Efficacy of Allicin against Plant Pathogenic Fungi and Unveiling the Underlying Mode of Action Employing Yeast Based Chemogenetic Profiling Approach

Abstract

Allicin (diallylthiosulfinate) is the principal organosulfur compound present in freshly damaged garlic tissue which exhibits a wide range of biological actions including antibacterial, antifungal, antiviral and anticancer properties. The antifungal activities of allicin were investigated against plant pathogenic fungi of agriculture importance. Furthermore, a yeast genome haploinsufficiency screening was also employed to decipher the antifungal mode of action of allicin. Wildtype and 1152 yeast mutant strains (each deprived of one specific allele of an essential gene in a diploid strain) were screened against allicin. Allicin exhibited promising antifungal properties against all the tested plant pathogens. Haploinsufficiency screening revealed three hypersensitive yeast mutants with gene deletions coding for proteins involved in DNA replication, mitochondrial translation and chromatids cohesion. These processes play a vital role in the cell cycle, growth and viability of yeast cells. Taken together, the results of the present study unravel the excellent antifungal activities and mechanisms and modes of action of allicin. These findings also indicate the potential use of allicin as an alternative “green” fungicide (fumigant) in agriculture.

Antifungal Activity of Propyl-Propane-Thiosulfinate (PTS) and Propyl-Propane-Thiosulfonate (PTSO) from Allium cepa against Verticillium dahliae: In Vitro and in Planta Assays

“…In this context, the broad antimicrobial activity of organosulfur compounds derived from Allium spp. against a variety of bacteria and fungi has already been demonstrated in various in vitro studies [ 10 , 14 , 31 , 42 , 47 ]. Although the mechanism of action of organosulfur compounds is not yet deeply studied, the antimicrobial activity of these compounds could be associated with their capacity to react with the thiol groups of microbial enzymes, RNA synthesis blocking mechanisms, induction of oxidative stress and cellular apoptosis [ 15 , 29 , 30 ].…”

“…As previously mentioned, scientific reports on the activity of organosulfur compounds from onion against plant pathogens are limited. On the contrary, more evidence on the antifungal activity of similar compounds from garlic, such as diallyl thiosulfinate or allicin [ 10 , 42 ] has been found. Some authors have reported the antifungal activity of an allicin against V. dahliae , both in vitro and in a leaf disk bioassay [ 53 ].…”

“…To date, the only method that has proven to be effective against this pathogen is soil disinfection with fumigants such as methyl bromide or chloropicrin. However, the potential risk involved in applying these chemicals, for both human health and the environment, has led to their banning in many countries [ 10 , 11 , 12 ]. The lack of effective fungicides, and the increasing restrictions on the use of chemical compounds in managing plant diseases, is pushing the search for new alternative methods to control V. dahliae [ 8 ].…”

“…In recent years, the antimicrobial activity of several organosulfur compounds such as thiosulfinates and thiosulfonates, obtained from Allium genus plants such as onion ( Allium cepa L.), Welsh onion ( Allium fistulosum L.) or garlic ( Allium sativum L.), has been extensively studied [ 10 , 13 , 14 , 15 , 16 ]. In onion, the most common organosulfur compounds are isoalliin (S-propenyl-L-cysteine sulfoxide) and propiin (S-propyl-L-cysteine sulfoxide).…”

“…When an onion is crushed or cut, propiin changes into propyl-propane thiosulfinate (PTS) due to the action of the enzyme [ 17 ]. Despite the fact PTS is more stable than other thiosulfinates such as allicin [ 10 ], it is also a labile compound that changes into dipropyl disulfide and propyl-propane thiosulfonate (PTSO) [ 18 ].…”