The Anti-Senescence Activity of Cytokinin Arabinosides in Wheat and Arabidopsis Is Negatively Correlated with Ethylene Production

Abstract

Leaf senescence, accompanied by chlorophyll breakdown, chloroplast degradation and inhibition of photosynthesis, can be suppressed by an exogenous application of cytokinins. Two aromatic cytokinin arabinosides (6-benzylamino-9-β-d-arabinofuranosylpurines; BAPAs), 3-hydroxy- (3OHBAPA) and 3-methoxy- (3MeOBAPA) derivatives, have recently been found to possess high anti-senescence activity. Interestingly, their effect on the maintenance of chlorophyll content and maximal quantum yield of photosystem II (PSII) in detached dark-adapted leaves differed quantitatively in wheat (Triticum aestivum L. cv. Aranka) and Arabidopsis (Arabidopsisthaliana L. (Col-0)). In this work, we have found that the anti-senescence effects of 3OHBAPA and 3MeOBAPA in wheat and Arabidopsis also differ in other parameters, including the maintenance of carotenoid content and chloroplasts, rate of reduction of primary electron acceptor of PSII (QA) as well as electron transport behind QA, and partitioning of absorbed light energy in light-adapted leaves. In wheat, 3OHBAPA had a higher protective effect than 3MeOBAPA, whereas in Arabidopsis, 3MeOBAPA was the more efficient derivative. We have found that the different anti-senescent activity of 3OHBAPA and 3MeOBAPA was coupled to different ethylene production in the treated leaves: the lower the ethylene production, the higher the anti-senescence activity. 3OHBAPA and 3MeOBAPA also efficiently protected the senescing leaves of wheat and Arabidopsis against oxidative damage induced by both H2O2 and high-light treatment, which could also be connected with the low level of ethylene production.

New Water-Soluble Cytokinin Derivatives and Their Beneficial Impact on Barley Yield and Photosynthesis

“…We have previously shown that leaf senescence is accompanied by chlorophyll degradation and significant damage to photosynthetic functionality 48,49 and that some CK derivatives seem to protect against this degradation. 50,51 We investigated the antisenescent properties of CK mesylates by studying their effects on the photosynthetic apparatus of barley, and concurrently, we captured the deleterious effects of detachment and DMSO exposure on the photosynthetic activity of barley leaves. Such effects seemed pronounced due to the high water solubility of the new CK mesylates, which enables their application without prior dissolution in DMSO.…”

“…Variables determined were the maximum quantum yield of PSII photochemistry in the dark-adapted state, F V /F M ; the initial slope of the O-J chlorophyll fluorescence rise, (dV/dt) 0 ; the relative variable fluorescence at the J step, V J ; and the specific energy flux, ABS/RC. 35,50 The quenching analysis was performed using a FluorCam 700 MF imaging system (Photon Systems Instruments, Czech Republic). Detached segments or attached leaves were placed on a wet filter paper on a plate, with their adaxial side facing the FluorCam camera.…”

Dissecting the Molecular Regulation of Natural Variation in Growth and Senescence of Two Eutrema salsugineum Ecotypes

“…In addition to ethylene, other plant hormones such as cytokinins and auxins also affect leaf senescence. However, unlike ethylene, both cytokinin and auxin can delay leaf senescence [ 73 , 74 ]. The results also showed that the levels of cytokinin and auxin (IAA) in the XJ ecotype leaves were significantly lower than those of the SD ecotype leaves, consistent with their different leaf senescence symptoms ( Figure 1 H and Figure 2 E).…”

Diverse Effect of Two Cytokinins, Kinetin and Benzyladenine, on Plant Development, Biotic Stress Tolerance, and Gene Expression

“…BA treatment suppressed the necrotic disease symptoms and membrane damage (Figure 6). Since cytokinins inhibit leaf senescence [60,61] and necrotrophic pathogens prefer the senescent older plant tissues, therefore, not only the necrotic symptoms but the development of the pathogen is also suppressed in juvenile tissues [23,28].…”