Abstract
Phelipanche aegyptiaca is one of the most devastating agricultural weed pests and poses a serious threat to crop production. However, few studies have addressed the potential of silicon nanoparticles (SiNPs) to ameliorate the challenge of Phelipanche infection, and the exact mechanisms underlying SiNPs-induced stress tolerance are still largely unknown. Therefore, our study was conducted to investigate the ramifications on the primary and secondary metabolism of pea (Pisum sativum) treated with SiNPs under the menace of Phelipanche infection. In general, Phelipanche infection reduced photosynthesis, which altered the carbon and nitrogen metabolism including primary metabolism, which is mandatory for maintaining pea growth. In addition to a reduction in growth, Phelipanche infection also induced membrane damage, i.e., high lipid peroxidation. In contrast, a pre-treatment with SiNPs increased the accumulation of Si in the pea root and shoot, which not only diminished the infection rate but also significantly alleviated the deleterious effect of Phelipanche infection. SiNPs improved photosynthesis, which in turn increased the sugar metabolism (e.g., invertase, sucrose synthase, starch synthase and amylase). Consequently, there was an increase in sugar consumption by the dark respiration processes, which stimulated the accumulation of organic acids. This also provided a route for the biosynthesis of amino acids and fatty acids. For instance, we found an increase in phenylalanine content, which induced lignin accumulation in the pea root, which serves as a physical barrier against Phelipanche haustoria penetration. Moreover, there was an increase in osmoprotectants (e.g., proline and sucrose) and antioxidants (e.g., tocopherols), which reduced the sink strength of the parasite. Additionally, they maintained the cellular structure by reducing membrane lipid peroxidation. This was also supported by the observed decrease in photorespiration, which induced ROS production, as indicted by the low gly/ser ratio. Overall, this study demonstrates the potentiality of SiNPs in harnessing carbon and nitrogen metabolism differentially in pea organs to cope with the virulence of Phelipanche infection.