Six aquaporin (AQP) homologues were identified in three coffee species (Coffea arabica, C. Canephora, and C. racemosa), including four plasma membrane intrinsic proteins (PIP1;1, PIP1;2, PIP2;1, and PIP2;2) and two tonoplast intrinsic proteins (TIP1;1 and TIP1;2). In order to better understand the role of these genes in coffee, C. arabica cvs Catuaí and Mundo Novo, C. canephora cv. Apoatã, and a graft of Mundo Novo on Apoatã were water stressed, and the expression levels of PIP1;2, PIP2;1, PIP2;2, and TIP1;2 were analyzed in the roots and leaves. The expression of PIP2;1 and PIP2;2 was clearly up-regulated in the leaves and roots by water deficit, suggesting the possible involvement of these genes in controlling the water status of plants and in the post-stress recovery of irrigated plants. The most strongly induced expression in roots was found in both grafted and non-grafted Apoatã plants. Interestingly, the level of PIP2;1 transcripts in roots continued to rise even after the plants were watered and were, therefore, no longer subjected to the water stress, suggesting that this gene may be actively involved in the regulation of water uptake in coffee tree roots, especially when there is a water deficit in the soil.
aquaporins; PIPs; Coffea arabica; Coffea canephora; water stress; root