Abstract
Cytokinins induce growth and greening of calli in the presence of auxin. We have previously isolated cytokinin-hypersensitive mutants of Arabidopsis, ckh1 and ckh2, which can respond to lower levels of cytokinins to produce green and rapidly growing calli. Positional cloning of the CKH2 gene revealed that it was identical with PICKLE and encodes a CHD3 class protein of the SWI2/SNF2 family. In animals, this class of proteins are a part of a chromatin remodeling and histone deacetylation complex. The PICKLE gene has been reported to be required for transition from embryonic to post-embryonic phase. We speculate that this process might be regulated by cytokinins. Double mutants of ckh2 and cre1 (a cytokinin receptor mutant) exhibited additive phenotypes, suggesting that CKH2 is not downstream of cytokinin receptors but modulate cytokinin signaling pathway.
