Interplay of stress responses to carbamazepine treatment, whitefly infestation and virus infection in tomato plants

Abstract

Reclaimed wastewater is increasingly used to irrigate agriculture crops. We have previously shown that carbamazepine (CBZ), an anticonvulsant human medication, not entirely discarded during wastewater purification, induces a stress response in tomatoes grown with roots bathing in CBZ-containing water. Induction of stress-related osmoprotectants (sugars, amino acids, proteins) was conspicuous in CBZ-treated seedlings. Here, tomato seedlings were grown in pots watered with increasing concentrations of CBZ. Soluble sugars effectively reacted to CBZ in both leaves and roots. However, the induction of stress-related amino acids and proteins was relevant in roots, but insignificant in leaves. Therefore, roots may be the site where CBZ stress is exerted. Moreover, roots may protect the whole plant from the pharmaceutical. Tomato crops endure biotic stresses, caused by whitefly (Bemisia tabaci) infestation and by the tomato yellow leaf curl begomovirus (TYLCV) they vector. The interplay between CBZ, TYLCV infection and B. tabaci was studied in tomato. Whiteflies preferred CBZ-treated plantlets than control plants, which may be due to increased amount of sugars in leaves. The increased amount of viruliferous whiteflies on CBZ-treated plants is expected to be accompanied by a rise in virus amounts. In fact, CBZ caused a reduction of TYLCV amounts. CBZ-dependent activation of autophagy degradation may explain this decrease in virus amounts. TYLCV infection mitigates the activation of stress markers associated with CBZ treatment. Altogether, CBZ in the water used to irrigate tomatoes grown in pots causes a relatively weak plant stress response, but is definitively sensed by insect and by virus.