Brown rot (BR) caused by Monilinia spp., has been an economic problem for the stone fruit market due to dramatic losses, mainly during the postharvest period. There is much literature about basic aspects of Monilinia spp. infection, which indicates that environment significantly influences its occurrence in the orchard. However, progress is needed to sustainably limit this disease: the pathogen is able to develop resistance to pesticides, and most of BR resistance research programs in plant models perish. Solving this problem becomes important due to the need to decrease chemical treatments and reduce residues on fruit. Thus, research has recently increased, exploring a wide range of disease control strategies (e.g., genetic, chemical, physical). Summarizing this information is difficult, as studies evaluate different Monilinia and Prunus model species, with diverse strategies and protocols. Thus, the purpose of this review is to present the diversity and distribution of agents causing BR, focusing on the biochemical mechanisms of Monilinia spp. infection both of the fungi and of the fruit, and report on the resistance sources in Prunus germplasm. This review comprehensively compiles the information currently available to better understand mechanisms related to BR resistance.

The Bacillus cereus spore surface layers consist of a coat surrounded by an exosporium. We investigated the interplay between the sporulation temperature and the CotE morphogenetic protein in the assembly of the surface layers of B. cereus ATCC 14579 spores and on the resulting spore properties. The cotE deletion affects the coat and exosporium composition of the spores formed both at the suboptimal temperature of 20°C and at the optimal growth temperature of 37°C. Transmission electron microscopy revealed that ⌬cotE spores had a fragmented and detached exosporium when formed at 37°C. However, when produced at 20°C, ⌬cotE spores showed defects in both coat and exosporium attachment and were susceptible to lysozyme and mutanolysin. Thus, CotE has a role in the assembly of both the coat and exosporium, which is more important during sporulation at 20°C. CotE was more represented in extracts from spores formed at 20°C than at 37°C, suggesting that increased synthesis of the protein is required to maintain proper assembly of spore surface layers at the former temperature. ⌬cotE spores formed at either sporulation temperature were impaired in inosine-triggered germination and resistance to UV-C and H 2 O 2 and were less hydrophobic than wild-type (WT) spores but had a higher resistance to wet heat. While underscoring the role of CotE in the assembly of B. cereus spore surface layers, our study also suggests a contribution of the protein to functional properties of additional spore structures. Moreover, it also suggests a complex relationship between the function of a spore morphogenetic protein and environmental factors such as the temperature during spore formation. Bacterial endospores are formed in a wide range of ecological niches in soil, as well as in the gastrointestinal tract of invertebrate and vertebrate animals, and in both natural and anthropized environments (1). Physical and chemical conditions prevailing in such niches play a major role in triggering sporulation and in determining the final properties of the resulting spores (2). Laboratory experiments demonstrate the major influence of environment, in particular of temperature, on the efficiency and yield of sporulation, and in spore resistance to wet heat, UV, high hydrostatic pressure, and preservatives or spore response to germinants (3; reviewed in references 1 and 4). Spore resistance and functional properties result from the assembly of several protective structures: cortex, coat, and exosporium. The spore peptidoglycan cortex, a structure common to all endospores, is a major factor in the resistance of spores to heat (1, 4). The cortex is surrounded by a proteinaceous coat, and in organisms such as Bacillus anthracis or Bacillus cereus the coat is further enveloped by an exosporium, a "balloon-like" structure consisting of a paracrystalline basal layer and an external hair-like nap formed mainly by the collagen-like glycoprotein BclA (5-11). While the coat contributes to protection against peptidoglycan-breaking enzymes, UV light, and oxidative...

Bacillus cereus ATCC 14579 possesses five RNA helicase-encoding genes overexpressed under cold growth conditions. Out of the five corresponding mutants, only the ⌬cshA, ⌬cshB, and ⌬cshC strains were cold sensitive. Growth of the ⌬cshA strain was also reduced at 30°C but not at 37°C. The cold phenotype was restored with the cshA gene for the ⌬cshA strain and partially for the ⌬cshB strain but not for the ⌬cshC strain, suggesting different functions at low temperature.

No abstract

No abstract