Abstract
SUMMARY The beverage cash crop coffee (Coffea arabica L.) is subject to severe losses caused by the rust fungus Hemileia vastatrix. In naturally resistant coffee plants, a specific hypersensitive reaction (HR) may be elicited early to stop fungal infection. To isolate host genes involved in HR, we undertook an expressed sequence tags (ESTs) analysis. Two cDNA libraries were constructed using suppression subtractive hybridization (SSH) and 527 non-redundant ESTs were generated from 784 randomly picked clones. Classification of the ESTs into several functional categories showed that more than one-quarter of the predicted proteins might encode disease resistance (R) proteins, stress- and defence-proteins, and components of signal transduction pathways. Twenty-eight differentially screened sequences (DSSs) were selected after differential hybridization of 1000 cDNA clones from each library. Investigation of the expression patterns of a subset of 13 DSSs showed higher levels of gene expression in inoculated plants compared with control plants. HR-up-regulation of transcript accumulation occurred for 9 out of the 13 genes 24 and 48 h after H. vastatrix challenge. Two genes encoded homologues of the Arabidopsis DND1 and NDR1 proteins, suggesting conservation of resistance signalling pathways in perennial plants. Other HR-regulated sequences matched receptor kinases, AP2 domain- and WRKY transcription factors, cytochromes P450, heat shock 70 proteins, glucosyltransferases and proteins of unknown function. The ESTs reported here provide a useful resource for studying coffee resistance responses and for improving C. arabica for durable disease resistance.
Highlights
The coffee plant Coffea arabica L. represents one of the key export and cash crops in tropical and subtropical developing countries
Resistant coffee plants challenged by the rust fungus may undergo a typical hypersensitive reaction (HR) at leaf infection sites (Rodrigues et al, 1975; Silva et al, 2002)
We present the first catalogue of C. arabica nonredundant expressed sequence tags (ESTs) and we describe the identification of genes for which expression is regulated during the early events of H. vastatrix infection process
Summary
The coffee plant Coffea arabica L. represents one of the key export and cash crops in tropical and subtropical developing countries. This perennial crop is subject to high losses in potential production due to pests and diseases. Resistant coffee plants challenged by the rust fungus may undergo a typical hypersensitive reaction (HR) at leaf infection sites (Rodrigues et al, 1975; Silva et al, 2002). Growth of the fungus in resistant coffee plants usually ceased 4 days p.i., generally before the formation of the first haustorium (Martins and Moraes, 1996; Silva et al, 2002)
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