Nisler Jaroslav
Isotope Laboratory, Institute of Experimental Botany, The Czech Academy of Sciences, Videnska 1083, 142 20 Prague, Czech Republic.
Biochem Soc Trans. 2024 Dec 19;52(6):2297-2306. doi: 10.1042/BST20231561.
Cytokinins are one of the main groups of plant hormones that regulate growth and development of plants. Cytokinin oxidase/dehydrogenase (CKX) is an enzyme that rapidly and irreversibly degrades cytokinins and thus directly affects their concentration and physiological effect. Genetically modified plants with reduced CKX activity in the shoot, i.e. with a higher concentration of cytokinins, showed e.g. increased tolerance to drought stress, formed larger inflorescences and had higher grain yield. For these reasons, chemical compounds capable of inhibiting the CKX activity (CKX inhibitors) were sought. First, they were identified among strong synthetic cytokinins, but their inhibitory activity was low. The trend has been to develop potent CKX inhibitors with minimal intrinsic cytokinin activity in the hope of avoiding the negative effect of cytokinins on root growth. Cloning CKX, production of key recombinant enzymes from Arabidopsis (AtCKX2) and maize (ZmCKX1 and ZmCKX4a), development of screening bioassays and progress in X-ray crystallography and synthetic organic chemistry led to extensive progress in the development of these compounds. Currently, the most suitable CKX inhibitors are seeking their application in research and the commercial sphere in two main areas - plant tissue cultures and agriculture. The key milestones that preceded it are summarized in this review.
细胞分裂素是调节植物生长发育的主要植物激素组分之一。细胞分裂素氧化酶/脱氢酶（CKX）是一种能快速且不可逆地降解细胞分裂素的酶，从而直接影响其浓度和生理效应。在地上部具有降低的CKX活性（即具有较高细胞分裂素浓度）的转基因植物表现出例如对干旱胁迫的耐受性增加、形成更大的花序且具有更高的谷物产量。基于这些原因，人们一直在寻找能够抑制CKX活性的化合物（CKX抑制剂）。最初，它们是在强效合成细胞分裂素中被鉴定出来的，但它们的抑制活性较低。目前的趋势是开发具有最小内在细胞分裂素活性的强效CKX抑制剂，以期避免细胞分裂素对根系生长的负面影响。CKX的克隆、拟南芥（AtCKX2）和玉米（ZmCKX1和ZmCKX4a）关键重组酶的生产、筛选生物测定方法的开发以及X射线晶体学和有机合成化学方面的进展，使得这些化合物的开发取得了广泛进展。目前，最合适的CKX抑制剂正在植物组织培养和农业这两个主要领域寻求在研究和商业领域的应用。本文综述了在此之前的关键里程碑。
