Abstract
Organic molecules of biochar’s leacheates are known to increase the cold resistance of rice seedlings. Yet, it remains unclear whether the organic molecules of biochar leacheates can interact with the abscisic acid (ABA) signaling pathway associated with low temperature. This study used experiments and bioinformatics (molecular docking) to determine which of the organic molecules of biochar’s leacheates could influence the ABA signaling pathway. Specifically, we investigated whether these molecules affected ABA, a plant hormone linked to cold resistance. The contents of endogenous ABA and its precursor carotenoids were determined under low-temperature stress (10°C) and treatment with different concentrations of biochar leacheates. With increased leacheate concentrations, the endogenous ABA and carotenoid contents also increased, as did the expression of ABA- and cold-related genes. When rice seedlings were instead treated with exogenous ABA, it also affected the above-measured indexes; hence, we surmised that certain water-soluble organic molecules of biochar could exert a similar effect as ABA. We first used gas chromatography/mass spectrometry (GC/MS) to identify the organic molecules in the biochar extract, and then we used molecular docking software Autodock to show how they interact. We found that the molecule (1R, 2R, 4S)-2-(6-chloropyridin-3-yl)-7-azabicyclo(2.2.1)heptane was simplified, as Cyah could dock with the ABA receptor protein OsPYL2 in rice, which shows Cyah in biochar is probably an analog of ABA, with a similar function. Based on these results, we conclude that organic molecules of biochar’s leacheates could enter into rice plants and interact with ABA-related proteins to affect the ABA signaling pathway, thereby improving the cold stress resistance of plants.
Highlights
Biochar is the product of heating biomass in the absence of or with limited air to above 250◦C in a process called charring or pyrolysis (Lehmann and Joseph, 2015)
We identified those proteins involved in abscisic acid (ABA) pathways as influenced by biochar organic molecules via comparison with the National Center for Biotechnology Information (NCBI) database and utilized the Research Collaboratory for Structural Bioinformatics (RCSB) protein database to obtain their structures
Rice plants treated with different concentrations of biochar leacheates were grown in the same pots under well-watered conditions, and all of them developed the same phenotype after 5 days of growth at 28◦C
Summary
Biochar is the product of heating biomass in the absence of or with limited air to above 250◦C in a process called charring or pyrolysis (Lehmann and Joseph, 2015). Biochar Affect Abscisic Acid Pathway and promoted the nutritional quality of grass (Rafiq et al, 2017); and biochar alone or in a co-application stimulated growth in halophyte plants, including their germination, root development, and biomass (Zheng et al, 2018). Biochar can affect plant growth via several plausible mechanisms: (1) by improving soil and regulating the soil microbial environment, which indirectly or directly affects plant root growth and affects the whole plant (Lehmann and Joseph, 2015; Zheng et al, 2018); (2) by providing nutrients for plants to uptake (Wang et al, 2018); (3) by organic molecules on the surface of biochar that can promote or inhibit plant growth (Graber et al, 2010; Lievens et al, 2014; Gale et al, 2016; Yuan et al, 2017); and (4) by affecting endogenous plant hormones, which can impact plant development and physiology (Yang et al, 2015; French and Iyerpascuzzi, 2018; Waqas et al, 2018). The previous paper dealt with low temperature (cold), yet the relationship between biochar and abscisic acid (ABA)—which is closely related to low temperature—has not been reported on
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