The C4 protein of tomato yellow leaf curl Sardinia virus is involved in drought stress tolerance of tomato plants

Viruses were recently shown to interfere with the response of plants to abiotic stresses, indicating the existence of common molecular networks that regulate the reaction of plants to biotic and abiotic stresses. We investigated the basis of such networks within the ever-expanding group of begomoviruses causing the tomato yellow leaf curl disease, which were shown to promote drought tolerance in Arabidopsis and heat tolerance in tomato. Combining morphometric, ecophysiological, biochemical, and molecular analyses, we observed that the C4 protein of tomato yellow leaf curl Sardinia virus positively affects drought stress tolerance in transgenic tomato plants overexpressing it. In these plants, a delayed onset of drought-stress related physiological responses occurred, followed by a faster post-stress recovery. Transcriptional and biochemical data on the main hormone metabolic pathways controlling drought stress responses were analyzed, trying to understand if viral proteins can determine beneficial growth-defence trade-offs in tomato plants. This study provides novel information on the biological mechanisms underlying the tolerance of transgenic tomato plants to drought, which might have particular importance in the context of managing the effects of future climate changes on agricultural systems.