Interaction between the Accumulation of Cadmium and Deoxynivalenol Mycotoxin Produced by Fusarium graminearum in Durum Wheat Grains

Abstract

Durum wheat is one of the cereal crops that accumulates the highest concentrations of cadmium (Cd) and deoxynivalenol (DON) mycotoxin in its grains, thereby affecting the safety of products made of durum wheat grains (pasta and semolina). This study investigates in planta the interaction between Cd and Fusarium graminearum, the main causal agent of DON accumulation in grains. A pot experiment was designed to characterize the response of durum wheat to F. graminearum infection at three levels of Cd exposure: 0.1, 2, and 10 mg Cd kg–1 soil, which showed that the accumulation of Cd and DON resulted from interacting processes. On the one hand, plant exposure to Cd reduced the concentration of DON in grains. The mitigating effect of Cd on DON accumulation was attributed to the restricted growth of F. graminearum, which could result from enhanced plant resistance to the fungal pathogen induced by Cd exposure. On the other hand, F. graminearum infection of durum wheat increased the Cd concentration in the grains. The promoting effect of Fusarium infection on Cd accumulation was attributed to decoupling of the allocation of Cd and photoassimilates to the grains and to the reduced strength of the grain sink for photoassimilates caused by the fungus. Provided that this result is confirmed in field conditions, it suggests that in Cd-contaminated soils, particular attention should be paid to agronomic practices that affect Fusarium head blight disease to avoid further increase in the risk of exceeding the regulatory limit set by the European Union for Cd in durum wheat.

Nucleoside Diphosphate Kinase FgNdpk Is Required for DON Production and Pathogenicity by Regulating the Growth and Toxisome Formation of Fusarium graminearum

“…Fusrarium graminearum is a plant pathogen that infects many crop plants, including wheat and barley, and causes Fusarium head blight. − The fungus produces many mycotoxins, including the trichothecenes deoxynivalenol (DON), nivalenol (NIV), and the estrogenic mycotoxin zearalenone . These mycotoxins contaminate grains and cause serious health problems in humans and animals. − In Fusarium species, the enzymes involved in the de novo trichothecene biosynthetic pathway (from acetyl-CoA to DON) have been comprehensively investigated. − Two cytochrome P-450 oxygenases (FgTri1 and FgTri4) localize to spherical organelles, approximately 3 to 4 μm in diameter, that were presumed to be the site for trichothecene biosynthesis. ,, Subsequently, these spherical organelles were named toxisomes, derived from remodeled endoplasmic reticulum (ER) under mycotoxin-inducing conditions. , In recent years, myosin I, actin capping proteins, microtubule, plasma membrane H + -ATPase FgPMA1, venturicidin A, transcription factor FgStuA, and RNA exosome complex were demonstrated to be required for toxisome formation or assembly in F. graminearum. ,− However, the mechanisms of the formation and assembly of the toxisomes are still not well characterized.…”