Caracterização in silico e análise da expressão de genes das rotas de biossíntese e sinalização do etileno em frutos de diferentes cultivares de café (coffea arabica) / In silico characterization and expression analysis of genes of the ethylene biosynthesis and signaling pathways in fruits of different coffee (Coffea arabica) cultivars

André Almeida Lima

Coffee is the second most commercialized product in the world posing as an important source of income and jobs in several countries, mainly in developing countries such as Brazil, the largest producer and the second largest consumer of coffee in the world. Coffee quality, among other factors, is directly associated to the fruit ripening stage at harvest time, which is often highly asynchronous due to the sequential flowering found in coffee trees, and usually leads to a higher production costs and also a lower cup quality. Some studies suggest that coffee may constitute a climateric fruit indicating that ethylene plays an important role in the coffee fruit ripening process. Coffee early cultivars usually show a more uniform ripening process although little is known about the genetic factors that promote the earliness of ripening. Thus, this study aimed to in silico characterize the putative genes of the ethylene biosynthesis and signaling pathways and to analyze the expression of some of these genes during the fruit ripening process of a late (Acauã) and an early (Catucaí 785-15) coffee cultivars. The selected sequences obtained from the searches performed in the CAFEST database had their phylogeny assessed by phylogenetic trees and their in silico expression profiles were analysed by electronic Northerns. Coffee fruits were harvested in the periods from March to June of 2008 and 2009 with an interval of approximately 30 days between each harvest and the gene expression analyses were carried out by qRT-PCR. The CAFEST database showed a high number of sequences related to the genes of the ethylene biosynthesis and signaling pathways allowing the identification of putative members from almost every step of them. The phylogenetic trees demonstrated a high similarity between the sequences found in the CAFEST and those form other species, and the electronic Northerns detected their expression in different tissues, development stages and stress conditions. The expression analyses of the genes encoding a putative ACO (CaACO3) and a putative ethylene receptor (CaETR4) showed that these genes are differentially expressed through the ripening process, with higher expression levels found at the times in which a major percentage of fruits in the light-red and cherry colors were present for both cultivars. The putative ERF transcription factor (CaERF4) seems to show an increased expression level throughout the experiment and were not differentially expressed during the fruit ripening period of both studied cultivars.

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