The pEXP:CKX2  barley line has been genetically modified by inserting the Arabidopsis thaliana cytokinin dehydrogenase 2 gene under the control of the root-specific promoter derived from the expressed protein gene LOC_Os04g11040.1 of rice

Cytokinin dehydrogenases catalyze the irreversible degradation of cytokinins in a single enzymatic step by oxidative side chain cleavage. Cytokinins, which are chemically N6-substituted purine derivatives, are a class of plant hormones that regulate cell division as well as a large number of developmental events in plants. An important trait regulated by cytokinin is the size of the root system.

A reduced cytokinin status in plants (including barley) causes an enhanced root system which might render plants more tolerant to drought and nutrient deficiencies in the soil. Crop yield is often limited by the availability of water and soil-derived mineral nutrients. A larger root system may enable plants to gain access to more water and nutrients and in this way to cope with adverse environmental conditions.