This section presents a summary of the RNA-seq libraries that are available in this database. Please, download the “Samples List” file for more detailed information about each library and experiment. Feel free to contact us with any queries.
INFECTED SHOOTS (BROOMS)
Infection of cacao shoots by Moniliophthora perniciosa results in the typical symptoms of WBD, including the formation of abnormal shoots (brooms) that display great morphological alterations. The available libraries cover four different stages of the infection in seedlings (green broom, initial necrosis, advanced necrosis and dry broom) and allow the simultaneous analysis of both cacao and M. perniciosa genes during their interaction. Healthy, age-matched cacao plants were sampled as controls.
The fungus Moniliophthora perniciosa is also able to infect the fruits of its cacao host, initially causing swelling and abnormal ripening and later resulting in the death of the infected tissues. The transcriptional analysis of fruits infected by M. perniciosa provides insight into the infection process in a second cacao tissue. In this experiment, fruits at three different stages of the disease were harvested from a cacao farm in Ilhéus (Bahia, Brazil). Libraries were prepared from both the beans and the shells of each pod. Healthy fruits were also harvested.
IN VITRO MYCELIAL DEVELOPMENT
As a hemibiotroph, Moniliophthora perniciosa initially infects the living cacao plant as a bioptroph and later colonizes the dead plant tissues as a necrotroph. Interestingly, these two life stages are morphologically distinct; whereas the biotrophic mycelium is composed of swollen monokaryotic cells, the necrotrophic hyphae are thinner, dikaryotic and have clamp connections for nuclei transfer. To date, the mechanisms that regulate the lifestyle transition in M. perniciosa are poorly understood. The WBD Transcriptome Atlas includes libraries constructed from both monokaryotic and dikaryotic mycelia under in vitro conditions. Three different time-points during fungal development were sampled (7, 14 and 28 days post inoculation).
Moniliophthora perniciosa is a basidiomycete fungus that produces mushrooms as reproductive structures. After extended colonization of the living cacao tissues, the pathogen switches to necrotrophic growth and colonizes the dead plant tissues. Following intermittent dry and wet periods, the necrotrophic mycelia produce basidiomata, thus completing the fungal life cycle. The WBD Transcriptome Atlas includes libraries that represent two different stages of the M. perniciosa reproductive structure, i.e., primordia and mature basidiomata. These samples were obtained under laboratory conditions following a modified version of the protocol described by Griffth & Hedger (1993).
Basidiospores are the only known Moniliophthora perniciosa structures capable of initiating infection in the host plant. When released by the mushrooms, spores germinate on the surface of the cacao tree and penetrate the plant through stomata or wounds. Since these structures are closely associated with the initial infection process and with the establishment of the disease, transcriptional analyses of spores may support the identification of genes with major roles in M. perniciosa virulence. The libraries included in the WBD Transcriptome Atlas v1.0 represent non-germinated spores and spores germinated in water for 4 h.
FUNGAL GROWTH IN SPECIFIC CARBON SOURCES
During the progression of WBD, the quantity and quality of nutrients that are available for the pathogen vary considerably. The regulation of Moniliophthora perniciosa development and virulence appears to be directly coupled with the nutritional status encountered during host colonization. As a resource to investigate the effects of carbon sources on the transcriptional regulation of this pathogen, the WBD Transcriptome Atlas includes RNA-seq libraries representing the fungus exposed to six different carbon sources under laboratory conditions: glucose, glycerol, pectin, polygalacturonic acid, methanol and cacao extract.
TREATMENT WITH DRUGS
Despite numerous efforts, there are still no methods to effectively control WBD. Remarkably, Moniliophthora perniciosa can naturally tolerate high concentrations of strobilurins, one of the most widely used classes of fungicides in agriculture. These drugs are potent inhibitors of the fungal mitochondrial respiratory chain, leading to the generation of reactive oxygen species and the reduction of energy production. Importantly, the enzyme alternative oxidase (AOX) plays an important role in fungal resistance against inhibitors of the respiratory chain. As a resource to improve our understanding of drug resistance in M. perniciosa, the WBD Transcriptome Atlas v1.0 includes transcriptomes of this fungus treated in vitro with the strobilurin Azoxistrobin, the AOX inhibitor SHAM (salicylhydroxamic acid) and combinations of both drugs.