Programmed cell death induced by high levels of cytokinin in Arabidopsis cultured cells is mediated by the cytokinin receptor CRE1/AHK4

Dipartimento di Biologia, Università Degli Studi di Padova, Padua, Italy.
Journal of Experimental Botany (Impact Factor: 5.53). 02/2012; 63(7):2825-32. DOI: 10.1093/jxb/ers008
Source: PubMed


High levels of cytokinins (CKs) induce programmed cell death (PCD) both in animals and plant cells. High levels of the CK
benzylaminopurine (BA) induce PCD in cultured cells of Arabidopsis thaliana by accelerating a senescence process characterized by DNA laddering and expression of a specific senescence marker. In this
report, the question has been addressed whether members of the small family of Arabidopsis CK receptors (AHK2, AHK3, CRE1/AHK4) are required for BA-induced PCD. In this respect, suspension cell cultures were produced
from selected receptor mutants. Cell growth and proliferation of all receptor mutant and wild-type cell cultures were similar,
showing that the CK receptors are not required for these processes in cultured cells. The analysis of CK metabolites instead
revealed differences between wild-type and receptor mutant lines, and indicated that all three receptors are redundantly involved
in the regulation of the steady-state levels of isopentenyladenine- and trans-zeatin-type CKs. By contrast, the levels of cis-zeatin-type CKs were controlled mainly by AHK2 and AHK3. To study the role of CK receptors in the BA-induced PCD pathway,
cultured cells were analysed for their behaviour in the presence of high levels of BA. The results show that CRE1/AHK4, the strongest expressed CK receptor gene of this family in cultured cells, is required for PCD, thus linking this process
to the known CK signalling pathway.

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Available from: Ondrej Novak
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    • "There are CK receptors acting as HK, CK HP and CK RR that create a specific system of reception and transduction of CK signals named multi-step phosphorelay system (Ferreira and Kieber 2005). Some results indicate that one of the A. thaliana CK receptors (AHK4) is engaged in CK-stimulated induction of PCD (Vescovi et al. 2012) This discovery confirmed a central role of AHK4 and excluded participation of two other AHKs named AHK2 and AHK3 in mediating CK (BAP)-induced PCD. Moreover, it has been explained why such a high level of CKs is necessary to induced PCD. "
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