Project description:Soft rot or Rhizopus rot, caused by the fungal pathogen Rhizopus stolonifer, is an aggressive postharvest disease that affects many fruit and vegetables. We proposed that R. stolonifer displays a necrotrophic behavior when infecting fruit, actively killing the host tissues to complete its life cycle. We tested this hypothesis by identifying R. stolonifer infection strategies when interacting with four fruit hosts (tomato, grape, strawberry, and plum). First, we generated a complete and highly contiguous genome assembly for R. stolonifer using PacBio sequencing, of 45.02 Mb in size, an N50 of 2.87Mb, and 12,644 predicted loci with protein-coding genes. We then performed a transcriptomic analysis to identify genes preferentially used by R. stolonifer when growing in fruit versus culture media, and then classified these host-related genes into clusters according to their expression patterns across four time points. Based on the expression data, we determined that R. stolonifer deploys infection mechanisms characteristic of necrotrophs, including a suite of oxidases, proteases, and cell wall degrading enzymes, when it is actively breaking down tissues of all four fruit hosts. Better understanding R. stolonifer – fruit host interactions can support better diagnostic tools and efficient management strategies in postharvest.
Project description:Worldwide, 20-25% of all harvested fruit and vegetables are lost annually in the field and throughout the postharvest supply handling chain due to spoilage by fungal pathogens. Most impactful postharvest pathogens exhibit necrotrophic lifestyles, resulting in rotting of the host tissues and complete loss of marketable commodities. Necrotrophic fungi can readily infect ripe fruit leading to the rapid establishment of disease symptoms. However, these pathogens generally fail to infect unripe fruit, or remain quiescent until host and environmental conditions stimulate a successful infection. Current research on necrotrophic infections of fruit was mainly focused on the host by characterizing genetic and physicochemical factors that inhibit or promote the disease. However, the pathogenicity and virulence strategies employed by necrotrophic pathogens in ripe and unripe fruit are mostly understudied. Here, we provide a first comparative transcriptomics study of fungal postharvest pathogens: Botrytis cinerea, Rhizopus stolonifer and Fusarium acuminatum, all of which display necrotrophic behavior when infecting fruit. We de novo assembled and annotated the transcriptomes of R. stolonifer, and F. acuminatum and performed a differential gene expression analysis comparing the three fungal transcriptomes during fruit infection with that of fungal in-vitro growth. Analysis of the differentially expressed genes for enrichment of functional annotations revealed shared strategies of the three fungi during infection of compatible (ripe fruit) and incompatible (unripe fruit) hosts. We furthermore selected candidate genes that are involved in these strategies to characterize their expression during infection of unripe and ripe-like fruit of the non-ripening (nor) tomato mutant, both of which are physiologically and biochemically similar to unripe wildtype fruit. By enabling a better understanding of fungal necrotrophic infection strategies, we move closer to generating accurate models of fruit diseases and development of early detection tools and effective management strategies.
Project description:The increased susceptibility of ripe fruit to fungal pathogens poses a substantial threat to crop production and marketability. Here, we coupled transcriptomic analyses with mutant studies to uncover critical genes and processes governing ripening-associated susceptibility in tomato (Solanum lycopersicum) fruit. Using wild-type unripe and ripe fruit inoculated with three fungal pathogens—Botrytis cinerea, Fusarium acuminatum, and Rhizopus stolonifer—we identified common pathogen response genes reliant on chitinases, WRKY transcription factors, and reactive oxygen species detoxification. Interestingly, susceptible ripe fruit demonstrated a more extensive defense response than resistant unripe fruit, indicating that the magnitude and diversity of defense response does not significantly impact the interaction. To tease apart individual features of ripening that may be responsible for susceptibility, we utilized three tomato non-ripening mutants: Cnr, rin and nor. Fruit from these mutants displayed different patterns of susceptibility to fungal infection. Functional analysis of the genes altered during ripening in the susceptible genotypes revealed losses in the maintenance of cellular redox homeostasis. Moreover, jasmonic acid accumulation and signaling coincided with the activation of defenses in resistant fruit. Lastly, based on high gene expression in susceptible fruit, we identified and tested two candidate susceptibility factors, pectate lyase (PL) and polygalacturonase (PG2a). CRISPR-based knockouts of PL, but not PG2a, resulted in more than 50% decrease in the susceptibility of ripe fruit, demonstrating that PL is a major susceptibility factor. Ultimately, this study demonstrates that targeting specific genes that drive susceptibility is a viable strategy to improve resistance of tomato fruit against fungal pathogens.
Project description:Blueberry is one of the most desirable and nutritious fruits. During fruit development, the blueberry’s organoleptic properties and phytonutrient composition are ever-changing [1]. Blueberry fruit development is typically described in five phases: pads, cups, green, pink, and blue (ripe) [2]. The former two phases are referred to as the initial “expansion”. During expansion, young fruit is generally hard, dark green and distinguishable by size [3]. The latter three phases are referred to as maturation. Green fruit are hard and fully rounded green berries; pink berries are partially pigmented; blue (ripe) berries are fully colored and soft. Fruit maturation has attracted considerable research attention, and typically, the characteristics fruit softening, coloring, and sweetening are assessed [4].
2019-05-13 | PXD011815 | Pride
Project description:Soft rot pathogens causing disease on Potato
Project description:Adaptation of necrotrophic infection strategies by Botrytis cinerea, Fusarium acuminatum, and Rhizopus stolonifer as a function of tomato fruit ripening
Project description:Tomato phototropin1 mutant exhibits deep red color in the ripe fruits compared to the wild type. However, the mechanisms governing this intense fruit coloration in the mutant are largely unknown. Therefore, a proteomic approach combined with carotenoid profiling and carotenogenic gene expression was used to decipher the carotenogenesis in a tomato phototropin1 mutant with S. lycopersicum, cv. Ailsa Craig (tomato).