PŘEROSTOVÁ, Sylva, DOBREV, Petre, GAUDINOVÁ, Alena, KNIRSCH, Vojtěch, KÖRBER, N., PIERUSCHKA, R., FIORANI, F., BRZOBOHATÝ, Břetislav, ČERNÝ, M., SPÍCHAL, Lukáš, HUMPLÍK, Jan, VANĚK, Tomáš, SCHURR, U., VAŇKOVÁ, Radomíra. Cytokinins: Their impact on molecular and growth responses to drought stress and recovery in arabidopsis. Frontiers in Plant Science. 2018, 9(MAY 22), 655. ISSN 1664-462X. E-ISSN 1664-462X

Our phenotyping and hormonal study has characterized the role of cytokinins (CK) in the drought and recovery responses of Arabidopsis thaliana. CK down-regulation was achieved by overexpression of the gene for CK deactivating enzyme cytokinin oxidase/dehydrogenase (CKX): constitutive (35S:CKX) or at the stress onset using a dexamethasone-inducible pOp/LhGR promoter (DEX:CKX). The 35S:CKX plants exhibited slow ontogenesis and higher expression levels of stress-associated genes, e.g., AtP5CS1, already at well-watered conditions. CK down-regulation resulted during drought in higher stress tolerance (indicated by relatively low up-regulation of the expression of drought stress marker gene AtRD29B) accompanied with lower leaf water loss. Nevertheless, these plants exhibited slow and delayed recovery after re-watering. CK levels were increased at the stress onset by stimulation of the expression of CK biosynthetic gene isopentenyl transferase (ipt) (DEX:IPT) or by application of exogenous CK meta-topolin. After water withdrawal, long-termCK elevation resulted in higher water loss in comparison with CKX transformants as well as with plants overexpressing ipt driven by senescence-inducible SAG12 promoter (SAG:IPT), which gradually enhanced CKs during the stress progression. In all cases, CKup-regulation resultedin fast andmore vigorous recovery. All drought-stressed plants exhibited growth suppression associated with elevation of abscisic acid and decrease of auxins and active CKs (with the exception of SAG:IPT plants). Apart from the ipt overexpressers, also increase of jasmonic and salicylic acid was found.