BackgroundIn plants, calcium-dependent protein kinases (CDPKs) are involved in tolerance to abiotic stresses and in plant seed development. However, the functions of only a few rice CDPKs have been clarified. At present, it is unclear whether CDPKs also play a role in regulating spikelet fertility.ResultsWe cloned and characterized the rice CDPK gene, OsCPK9. OsCPK9 transcription was induced by abscisic acid (ABA), PEG6000, and NaCl treatments. The results of OsCPK9 overexpression (OsCPK9-OX) and OsCPK9 RNA interference (OsCPK9-RNAi) analyses revealed that OsCPK9 plays a positive role in drought stress tolerance and spikelet fertility. Physiological analyses revealed that OsCPK9 improves drought stress tolerance by enhancing stomatal closure and by improving the osmotic adjustment ability of the plant. It also improves pollen viability, thereby increasing spikelet fertility. In OsCPK9-OX plants, shoot and root elongation showed enhanced sensitivity to ABA, compared with that of wild-type. Overexpression and RNA interference of OsCPK9 affected the transcript levels of ABA- and stress-responsive genes.ConclusionsOur results demonstrated that OsCPK9 is a positive regulator of abiotic stress tolerance, spikelet fertility, and ABA sensitivity.
BackgroundCalcineurin B-like (CBL) proteins belong to a unique group of calcium sensors in plant that decode the Ca2+ signature by interacting with CBL-interacting protein kinases (CIPKs). Although CBL-CIPK complexes have been shown to play important roles in the responses to various stresses in plants, little is known about their functions in wheat.ResultsA total of seven TaCBL and 20 TaCIPK genes were amplified from bread wheat, Triticum aestivum cv. Chinese Spring. Reverse-transcriptase-polymerase chain reaction (RT-PCR) and in silico expression analyses showed that TaCBL and TaCIPK genes were expressed at different levels in different tissues, or maintained at nearly constant expression levels during the whole life cycle of the wheat plant. Some TaCBL and TaCIPK genes showed up- or down-regulated expressions during seed germination. Preferential interactions between TaCBLs and TaCIPKs were observed in yeast two-hybrid and bimolecular fluorescence complementation experiments. Analyses of a deletion series of TaCIPK proteins with amino acid variations at the C-terminus provided new insights into the specificity of the interactions between TaCIPKs and TaCBLs, and indicated that the TaCBL–TaCIPK signaling pathway is very complex in wheat because of its hexaploid genome. The expressions of many TaCBLs and TaCIPKs were responsive to abiotic stresses (salt, cold, and simulated drought) and abscisic acid treatment. Transgenic Arabidopsis plants overexpressing TaCIPK24 exhibited improved salt tolerance through increased Na+ efflux and an enhanced reactive oxygen species scavenging capacity.ConclusionsThese results contribute to our understanding of the functions of CBL-CIPK complexes and provide the basis for selecting appropriate genes for in-depth functional studies of CBL–CIPK in wheat.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-015-0657-4) contains supplementary material, which is available to authorized users.
Calcineurin B-like protein-interacting protein kinases (CIPKs) have been found to be responsive to abiotic stress. However, their precise functions and the related molecular mechanisms in abiotic stress tolerance are not completely understood, especially in wheat. In the present study, TaCIPK29 was identified as a new member of CIPK gene family in wheat. TaCIPK29 transcript increased after NaCl, cold, methyl viologen (MV), abscisic acid (ABA) and ethylene treatments. Over-expression of TaCIPK29 in tobacco resulted in increased salt tolerance, which was demonstrated by higher germination rates, longer root lengths and better growth status of transgenic tobacco plants compared to controls when both were treated with salt stress. Physiological measurements indicated that transgenic tobacco seedlings retained high K+/Na+ ratios and Ca2+ content by up-regulating some transporter genes expression and also possessed lower H2O2 levels and reduced membrane injury by increasing the expression and activities of catalase (CAT) and peroxidase (POD) under salt stress. Moreover, transgenic lines conferred tolerance to oxidative stress by increasing the activity and expression of CAT. Finally, TaCIPK29 was located throughout cells and it preferentially interacted with TaCBL2, TaCBL3, NtCBL2, NtCBL3 and NtCAT1. Taken together, our results showed that TaCIPK29 functions as a positive factor under salt stress and is involved in regulating cations and reactive oxygen species (ROS) homeostasis.
Aquaporin proteins (AQPs) have been shown to be involved in abiotic stress responses. However, the precise role of AQPs, especially in response to cold stress, is not understood in wheat (Triticum aestivum). In the present study, quantitative real time polymerase chain reaction (qRT-PCR) analysis revealed that TaAQP7 expression increased in leaves, but decreased in roots after cold treatment. Expression of TaAQP7 in tobacco plants resulted in increased root elongation and better growth compared with wild-type (WT) plants under cold stress. Moreover, after cold treatment, the transgenic tobacco lines exhibited higher chlorophyll contents, lower levels of malondialdehyde (MDA), and less ion leakage (IL) than WT plants. Thus, expression of TaAQP7 enhanced cold stress tolerance in transgenic tobacco. Taken together, our results suggest that TaAQP7 confers cold stress tolerance by relieving membrane damage in the transgenic plants.
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