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Cogon grass (Imperata cylindrica (L.) Beauv. var. major (Nees) Hubb.) is one of the top-ten weeds worldwide. It is also a C4 medicinal plant. In particular, an ecotype from Chuwei (CW) mangrove forest was found to be salt tolerant. Comparative proteomic analysis using two-dimensional (2D)-difference in gel electrophoresis coupled with liquid chromatography-mass spectrometry (LC-MS) was carried out to identify responsive leaf proteins in the CW ecotype and salt-intolerant Sarlun (SL) population following three days of 150 mM sodium chloride salt stress treatment. We identified five photosynthesis proteins including Rubisco small subunit, uncharacterized protein LOC100194054, Cyt b6-f, oxygen-evolving enhancer 2, and photosystem I reaction center subunit IV which were significantly up- or down-regulated by salt stress in CW ecotype but not SL population. Gene ontology enrichment analysis showed that photosynthesis was over-represented. The mass spectrometry proteomics data were deposited to the ProteomeXchange Consortium via the PRIDE partner repository with the dataset identifier PXD008482. Taken together, our proteomic study identified differentially accumulated proteins which provide additional evidence of ecophysiological variation in two natural variants of I. cylindrica.

Background Basic region/leucine zippers (bZIPs) are transcription factors (TFs) encoded by a large gene family in plants. ABF3 and ABI5 are Group A bZIP TFs that are known to be important in abscisic acid (ABA) signaling. However, questions of whether ABF3 regulates ABI5 are still present. Results In vitro kinase assay results showed that Thr-128, Ser-134, and Thr-451 of ABF3 are calcium-dependent protein kinase phosphorylation sites. Bimolecular fluorescence complementation (BiFC) analysis results showed a physical interaction between ABF3 and 14-3-3ω. A Thr-451 to Ala point mutation abolished the interaction but did not change the subcellular localization. In addition, the Arabidopsis protoplast transactivation assay using a luciferase reporter exhibited ABI5 activation by either ABF3 alone or by co-expression of ABF3 and 14-3-3ω. Moreover, chromatin immunoprecipitation-qPCR results showed that in Arabidopsis, ABI5 ABA-responsive element binding proteins (ABREs) of the promoter region (between − 1376 and − 455) were enriched by ABF3 binding under normal and 150 mM NaCl salt stress conditions. Conclusion Taken together, our results demonstrated that ABI5 expression is regulated by ABF3, which could contribute to salt stress tolerance in Arabidopsis thaliana. Electronic supplementary material The online version of this article (10.1186/s40529-019-0264-z) contains supplementary material, which is available to authorized users.

Additional file 4. The predicted ABRE cis-elements in the ABI5 promoter sequence (− 1 to − 2055).

Ethylene is an important plant hormone that regulates developmental processes in plants. The ethylene biosynthesis pathway is a highly regulated process at both the transcriptional and post-translational level. The transcriptional regulation of these ethylene biosynthesis genes is well known. However, post-translational modifications of the key ethylene biosynthesis enzyme 1-aminocyclopropane-1-carboxylate (ACC) synthase (ACS) are little understood. In vitro kinase assays were conducted on the type III ACS, AtACS7, fusion protein and peptides to determine whether the AtACS7 protein can be phosphorylated by calcium-dependent protein kinase (CDPK). AtACS7 was phosphorylated at Ser216, Thr296, and Ser299 by AtCDPK16 in vitro. To investigate further the function of the ACS7 gene in Arabidopsis, an acs7-1 loss-of-function mutant was isolated. The acs7-1 mutant exhibited less sensitivity to the inhibition of root gravitropism by treatment with the calcium chelator ethylene glycol tetraacetic acid (EGTA). Seedlings were treated with gradient concentrations of ACC. The results showed that a certain concentration of ethylene enhanced the gravity response. Moreover, the acs7-1 mutant was less sensitive to inhibition of the gravity response by treatment with the auxin polar transport inhibitor 1-naphthylphthalamic acid, but exogenous ACC application recovered root gravitropism. Altogether, the results indicate that AtACS7 is involved in root gravitropism in a calcium-dependent manner in Arabidopsis.