, lower water loss rate and stomatal aperture and better osmotic adjustment capacity. These results indicated that MfWRKY41 of M. flabellifolia positively regulates drought as well as salinity responses. Interestingly, the roots system of the transgenic lines was enhanced by MfWRKY41 under both normal and stressful conditions, and the antioxidation ability was also significantly improved under both stress treatments. Therefore, MfWRKY41 may have potential application values in genetic improvement of plant tolerance to drought and salinity stresses. The molecular mechanism involving in the regulatory roles of MfWRKY41 worthy being explored in the future.