No abstract

A biocontrol method plays an important role in weed management. In this study, we aimed to clarify the phytotoxicity of the mycotoxin patulin (PAT) and reveal its mode of action as a new natural photosystem II (PSII) inhibitor. Phytotoxicity test showed that PAT has herbicidal activity and causes significant leaf lesions on Ageratina adenophora. Under a halfinhibition concentration I 50 (2.24 μM), the observed significant decrease in oxygen evolution rate and the increase in the J-step of the chlorophyll fluorescence rise OJIP curve indicated that PAT strongly reduces photosynthetic efficiency by blocking electron transport from the primary to secondary plastoquinone acceptors (Q A to Q B ) of PSII. Molecular modeling of PAT docking to the A. adenophora D1 protein suggested that PAT bounds to the Q B site by forming hydrogen bonds to histidine 252 in the D1 protein. It is proposed that PAT is a new natural PSII inhibitor and has the potential to be developed into a bioherbicide or used as a template scaffold for discovering novel derivatives with more potent herbicidal activity.

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.

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Large amounts of sugar are imported into grape berries from source leaves during ripening, and sucrose transporters play a key role during this process. In this study, a putative grape sucrose transporter gene VvSUC27, primarily expressed in sink tissue, was transformed into a yeast strain to characterize its function as a sucrose transporter. Sucrose was taken up by yeast transformed with VvSUC27 at an optimum pH of 4.0-5.0 and a K m of 8.0-10.5 mM, indicating VvSUC27 is a LAHC (low-affinity/high-capacity) sucrose transporter. The ability of sucrose uptake in transformed yeast was activated by monosaccharides and inhibited by maltose and DEPC.