The Garlic Allelochemical Diallyl Disulfide Affects Tomato Root Growth by Influencing Cell Division, Phytohormone Balance and Expansin Gene Expression

Abstract

Diallyl disulfide (DADS) is a volatile organosulfur compound derived from garlic (Allium sativum L.), and it is known as an allelochemical responsible for the strong allelopathic potential of garlic. The anticancer properties of DADS have been studied in experimental animals and various types of cancer cells, but to date, little is known about its mode of action as an allelochemical at the cytological level. The current research presents further studies on the effects of DADS on tomato (Solanum lycopersicum L.) seed germination, root growth, mitotic index, and cell size in root meristem, as well as the phytohormone levels and expression profile of auxin biosynthesis genes (FZYs), auxin transport genes (SlPINs), and expansin genes (EXPs) in tomato root. The results showed a biphasic, dose-dependent effect on tomato seed germination and root growth under different DADS concentrations. Lower concentrations (0.01–0.62 mM) of DADS significantly promoted root growth, whereas higher levels (6.20–20.67 mM) showed inhibitory effects. Cytological observations showed that the cell length of root meristem was increased and that the mitotic activity of meristematic cells in seedling root tips was enhanced at lower concentrations of DADS. In contrast, DADS at higher concentrations inhibited root growth by affecting both the length and division activity of meristematic cells. However, the cell width of the root meristem was not affected. Additionally, DADS increased the IAA and ZR contents of seedling roots in a dose-dependent manner. The influence on IAA content may be mediated by the up-regulation of FZYs and PINs. Further investigation into the underlying mechanism revealed that the expression levels of tomato EXPs were significantly affected by DADS. The expression levels of EXPB2 and beta-expansin precursor were increased after 3 d, and those of EXP1, EXPB3 and EXLB1 were increased after 5 d of DADS treatment (0.41 mM). This result suggests that tomato root growth may be regulated by multiple expansin genes at different developmental stages. Therefore, we conclude that the effects of DADS on the root growth of tomato seedlings are likely caused by changes associated with cell division, phytohormones, and the expression levels of expansin genes.

Transcriptomic insights into the allelopathic effects of the garlic allelochemical diallyl disulfide on tomato roots

“…The GH3 genes encode a group of enzymes that adenylate IAA or conjugate free IAA with amino acids, thereby inhibiting plant growth. In the present study, the elevated expression of SAURs and decreased expression of GH3 suggest that DADS promotes auxin content, consistent with a previous study19. In addition, auxin could induce the production of H 2 S, which promotes lateral root formation in tomato45.…”

“…In a previous study, we demonstrated that DADS exerts a biphasic, dose-dependent effect on tomato primary root elongation; DADS promoted tomato root elongation at low concentrations (0.01–0.62 mM) but inhibited elongation at high concentrations (6.2–20.67)19. Based on previous studies, we propose that DADS may also play an important role in alleviating the obstacles to continuous cropping of vegetables.…”

Soil Amendment with Raw Garlic Stalk: A Novel Strategy to Stimulate Growth and the Antioxidative Defense System in Monocropped Eggplant in the North of China

“…However, higher doses of RGS inhibited eggplant growth, chlorophyll contents, and most photosynthesis attributes in both years. Garlic reportedly contains organosulfur compounds such as DADS (diallyl disulfides), diallyl trisulfide (DATS), and allicin (strong antioxidants), which at higher concentrations inhibit plant growth and photosynthesis by decreasing chlorophyll contents and root length [38,39]. Similar results were observed in our study in the case of RGS3.…”

Temperature dependence of allelopathy duality and its influence on boreal forest succession-A case analysis of Picea schrenkiana

“…It has been recognized that allelochemicals could be released from plants into the environment through several ways such as volatilization, root exudation, decomposition and leaching to interfere the growth of adjacent plants (Subrahmaniam et al ., 2018). Some allelochemicals could increase cell membrane permeability (Bais et al ., 2003; Chai et al ., 2013), inhibit cell division and elongation, damage cell sumicroscopic structure (Teerarak et al ., 2012; Cheng et al ., 2016), disturb plant photosynthesis and respiration (Yu et al ., 2005), affect synthesis of plant endogenous hormones and proteins (Zeng et al ., 2001; Hu et al ., 2015), and so on. In consequence, allelopathy would potentially influence the growth and development of plants, succession of plant communities (Cummings et al ., 2012; Bonanomi et al ., 2018) and invasion of exotic plant into forest ecosystems (Meiners et al ., 2012).…”