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Isolation of a cytokinin gene, ZOG1 , encoding zeatin O -glucosyltransferase from Phaseolus lunatus

“…Very few genes specific to cytokinins have been isolated although numerous cytokinin-related mutants have been reported (23,24). The ipt (4) gene from Agrobacterium is the most studied gene, relating to cytokinin biosynthesis in microbial systems.…”

Ethylene represses the promoting influence of cytokinin on cell division and expansion of cotyledons in etiolated Arabidopsis thaliana seedlings

“…Antagonism between ethylene and cytokinin, as seen here, is typical of how these hormones govern various developmental processes, including morphogenesis, organ senescence and resistance to pathogens ( Gan & Amasino, 1997 ; Hamant et al, 2002 ; Khaskheli et al, 2018 ; Kučerová et al, 2020 ; Veselova et al, 2021 ). Interestingly, the exception appears to be root and hypocotyl growth, where at least under most conditions the hormones act cooperatively to inhibit expansion ( Deikman, 1997 ; Li et al, 2021 ), apparently because the signal transduction machinery for the two hormones share components ( Liu et al, 2017 ; Zdarska et al, 2019 ; Bidon et al, 2020 ). The current model of signal transduction pathways for each of these hormones begin with two-component regulation; namely, a receptor histidine-kinase coupled to a response regulator ( Liu et al, 2017 ; Bidon et al, 2020 ; Park et al, 2021 ; Wu et al, 2021 ).…”

“…Rather than promoting growth as in the cotyledon, cytokinin usually inhibits growth of both the hypocotyl and root ( Deikman, 1997 ; Li et al, 2021 ). For these inhibitory responses, cytokinin was discovered to act by stimulating the synthesis of the hormone ethylene.…”