Scientia Agricultura Sinica ›› 2020, Vol. 53 ›› Issue (17): 3455-3466.doi: 10.3864/j.issn.0578-1752.2020.17.004

• CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS • Previous Articles     Next Articles

Isolation, Identification, and Response to Abiotic Stress of MsWRKY42 Gene from Medicago sativa L.

LIU JiaoJiao1(),WANG XueMin2,MA Lin2,CUI MiaoMiao2,CAO XiaoYu2,ZHAO Wei1()   

  1. 1College of Agriculture, Henan University of Science and Technology/College of Tree Peony, Luoyang 471023, Henan
    2Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193
  • Received:2019-10-30 Accepted:2020-02-16 Online:2020-09-01 Published:2020-09-11
  • Contact: Wei ZHAO E-mail:1192771534@qq.com;zhaowei1@haust.edu.cn

Abstract:

【Objective】The WRKY gene family in plants encodes a large group of transcription factors (TFs) that play essential roles in diverse stress responses, developmental and physiological processes. It laid a foundation for further research on the role of WRKY transcription factor in alfalfa stress-resistant molecular regulation by analyzing the role of MsWRKY42 transcription factor in alfalfa. 【Method】MsWRKY42 sequence was obtained by homologous alignment and sequence characteristics of it were analyzed by online bioinformatics tools. The phylogenetic tree of MsWRKY42 and Arabidopsis WRKY genes was constructed by MEGA-X. The putative cis-elements in promoter region of MsWRKY42 was analyzed by PlantCARE. The real-time quantitative PCR (qRT-PCR) was used to analyze the expression pattern of MsWRKY42 in different organs and its response to abiotic including NaCl (0.3 mol·L-1), PEG(15%), 4℃, 40℃, low phosphorus and ABA (0.1×10-3mol·L-1). The fusion expression vector of pCAMBIA1300- WRKY-GFP was constructed and delivered into Nicotiana benthamiana by Agrobacterium mediated method to determine the subcellular localization of WRKY protein. The yeast one-hybrid technique was used to analyze the binding activity of MsWRKY42 and the cis-acting element W-box.【Result】The gene contained a 1 692 bp open reading frame encoding 563 amino acids. Multiple sequence alignment and phylogenetic tree analysis results indicated that the protein is a member of the IIb sub-group WRKY family and contains a WRKY conserved domain and a C2H2 zinc finger motif. It has the highest similarity to AtWRKY42 in the Arabidopsis family, therefore, named as MsWRKY42. A variety of cis-acting elements were identified in the promoter region of MsWRKY42, including regulatory elements such as stress response, hormone response, and diurnal regulation. Real-Time PCR analysis showed that MsWRKY42 had the highest expression in roots and leaves. The expression of MsWRKY42 was up-regulated by NaCl, PEG, low temperature, high temperature, low phosphorus and ABA treatments. Subcellular localization indicated that MsWRKY42 was mainly located on the nucleus in plant cells. The results of the binding activity analysis showed that MsWRKY42 was able to specifically bind to W-box.【Conclusion】MsWRKY42 is a typical transcription factor, which can specifically bind to cis-acting elements, and the protein is localized in the nucleus. The gene was expressed in different tissues of alfalfa, and was induced by NaCl, PEG, high temperature, low phosphorus and ABA treatment. It is speculated that the MsWRKY42 gene may play a role in response to multiple stress defense responses as a WRKY transcription factor.

Key words: alfalfa, WRKY transcription factor, abiotic stress, subcellular localization, binding activity analysis

Table 1

Promoter prediction by PlantCARE"

顺式作用元件
Cis-elements
序列
Sequence (5′-3′)
功能
Function
数量
No.
CGTCA-motif CGTCA 参与MeJA反应的顺式作用调节元件
Cis-acting regulatory element involved in the MeJA-responsiveness
2
GARE-motif TCTGTTG 赤霉素反应元件
Gibberellin-responsive element
1
I-box GTATAAGGCC 部分光响应元件
Part of a light responsive element
1
Box 4 ATTAAT 参与光响应的保守 DNA 模块的部分元件
Part of a conserved DNA module involved in light responsiveness
5
HD-Zip 3 GTAAT(G/C)ATTAC 蛋白质结合位点
Protein binding site
1
circadian CAAAGATATC 参与昼夜节律顺行调控元件
Cis-acting regulatory element involved in circadian control
1
TCCC-motif TCTCCCT 部分光响应元件
Part of a light responsive element
1
TGACG-motif TGACG 参与MeJA反应的顺式作用调节元件
Cis-acting regulatory element involved in the MeJA-responsiveness
2
3-AF3 binding site CACTATCTAAC 保守DNA模块阵列的一部分(CMA3)
Part of a conserved DNA module array (CMA3)
1
TATC-box TATCCCA 参与赤霉素反应的顺式作用元件
Cis-acting element involved in gibberellin-responsiveness
1
Sp1 GGGCGG 光响应元件
Light responsive element
1
TC-rich repeats ATTCTCTAAC 参与防御和胁迫反应的顺式作用元件
Cis-acting element involved in defense and stress responsiveness
1
GCN4_motif TGAGTCA 参与胚乳表达的顺式调控元件
Cis-regulatory element involved in endosperm expression
1
CAAT-box CAAAT 启动子和增强子区域中常见的顺式作用元件
Common cis-acting element in promoter and enhancer regions
16
G-Box CACGTG 参与光响应顺式作用元件
Cis-acting regulatory element involved in light responsiveness
5
GATA-motif GATAGGG 部分光响应元件
Part of a light responsive element
1
O2-site GATGA(C/T)(A/G)TG(A/G) 参与玉米醇溶蛋白代谢调节的顺式作用调节元件
Cis-acting regulatory element involved in zein metabolism regulation
1
GT1-motif GGTTAAT 光响应元件
Light responsive element
2
TATA-box TATA 在转录起始的-30 附近的核心启动子元件
Core promoter element around -30 of transcription start
41
ARE AAACCA 厌氧诱导必需元件
Cis-acting regulatory element essential for the anaerobic induction
2
GC-motif CCCCCG 参与缺氧特异性诱导的类似增强子元件
Enhancer-like element involved in anoxic specific inducibility
1
TCA-element CCATCTTTTT 参与水杨酸响应的顺式作用元件
Cis-acting element involved in salicylic acid responsiveness
1
TCT-motif TCTTAC 部分光响应元件
Part of a light responsive element
2
ATCT-motif AATCTAATCC 部分参与光响应的保守DNA区域
Part of a conserved DNA module involved in light responsiveness
2
ABRE CACGTG 参与脱落酸反应的顺式作用元件
Cis-acting element involved in the abscisic acid responsiveness
5

Fig. 1

PCR amplified product of MsWRKY42 M: Trans2K Plus II Marker; 1: PCR amplified product"

Fig. 2

Amino acid sequence alignment of MsWRKY42 with other homologous proteins"

Fig. 3

A phylogenetic tree constructed based on WRKYs of Arabidopsis thaliana and MsWRKY42"

Fig. 4

Prediction of second structure of MsWRKY42 The red line represents the extension chain; The purple line represents the random coil; The blue line represents the alphahelix"

Fig. 5

Prediction of the tertiary structure of MsWRKY42"

Fig. 6

Subcellular localization of MsWRKY42 in lower epidermal cells of Nicotiana benthamiana The images are taken by green fluorescence, visible light, merged green fluorescence and visible light. 35S::GFP: The Agrobacterium tumefaciens strain carrying the empty vector pCAMBIA1300-GFP. 35S::MsWRKY42::GFP: The A. tumefaciens strain carrying the recombinant vector pCAMBIA1300- MsWRKY42-GFP. Scale bar = 25 μm"

Fig. 7

Expression pattern of MsWRKY42 in different tissues of alfalfa Different letters indicate statistical difference (P<0.05). The same as below"

Fig. 8

The expression of MsWRKY42 gene under different stress"

Fig. 9

Binding activity analysis of MsWRKY42 protein A: 3-AT concentration screening; B: Growth state of four yeast transformants diluted in different times on SD/-His-Leu-ura medium"

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