Heterologous expression of MfWRKY7 of resurrection plant Myrothamnus flabellifolia enhances salt and drought tolerance in Arabidopsis

Authors: HUANG, ZHUO - Sichuan Agricultural University; LIU, LING - Sichuan Agricultural University; JIAN, LIN-LI - Sichuan Agricultural University; XU, WENXIN - Sichuan Agricultural University; WANG, JIATONG - Sichuan Agricultural University; LI, YAXUAN - Sichuan Agricultural University; Jiang, Cai-Zhong

Submitted to: International Journal of Molecular Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/13/2022
Publication Date: 7/17/2022
Citation: Huang, Z., Liu, L., Jian, L., Xu, W., Wang, J., Li, Y., Jiang, C. 2022. Heterologous expression of MfWRKY7 of resurrection plant Myrothamnus flabellifolia enhances salt and drought tolerance in Arabidopsis. International Journal of Molecular Sciences. 23(14). Article 7890. https://doi.org/10.3390/ijms23147890.
DOI: https://doi.org/10.3390/ijms23147890

Interpretive Summary: Abiotic stresses such as drought, salinity and low temperature are the main environmental factors negatively affecting plant growth and development. Under long-term natural selection, plants have evolved extremely complex mechanisms to adopt to adverse environments through generating morphological, physiological and gene expression adaptive regulatory responses. Transcription factors (TFs) are among the most important regulators in this process. Many TFs families, such as WRKY, AP2/ERF and NAC, have been reported to play important and unique roles in responses to abiotic stress. WRKY TFs belong to a plant-specific transcription factor family. In recent years, increasing evidences indicated that WRKYs are involved in various abiotic stress responses in plants, especially in responses to salt and drought stresses and are considered as the reservoir of regulators for abiotic stress responses and needs further investigation. The resurrection plant Myrothamnus flabellifolia, which believed to be one of the most ancient plants on the planet, is widely used as African traditional medicine. They are distributed throughout southern Africa in disjunct populations from Namibia to Tanzania, with the highest density of plants occurring in South Africa and Zimbabwe. It was known in isiZulu as Uvukakwabafile, which means ‘awake from the dead’. This might originate from its adaptability to extreme drought surroundings, which benefits from evolved powerful survival strategies including a well-developed root system and the capability to recover from dehydration. However, few genes related to drought tolerance of M. flabellifolia were characterized and the underlying molecular mechanism is largely unknown. A previous study showed that many different transcription factors are involved in dehydration responses of M. flabellifolia by transcriptome sequencing, in which MfWRKY7 is immediately up-regulated in the early stage of dehydration, but its roles in stress responses are unclear. In this study, we cloned MfWRKY7 and overexpressed it in Arabidopsis. Overexpression of MfWRKY7 in Arabidopsis increased root length and tolerance to drought and NaCl at both seedling and adult stages. Further investigation indicated that MfWRKY7 transgenic plants had higher contents of chlorophyll, proline, soluble protein, and soluble sugar, but lower water loss rate, malondialdehyde content compared with wild type plants under two stresses. Moreover, the higher activities of antioxidant enzymes and lower accumulation of O2- and H2O2 in MfWRKY7 transgenic plants were also found, indicating enhanced antioxidation capacity by MfWRKY7. These findings showed that MfWRKY7 may function in positive regulation of responses to drought and salinity stresses, and therefore has potential application value in genetic improvement of plant tolerance to abiotic stress.

Technical Abstract: Drought and salinity have become major environment problems that affect the production of agriculture, forestry and horticulture. Identification of stress tolerance genes from plants adaptive to harsh environments might be a feasible strategy for plant genetic improvement to address the challenges brought by global climate change. In this study, a dehydration-induced gene MfWRKY7 of resurrection Plant Myrothamnus Flabellifolia, encoding a group IId WRKY transcription factor, was cloned and characterized. Overexpression of MfWRKY7 in Arabidopsis increased root length and tolerance to drought and NaCl at both seedling and adult stages. Further investigation indicated that MfWRKY7 transgenic plants had higher contents of chlorophyll, proline, soluble protein, and soluble sugar, but lower water loss rate, malondialdehyde content compared with wild type plants under two stresses. Moreover, the higher activities of antioxidant enzymes and lower accumulation of O2- and H2O2 in MfWRKY7 transgenic plants were also found, indicating enhanced antioxidation capacity by MfWRKY7. These findings showed that MfWRKY7 may function in positive regulation of responses to drought and salinity stresses, and therefore has potential application value in genetic improvement of plant tolerance to abiotic stress.