Kiranmai K, Lokanadha Rao G, Pandurangaiah M, Nareshkumar A, Amaranatha Reddy V, Lokesh U, Venkatesh B, Anthony Johnson AM, Sudhakar C.

Front Plant Sci. 2018 Mar 16;9:346. doi: 10.3389/fpls.2018.00346.

Abstract

Drought stress has adverse effects on growth, water relations, photosynthesis and yield of groundnut. WRKY transcription factors (TFs) are the plant-specific TFs which regulate several down-stream stress-responsive genes and play an essential role in plant biotic and abiotic stress responses. We found that WRKY3 gene is highly up-regulated under drought stress conditions and therefore isolated a new WRKY3TF gene from a drought-adapted horsegram (Macrotyloma uniflorum Lam. Verdc.). Conserved domain studies revealed that protein encoded by this gene contains highly conserved regions of two WRKY domains and two C2H2 zinc-finger motifs. The fusion protein localization studies of transient MuWRKY3-YFP revealed its nuclear localization. Overexpression of MuWRKY3 TF gene in groundnut(Arachis hypogaea L.) showed increased tolerance to drought stress compared to wild-type (WT) plants. MuWRKY3 groundnut transgenics displayed lesser and delayed wilting symptoms than WT plants after 10-days of drought stress imposition. The transgenic groundnut plants expressing MuWRKY3 showed less accumulation of malondialdehyde, hydrogen peroxide (H₂O₂), and superoxide anion (O₂^∙-), accompanied by more free proline, total soluble sugar content, and activities of antioxidant enzymes than WT plants under drought stress. Moreover, a series of stress-related LEA, HSP, MIPS, APX, SOD, and CAT genes found up-regulated in the transgenic groundnut plants. The study demonstrates that nuclear-localized MuWRKY3 TF regulates the expression of stress-responsive genes and the activity of ROS scavenging enzymes which results in improved drought tolerance in groundnut. We conclude that MuWRKY3 may serve as a new putative candidate gene for the improvement of stress resistance in plants.

See: https://www.ncbi.nlm.nih.gov/pubmed/29616059

Figure 3: (A) A linear map of MuWRKY3 overexpressing vector with GUS and NptII marker genes for screening, 35S promoter and polyA terminator. Entire expression cassette is flanked by left and right borders in pCAMBIA2301. (B) Screening of transgenic and WT plants on half strength MS medium containing 200 mg/lit kanamycin and their acclimatization. (C) GUS histochemical staining of WT and transgenic seedlings at T₃ generation. (D) PCR Amplification of MuWRKY3 gene GUS and NptII gene from genomic DNA of transgenic and WT plants: M, gene ruler mix; WT, wild-type; TR1 to TR10, transgenic lines.