The Contents of Ustiloxins A and B along with Their Distribution in Rice False Smut Balls

Abstract

Ustiloxins are cyclopeptide mycotoxins isolated from rice false smut balls (FSBs), the ball-like colonies transformed from the individual grains through the filament infection by the fungal pathogen Villosiclava virens. There were no obvious relations between ustiloxin content and any of the collection areas, collection times, or average weight of each FSB. The rice false smut balls at early, middle, and late maturity stages were respectively divided into different parts (glume, chlamydospores, mycelia, and pseudoparenchyma). The highest content of ustiloxins A and B of rice FSBs was found at the early maturity stage. Both ustiloxins A and B were mainly distributed in the middle layer containing mycelia and immature chlamydospores of the FSBs. When the rice FSBs were at the early maturity stage, the total yield of ustiloxins A and B in the middle layer of each ball was 48.3 µg, which was 3.20-fold of the yield (15.1 µg) of the inner part of the ball. The rice FSBs at the early maturity stage are the appropriate materials for the production of ustiloxins A and B.

Structural Diversity and Biological Activities of Fungal Cyclic Peptides, Excluding Cyclodipeptides

“…Ustiloxins ( 286 – 291 ) have a 13-membered ring including a phenol ether linkage. They were isolated from the water extract of the false smut balls caused by Ustilaginoidea virens on the panicles of rice plants [ 208 , 209 , 210 , 211 , 212 ]. There are three amino acids in the core ring for each ustiloxin.…”

A Novel Effector Gene SCRE2 Contributes to Full Virulence of Ustilaginoidea virens to Rice

“…Seven ustiloxin and 26 ustilaginoidin derivatives have been identified and detected in the smut balls and/or in the mycelia so far (Zhou et al, 2012; Fu et al, 2017; Wang et al, 2017). These secondary metabolites, which are toxic to human and animals, reduce grain quality severely (Koyama et al, 1988; Luduena et al, 1994; Nakamura et al, 1994; Li et al, 1995; Shan et al, 2012; Wang et al, 2016; Fu et al, 2017). Recent studies illustrate infection processes of U. virens , including conidial germination on the surface of spikelet, mycelial growth, floral organ infection, and eventual false smut ball formation (Ashizawa et al, 2012; Tang et al, 2013; Hu et al, 2014; Fan et al, 2015; Yong et al, 2018).…”

Development of Colloidal Gold‐Based Lateral Flow Immunoassay for Rapid Qualitative and SemiQuantitative Analysis of Ustiloxins A and B in Rice Samples

“…As UA and UB were the predominant ustiloxins in rice FSBs [15,16], and ustilaginoidins A, D, E and I were main ustilaginoidins in rice FSBs [13,36], thus, UA and UB as well as ustilaginoidins A, D, I and E were chosen to detect the cross reactivities of LFIAs. We also tested the cross reactivities against AFB1, ZEN and DON at concentration of 50,000 ng/mL, as they were the major mycotoxins contaminating grains.…”

“…With the recent widespread cultivation of hybrid rice and heavy application of nitrogenous fertilizer, the rice false smut disease has become significant, resulting in yield loss and grain contamination, and even more importantly, generating mycotoxins (i.e., ustiloxins and ustilaginoidins) that are toxic to plants as well as humans and domestic animals [8,9,10,11,12,13,14]. Ustiloxins, containing a 13-membered cyclic core structure with a phenol ether linkage, were isolated and identified from rice FSBs and named as ustiloxins A, B, C, D, F and G. Among them, ustiloxin A (UA) and ustiloxin B (UB) (Figure 1) are the most toxic and represent more than 80% of the total ustiloxin content [15,16]. It has been reported that ustiloxins had antimitotic activity by inhibiting microtubule assembly and cell skeleton formation of plant and animal cells [17,18,19,20,21].…”