Functional Characterization on Wheat Protein Kinase Gene <i>TaSnRK2.1</i> in Mediating Plant Resistance to Drought Stress

Abstract

The protein kinase type of sucrose non-fermenting-1 related protein kinase 2 (SnRK2) plays an important role in regulating plant growth and development and in mediating plant resistance to abiotic stresses given that it involves transduction of distinct internal and abiotic stress signaling. In this study, <i>TaSnRK2.1</i>, a gene of SnRK2 family in wheat, was investigated focusing on its molecular characterization, expression pattern upon drought stress, and the biological function in mediating plant drought tolerance. At nucleic acid level, <i>TaSnRK2.1</i> is highly homologous to its counterparts of SnRK2 kinase family genes in species of Polish wheat and barley, whose translated protein harbors a conserved catalytic domain of Ser/Thr kinase domain (aa 62-aa 318). Under a 48 h-regime drought treatment, the transcripts of <i>TaSnRK2.1</i> showed obvious response in roots and leaves, with the highest expression level reached at 24 h after treatment and maintaining a high level to 48 h under drought condition. Meanwhile, the transcripts of <i>TaSnRK2.1</i> in both roots and leaves induced by drought were recovered following the normal recovery treatment. Gene transgene analysis indicated that compared with wild type control (WT), the tobacco line with sense-overexpression of <i>TaSnRK2.1</i> (Sen 1) enlarged plant growth phenotypes, increased dry weights, promoted stomata closing, increased contents of cellular osmtic-regulatory substances including proline, soluble protein, and soluble sugar, enhanced photosynthetic capacity and elevated cellular protective enzyme activities under drought treatment. In contrast, the line with antisense-expression of <i>TaSnRK2.1</i> (Anti 1) reduced plant growth phenotypes, decreased biomass, slowed stomata closing, decreased the contents of cellular osmtic-regulatory substances, photosynthetic capacity and protective enzyme activities compared with WT plants treated by drought stress. Our investigation suggested that <i>TaSnRK2.1</i> is sensitive in response to drought signaling at transcriptional level that confers enhanced plant drought resistance by regulating physiological processes associated with stomata movement, cellular osmotic-regulatory substance metabolism, photosynthetsis, and protective enzyme activities.