Expression analysis of transcription factors from the interaction between cacao and Moniliophthora perniciosa (Tricholomataceae).

Cacao (Theobroma cacao) is one of the most important tropical crops; however, production is threatened by numerous pathogens, including the hemibiotrophic fungus Moniliophthora perniciosa, which causes witches' broom disease. To understand the mechanisms that lead to the development of this disease in cacao, we focused our attention on cacao transcription factors (TFs), which act as master regulators of cellular processes and are important for the fine-tuning of plant defense responses. We developed a macroarray with 88 TF cDNA from previously obtained cacao-M. perniciosa interaction libraries. Seventy-two TFs were found differentially expressed between the susceptible (Catongo) and resistant (TSH1188) genotypes and/or during the disease time course--from 24 h to 30 days after infection. Most of the differentially expressed TFs belonged to the bZIP, MYB and WRKY families and presented opposite expression patterns in susceptible and resistant cacao-M. perniciosa interactions (i.e., up-regulated in Catongo and down-regulated in TSH1188). The results of the macroarray were confirmed for bZIP and WRKY TFs by real-time PCR. These differentially expressed TFs are good candidates for subsequent functional analysis as well as for plant engineering. Some of these TFs could also be localized on the cacao reference map related to witches' broom resistance, facilitating the breeding and selection of resistant cacao trees.

Preliminary analysis of expressed sequences of genes in Genipa americana L. plant roots exposed to cadmium in nutrient solution.

Many cell functions are redundantly executed in cells, and the experimental approaches that analyze the group of proteins, whose expression is modified in a specific functional condition, enable the identification of the group of proteins that are expressed under stress conditions. The objective of the present study was the evaluation of the genetic expression induced by cadmium (Cd) in Genipa americana L. (Rubiaceae) plants cultivated in nutritive solution, in order to help further studies concerning its use as a plant phytoremediator of such a metallic element. Plants were exposed to increasing concentrations of Cd (0.5, 1, 2, 4, 8, and 16 mg/L), together with the control, in nutritive solution. After the application of the treatments, root tips were harvested for the construction of a cDNA library. Of the 165 expressed sequence tags (ESTs) generated with the construction of the cDNA library, 81 showed homology to genes deposited in the NCBI database, 67 did not show similarity to any available gene, and 17 ESTs demonstrated homology with unknown genes. Of the most abundant cDNAs, 16 ESTs were similar to sequences of metallothionein genes. The analysis of ESTs, obtained from the root of G. americana through the construction of a cDNA library, allowed the identification of genes probably associated with proteins and enzymes related to the defense mechanisms of plants when they undergo biotic and abiotic stresses.