Cytokinin Modulates Responses to Phytomelatonin in Arabidopsis thaliana under High Light Stress

Abstract

Fine-tuned interactions between melatonin (MT) and hormones affected by environmental inputs are crucial for plant growth. Under high light (HL) conditions, melatonin reduced photodamage in Arabidopsis thaliana and contributed to the restoration of the expression of the cytokinin (CK) synthesis genes IPT3, IPT5 and LOG7 and genes for CK signal transduction AHK2,3 and ARR 1, 4, 5 and 12 which were downregulated by stress. However, CK signaling mutants displayed no significant changes in the expression of CK genes following HL + MT treatment, implying that a fully functional cytokinin signaling pathway is a prerequisite for MT–CK interactions. In turn, cytokinin treatment increased the expression of the key melatonin synthesis gene ASMT under both moderate and HL in wild-type plants. This upregulation was further accentuated in the ipt3,5,7 mutant which is highly sensitive to CK. In this mutant, in addition to ASMT, the melatonin synthesis genes SNAT and COMT, as well as the putative signaling genes CAND2 and GPA1, displayed elevated transcript levels. The results of the study suggest that melatonin acts synergistically with CK to cope with HL stress through melatonin-associated activation or repression of the respective hormonal genes.

Special Issue “Phytohormones: Important Participators in Plant Growth and Development”

“…Cytokinins, in turn, affect plant resistance to high light stress due to their effects on the expression of genes involved in melatonin synthesis. The article by Bychkov et al [7] describes the effects of high light stress and melatonin on the genes encoding isopentenyltransferase, which catalyzes the transfer of the isopentenyl group to adenine nucleotide, thereby producing cytokinin (isopentenyladenine) [44,45], LOG gene encoding cytokinin riboside 5 ′ -monophosphate phosphoribohydrolase, which releases free cytokinin base from its nucleotide in one step [46], and other genes involved in cytokinin metabolism and signaling [47]. The authors of [7] consider cytokinins to be contributors to stress tolerance [48][49][50], especially to light stress [51].…”

“…Important developmental processes like shoot branching [5], deposition of lignin and suberin and the formation of apoplastic barriers [6] are the topics of some papers. Several articles address the involvement of classical hormones (cytokinins [6,7], auxins [8][9][10], abscisic acid and gibberellins [4]) in the regulation of plants growth and development. This collection also contains reports on the action of plant growth regulators recently classified as phytohormones: strigalactones [5] and melatonin [3,7].…”

“…Several articles address the involvement of classical hormones (cytokinins [6,7], auxins [8][9][10], abscisic acid and gibberellins [4]) in the regulation of plants growth and development. This collection also contains reports on the action of plant growth regulators recently classified as phytohormones: strigalactones [5] and melatonin [3,7]. Hormonal control of plant growth and development is discussed in connection with the development of plant resistance to stress conditions [5,7,11].…”

“…This collection also contains reports on the action of plant growth regulators recently classified as phytohormones: strigalactones [5] and melatonin [3,7]. Hormonal control of plant growth and development is discussed in connection with the development of plant resistance to stress conditions [5,7,11]. The novelty of the collection presented in this SI lies in demonstrating new aspects of hormonal control of physiological processes: the disturbance of hormonal balance in a maize mutant characterized by unusually large embryo [2], the involvement of ABA in the control of the movement of water lily flower petals [1], melatonin-induced increase in cherimoya fruit resistance to chilling [3], hormonal control of accumulation of storage proteins in Yellow lupin [4], identification of genes responsible for the synthesis of strigolactones in Chimonanthus praecox and their involvement in shoot branching [5], discovery of cytokinin ability to slow down the formation of Casparian bands in transgenic tobacco plants [6] and interaction of cytokinins with melatonin in the control of plant resistance to high light stress [7], identification of the YUCCA genes in Mikania micrantha [8], regulation of PIN-formed (PIN) auxin transporters by their degradation [9], interaction of hormonal and electrical signals in plants [11].…”

“…The topic of control of plant tolerance by melatonin is continued in the article by Bychkov and co-authors [7], which describes the interaction of cytokinins with melatonin in the control of plant resistance to high light stress. It is suggested that a melatonin-induced reduction in the photo-damage of Arabidopsis plants can be partially explained by the effects of melatonin on the expression of the genes responsible for cytokinin metabolism and signaling.…”