Yu Zhang

Anthracnose caused by Colletotrichum spp. is a widespread fungal disease that is detrimental to tobacco growth and inflicts economic damage of up to 100 million in tobacco-growing regions in China. An early diagnostic tool is vital for the accurate determination and management of anthracnose in the field. This study investigated the diversity of Colletotrichum spp. on tobacco leaves with anthracnose and developed a recombinase polymerase amplification–lateral flow dipstick (RPA-LFD) diagnostic method for the rapid and equipment-independent detection of the main Colletotrichum spp. causing tobacco anthracnose. This assay targeted the chitin synthase gene (chs1) and could be performed in a few minutes (6 to 10 min). All isolates of C. karstii, C. fructicola, and C. gloeosporioides yielded positive results in the RPA-LFD assay, and no cross-reaction occurred with other fungal species from tobacco or other hosts. The detection threshold was 1 pg of genomic DNA under optimal reaction conditions. The entire RPA-LFD assay enabled the detection of pathogen visualization within 30 min without specialized equipment by combining a polyethylene glycol-KOH method for extracting gDNA rapidly from tobacco leaves infected with C. karstii, C. fructicola, and C. gloeosporioides. Based on these results, the RPA-LFD assay is easy to operate, rapid, and equipment-independent and is promising for development as a kit to diagnose tobacco anthracnose in resource-limited settings at point-of-care.

In model fungi, mitochondrial transport proteins (MTPs), also known as “mitochondrial carriers” (MC), are known to facilitate the exchange of biochemical substances across the mitochondrial inner membrane. In this study, we characterized an MTP in Botrytis cinerea homologous to the known MTPs in Saccharomyces cerevisiae designated BcMtp1. The BcMtp1 deletion mutant phenotype was strikingly defective in vegetative development, conidiation, and sclerotia production. In addition, ΔBcMtp1 showed increased sensitivity to osmotic stress, oxidative stress, and cell wall biogenesis inhibitors. In the pathogenicity assay, ΔBcMtp1 displayed compromised virulence on various host-plant tissues. The BcMtp1 deletion mutant phenotype was rescued by transforming the wild-type BcMtp1 variant into the mutant. Together, these data indicate that BcMtp1 is critical for vegetative development, asexual reproduction, stress tolerance, and virulence of B. cinerea.

Smi1 is a protein required for cell cycle progression, morphogenesis, stress response and life span of Saccharomyces cerevisiae. FaSmi1 was identified as a Smi1 homolog in a wheat scab pathogenic fungus Fusarium asiaticum strain 2021. The deletion of FaSmi1 leads to defects in mycelial growth, asexual reproduction, and virulence. The FaSmi1 deletion mutant also exhibited increased sensitivity to osmotic stresses generated by NaCl and KCl, but increased tolerance to oxidative stresses and cell wall integrity inhibitors. All of these defects were restored by genetic complementation of the mutant with the whole parental FaSmi1 gene. Interestingly, the antioxidant system-associated genes exhibit a lower expression level and the mycotoxins’ DON content was decreased in the FaSmi1 deletion mutant compared with the parental strain 2021. These results indicate that FaSmi1 plays a critical role in the vegetative development, asexual reproduction, DON production and virulence of F. asiaticum.