Dehydrins Are Highly Expressed in Water-Stressed Plants of Two Coffee Species

Drought is the main limiting factor for coffee productivity. In this study, we evaluated the relationship between dehydrins (DHN) and water status in Coffea arabica cvs. Catuaí and Mundo Novo, C. canephora cv. Apoatã, and a graft of Mundo Novo shoot on Apoatã root. The plants were control stressed to achieve a water potential (ψw) of approximately −2.15 ± 0.05 MPa at predawn (6:00 am). Measurements of ψw on the preceding day (at 12:00 noon) and at predawn showed that the Arabicas had greater losses of shoot and root dry mass. Additionaly, proline increased in roots and leaves of all plants, indicating stress establishment. Two DHN unigenes in C. arabica (CaDHN1 and CaDHN3) and one in C. racemosa (CrDHN1) were identified from an expressed sequence tag database with greater than 95 % identity. Three DHN genes named CcDH1, CcDH2, and CcDH3 isolated in previous work from coffee fruits of C. canephora were analysed in this study too. Transcripts of DHN1, DHN2, and DHN3 accumulated in roots and leaves of stressed plants and also in cell suspension cultures of Catuaí stressed with PEG-8000. While DHN1 and DHN3 exhibited basal expression levels, DHN2 was exclusively expressed in stressed plants. Although DHN unigenes were induced by water stress, the expression pattern of each unigene was spatially (leaves and roots) and temporally (distinct stress levels) differentiated, as was the intensity of the responses among the Arabicas, Apoatã, and MN/Apoatã plants. Our results suggest a strong relationship between DHN expression and water stress in coffee.