Integrating transcriptome and metabolome to analyze the intrinsic mechanism of CaCl2 mitigation of H2O2 inhibition of pea primary root growth

Normal root growth is essential for plant uptake of soil nutrients and water, and abiotic stresses can inhibit root development. Previous studies have shown that exogenous H2O2 inhibits the geotropism of Pisum sativum primary roots, but the exact mechanism is unclear. In this study, CaCl2 was found to alleviate H2O2-induced weakening of Pisum sativum primary roots toward the ground. Through combined transcriptome and metabolome analysis, we found that a large number of DEGs and differential metabolites were enriched in the "Starch and sucrose metabolism (ko00500)" and "Flavonoid biosynthesis (ko00941)." The pathways in which DEGs were individually enriched were "response to oxidative stress(GO:0006979), Cellular Component: plant-type cell wall (GO:0009505), and Plant hormone signal transduction (ko04075)." A decrease in starch content, an increase in per-oxidase (EC 1.11.1.7) activity, a decrease in endogenous H2O2 content, and an accumulation of lignin content in the root system under H2O2 treatment were detected by determining the relevant indexes, and the imposition of CaCl2 led to the reversal of this phenomenon. In summary, the results of the present study indicate that the response of Pisum sativum primary roots to H2O2 and CaCl2 is mainly mediated by regulating the expression of genes that synthesize per-oxidase, starch, lignin, and flavonoid, thereby altering the accumulation of these metabolites in the root system. This provides new insights into the growth mechanisms of Pisum sativum primary roots under abiotic stress.