Abstract
The WRKY transcription factors (TFs) are one of the largest families of TFs in plants and play multiple roles in plant development and stress response. In the present study, GmWRKY16 encoding a WRKY transcription factor in soybean was functionally characterized in Arabidopsis. GmWRKY16 is a nuclear protein that contains a highly conserved WRKY domain and a C2H2 zinc-finger structure, and has the characteristics of transcriptional activation ability, presenting a constitutive expression pattern with relative expression levels of over fourfold in the old leaves, flowers, seeds and roots of soybean. The results of quantitative real time polymerase chain reaction (qRT-PCR) showed that GmWRKY16 could be induced by salt, alkali, ABA, drought and PEG-6000. As compared with the control, overexpression of GmWRKY16 in Arabidopsis increased the seed germination rate and root growth of seedlings in transgenic lines under higher concentrations of mannitol, NaCl and ABA. In the meantime, GmWRKY16 transgenic lines showed over 75% survival rate after rehydration and enhanced Arabidopsis tolerance to salt and drought with higher proline and lower MDA accumulation, less water loss of the detached leaves, and accumulated more endogenous ABA than the control under stress conditions. Further studies showed that AtWRKY8, KIN1, and RD29A were induced in GmWRKY16 transgenic plants under NaCl treatment. The expressions of the ABA biosynthesis gene (NCED3), signaling genes (ABI1, ABI2, ABI4, and ABI5), responsive genes (RD29A, COR15A, COR15B, and RD22) and stress-related marker genes (KIN1, LEA14, LEA76, and CER3) were regulated in transgenic lines under drought stress. In summary, these results suggest that GmWRKY16 as a WRKY TF may promote tolerance to drought and salt stresses through an ABA-mediated pathway.
Highlights
The growth and yield of plants are seriously affected and inhibited by various biotic and abiotic stresses such as high salinity, drought and extreme temperatures, which are the main limiting factors (Hennig, 2012; Liang et al, 2017; He et al, 2018)
Based on recent reports on the functions of WRKY transcription factors (TFs) in soybean (Yu Y. et al, 2016), a salt and/or drought stress-induced gene encoding a transcription factor of WRKY proteins was obtained from the database under gene locus LOC100790175 and protein accession number of XP_003518509
The National Center for Biotechnology Information (NCBI) BLAST analysis of the full amino acids sequence indicated that the GmWRKY16 protein had a WRKY DNAbinding domain at the location of the peptide chain between 190 AA and 250 AA
Summary
The growth and yield of plants are seriously affected and inhibited by various biotic and abiotic stresses such as high salinity, drought and extreme temperatures, which are the main limiting factors (Hennig, 2012; Liang et al, 2017; He et al, 2018). The TFs from the bZIP, NAC, AP2, WRKY, PHD, DREB, or MYB families are essential for plant stress response by binding specific cis-acting elements to form a complex regulatory network. Overexpression of these TF genes usually increases the adaptability of plants to drought and salt stresses (Liu et al, 2012; Ying et al, 2012; Zong et al, 2016; Ullah et al, 2018)
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