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BackgroundSoil salinization is one of the major environmental constraints to plant growth and agricultural production worldwide. Signaling components involving calcium (Ca2+) and the downstream calcium-dependent protein kinases (CPKs) play key roles in the perception and transduction of stress signals. However, the study of CPKs in cotton and their functions in response to salt stress remain unexplored.ResultsA total of 98 predicted CPKs were identified from upland cotton (Gossypium hirsutum L. ‘TM-1’), and phylogenetic analyses classified them into four groups. Gene family distribution studies have revealed the substantial impacts of the genome duplication events to the total number of GhCPKs. Transcriptome analyses showed a wide distribution of CPKs’ expression among different organs. A total of 19 CPKs were selected for their rapid responses to salt stress at the transcriptional level, most of which were also incduced by the thylene-releasing chemical ethephon, suggesting a partal overlap of the salinity and ethylene responses. Silencing of 4 of the 19 CPKs (GhCPK8, GhCPK38, GhCPK54, and GhCPK55) severely compromised the basal cotton resistance to salt stress.ConclusionsOur genome-wide expression analysis of CPK genes from up-land cotton suggests that CPKs are involved in multiple developmental responses as well as the response to different abiotic stresses. A cluster of the cotton CPKs was shown to participate in the early signaling events in cotton responses to salt stress. Our results provide significant insights on functional analysis of CPKs in cotton, especially in the context of cotton adaptions to salt stress.Electronic supplementary materialThe online version of this article (doi: 10.1186/s12870-018-1230-8) contains supplementary material, which is available to authorized users.

As the global water shortage becomes increasingly serious, it is highly imperative to develop efficient, renewable, and large-scale water purification devices. Herein, an efficient solar-driven water purification device of wood coated with Fe2O3 nanoparticle-decorated carbon nanotubes (Fe2O3/CNT) is fabricated in only a few seconds by one-step combustion of ferric acetylacetonate in an ambient environment. The thin layer of the Fe2O3/CNT hybrid coated on the upper surface of the wood serves as a solar-light absorber for converting solar energy to thermal energy, while the thermally insulating wood layer with vertically aligned channels endows the device with rapid water upward transport and localizes the generated heat inside the Fe2O3/CNT layer for solar-driven water evaporation. As a result, the wood/Fe2O3/CNT device achieves a high water steam generation capability of 1.42 kg m–2 h–1 along with an excellent evaporation efficiency of 87.2% under 1 sun irradiation, higher than most of the wood-based solar-driven water evaporation device reported. This device is also efficient in the purification of seawaters and wastewaters. This work demonstrates a rapid and facile methodology for large-scale fabrication of wood/Fe2O3/CNT devices for efficient solar-driven water purification.