New insights into the role of cyanide in the promotion of seed germination in tomato.

BACKGROUND: Cyanide is a natural metabolite that exists widely in plants, and it is speculated to be involved in the regulation of various growth and development processes of plants in addition to being regarded as toxic waste. Previous studies have shown that exogenous cyanide treatment helps to improve seed germination, but the mechanism is still unclear. In this study, tomato (Solanum lycopersicum cv. Alisa Craig) was used as the material, and the effects of cyanide pretreatment at different concentrations on tomato seed germination were investigated. RESULTS: The results showed that exogenous application of a lower concentration of cyanide (10 µmol/L KCN) for 12 h strongly increased the tomato seed germination rate. RNA-Seq showed that compared with the control, a total of 15,418 differentially expressed genes (P<0.05) were obtained after pretreatment with KCN for 12 h, and in the next 12 h, a total of 13,425 differentially expressed genes (P<0.05) were regulated. GO and KEGG analyses demonstrated that exogenous KCN pretreatment was involved in regulating the expression (mainly downregulation) of seed storage proteins, thereby accelerating the degradation of stored proteins for seed germination. In addition, KCN pretreatment was also involved in stimulating glycolysis, the TCA cycle and oxidative phosphorylation. Notably, it is shown that KCN acted on the regulation of plant hormone biosynthesis and perception, i.e., down-regulated the gene expression of ABA biosynthesis and signal transduction, but up-regulated the expression of genes related to GA biosynthesis and response. Consistent with this, plant hormone measurements confirmed that the levels of ABA were reduced, but GA levels were induced after pretreatment with KCN. CONCLUSION: These findings provide new insights into the regulation of seed germination by cyanide, that is cyanide-mediated seed germination occurs in a time- and dose-dependent manner, and is related to the mobilization of energy metabolism and the regulation of some plant hormone signals.

Overexpressed ß-cyanoalanine synthase functions with alternative oxidase to improve tobacco resistance to salt stress by alleviating oxidative damage.

ß-Cyanoalanine synthase (ß-CAS) is an enzyme involved in cyanide detoxification. However, little information is available regarding the effects of ß-CAS activity changes on plant resistance to environmental stress. Here, we found that ß-CAS overexpression (CAS-OE) improves the resistance of tobacco plants to salt stress, whereas plants with ß-CAS silencing suffer more oxidative damage than wild-type plants. Notably, blocking respiration by the alternative oxidase (AOX) pathway significantly aggravates stress injury and impairs the salt stress tolerance mediated by CAS-OE. These findings present novel insights into the synergistic effect between ß-CAS and AOX in protecting plants from salt stress, where ß-CAS plays a vital role in restraining cyanide accumulation, and AOX helps to alleviate the toxic effect of cyanide.