The plant hormone group, the cytokinins, is implicated in both qualitative and quantitative components of yield. Cytokinins have opposing actions in shoot and root growth-actions shown to involve cytokinin dehydrogenase (CKX), the enzyme that inactivates cytokinin. We revise and provide unambiguous names for the CKX gene family members in wheat, based on the most recently released wheat genome database, IWGSC RefSeq v1.0 & v2.0. We review expression data of CKX gene family members in wheat, revealing tissue-specific gene family member expression as well as sub-genome-specific expression. Manipulation of CKX in cereals shows clear impacts on yield, root growth and orientation, and Zn nutrition, but this also emphasizes the necessity to unlink promotive effects on grain yield from negative effects of cytokinin on root growth and uptake of mineral nutrients, particularly Zn and Fe. Wheat is the most widely grown cereal crop globally, yet is under-research compared with rice and maize. We highlight gaps in our knowledge of the involvement of CKX for wheat. We also highlight the necessity for accurate analysis of endogenous cytokinins, acknowledging why this is challenging, and provide examples where inadequate analyses of endogenous cytokinins have led to unjustified conclusions. We acknowledge that the allohexaploid nature of bread wheat poses challenges in terms of uncovering useful mutations. However, we predict TILLING followed by whole-exome sequencing will uncover informative mutations and we indicate the potential for stacking mutations within the three genomes to modify yield components. We model a wheat ideotype based on CKX manipulation.

中文翻译：

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细胞分裂素脱氢酶：提高小麦产量的遗传靶标。

植物激素类细胞分裂素与产量的定性和定量成分有关。细胞分裂素在芽和根部的生长作用中具有相反的作用，表明其与细胞分裂素脱氢酶（CKX）有关，后者是使细胞分裂素失活的酶。我们基于最新发布的小麦基因组数据库IWGSC RefSeq v1.0和v2.0，对小麦CKX基因家族成员进行修改并提供明确的名称。我们审查了小麦中CKX基因家族成员的表达数据，揭示了组织特异性基因家族成员的表达以及亚基因组特异性表达。谷物中CKX的处理对产量，根系生长和方向以及锌营养具有明显的影响，但这也强调了必须将细胞分裂素对根生长和矿质养分（尤其是锌和铁）的吸收的不利影响与对谷物产量的促进作用脱钩。小麦是全球生长最广泛的谷类作物，但与水稻和玉米相比，尚处于研究阶段。我们强调了我们在CKX参与小麦方面的知识差距。我们还强调了准确分析内源性细胞分裂素的必要性，并认识到为什么这具有挑战性，并举例说明了对内源性细胞分裂素的分析不足导致得出不合理结论的例子。我们承认，在发现有用的突变方面，面包小麦的异源六倍体性质构成了挑战。然而，我们预测TILLING之后再进行全外显子组测序将发现信息性突变，并且我们指出了在三个基因组内堆叠突变以修饰产量组成部分的潜力。我们基于CKX操作对小麦的表型进行建模。