Abstract
Drought, salinity and low temperatures are major factors limiting crop productivity and quality. Sucrose non-fermenting1-related protein kinase 2 (SnRK2) plays a key role in abiotic stress signaling in plants. In this study, TaSnRK2.8, a SnRK2 member in wheat, was cloned and its functions under multi-stress conditions were characterized. Subcellular localization showed the presence of TaSnRK2.8 in the cell membrane, cytoplasm and nucleus. Expression pattern analyses in wheat revealed that TaSnRK2.8 was involved in response to PEG, NaCl and cold stresses, and possibly participates in ABA-dependent signal transduction pathways. To investigate its role under various environmental stresses, TaSnRK2.8 was transferred to Arabidopsis under control of the CaMV-35S promoter. Overexpression of TaSnRK2.8 resulted in enhanced tolerance to drought, salt and cold stresses, further confirmed by longer primary roots and various physiological characteristics, including higher relative water content, strengthened cell membrane stability, significantly lower osmotic potential, more chlorophyll content, and enhanced PSII activity. Meanwhile, TaSnRK2.8 plants had significantly lower total soluble sugar levels under normal growing conditions, suggesting that TaSnRK2.8 might be involved in carbohydrate metabolism. Moreover, the transcript levels of ABA biosynthesis (ABA1, ABA2), ABA signaling (ABI3, ABI4, ABI5), stress-responsive genes, including two ABA-dependent genes (RD20A, RD29B) and three ABA-independent genes (CBF1, CBF2, CBF3), were generally higher in TaSnRK2.8 plants than in WT/GFP controls under normal/stress conditions. Our results suggest that TaSnRK2.8 may act as a regulatory factor involved in a multiple stress response pathways.
Highlights
Plant growth and crop production are adversely affected by environmental stresses such as extreme temperatures, drought, and high salinity
Scansite analysis indicated that TaSnRK2.8 has potential serine/threonine protein kinase activities, and like other Sucrose non-fermenting1related protein kinase 2 (SnRK2) family members, TaSnRK2.8 showed a two domain structure, characterized by an N-terminus catalytic domain close to the sucrose non-fermenting1 (SNF1)/AMP kinase region and a regulatory C-terminus region in which a stretch of acidic amino acids forms a negatively charged domain
A dehydration-inducible cDNA library of wheat was screened for transcripts that might be significantly upregulated under PEG stress
Summary
Plant growth and crop production are adversely affected by environmental stresses such as extreme temperatures, drought, and high salinity. Many studies have indicated the involvement of stress signaling cascades composed of second messengers [3], phospholipids [4], phosphatases [5] and protein kinases [6]. One of the major pathways by which extracellular stimuli are transduced into intracellular responses is the calcium-dependent protein kinase (CDPK) signaling cascade, which is activated by ABA and other diverse stress signals [7,8]. All these kinases are involved in regulation of carbon metabolism and energy status in their respective systems, whereas in plants, they may represent interfaces between metabolic and stress signaling. Accumulating evidence indicates that plant SnRKs may be hubs within a network of interacting signaling pathways, rather than being components of simple signaling cascades [10,11]
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