Abstract
Alternaria is a ubiquitous fungal genus in many ecosystems, consisting of species and strains that can be saprophytic, endophytic, or pathogenic to plants or animals, including humans. Alternaria species can produce a variety of secondary metabolites (SMs), especially low molecular weight toxins. Based on the characteristics of host plant susceptibility or resistance to the toxin, Alternaria phytotoxins are classified into host-selective toxins (HSTs) and non-host-selective toxins (NHSTs). These Alternaria toxins exhibit a variety of biological activities such as phytotoxic, cytotoxic, and antimicrobial properties. Generally, HSTs are toxic to host plants and can cause severe economic losses. Some NHSTs such as alternariol, altenariol methyl-ether, and altertoxins also show high cytotoxic and mutagenic activities in the exposed human or other vertebrate species. Thus, Alternaria toxins are meaningful for drug and pesticide development. For example, AAL-toxin, maculosin, tentoxin, and tenuazonic acid have potential to be developed as bioherbicides due to their excellent herbicidal activity. Like altersolanol A, bostrycin, and brefeldin A, they exhibit anticancer activity, and ATX V shows high activity to inhibit the HIV-1 virus. This review focuses on the classification, chemical structure, occurrence, bioactivity, and biosynthesis of the major Alternaria phytotoxins, including 30 HSTs and 50 NHSTs discovered to date.
Highlights
The fungal genus Alternaria is a widespread and successful group growing in diverse environments worldwide, ranging from saprophytes to pathogens and even endophytes.The genus Alternaria was identified in the year 1816 [1]
2007, a bacterial artificial chromosome (BAC) was isolated containing four AMT genes and other genes that are upregulated in AM-toxin-producing cultures, suggesting that genes for AM-toxin biosynthesis are clustered in the genome
Alternaria is a ubiquitous genus in many ecosystems, consisting of saprophytic, pathogenic, and even endophytic species
Summary
The fungal genus Alternaria is a widespread and successful group growing in diverse environments worldwide, ranging from saprophytes to pathogens and even endophytes. As an outstanding group of fungal pathogens, Alternaria species can either cause diseases in a wide range of economically important crops [1], resulting in significant economic losses, or affect human and animal health, such as through upper respiratory tract infections and asthma [4,5]. Over 70 toxins with different chemical structures and behaviors are known to be produced by Alternaria species [6]. These toxins often exhibit a variety of bioactivities, such as phytotoxic, cytotoxic, and antimicrobial properties, etc. Alternaria phytotoxins are divided into host-selective toxins (HSTs) and non-host-selective toxins (NHSTs) based on the susceptibility or resistance of the host. The phytotoxins presented in the paper will be termed “toxins”, and those toxic to animals will be termed “mycotoxins”
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