Barley modified for tolerance to drought and nutrient deficiencies

The CKX1:RNAi barley line has been genetically modified by inserting the a copy of the native Hordeum vulgare cytokinin dehydrogenase 1 gene under the control of the constitutive ubiquitin gene promoter from maize.

Cytokinin dehydrogenases catalyze the irreversible degradation of cytokinins in a single enzymatic step by oxidative side chain cleavage. Cytokinins, 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.

Beside the others, cytokinins influence grain filling by regulation of the cell-wall invertase, the important enzyme in a polysacharides metabolism.

Increased cytokinin levels in the grains might enhance the process of grain filling and lead to the production of bigger grains. As the HvCKX1 gene is naturally expressed in the young barley roots and grains, the constitutive expression should not influence the other parts of the plant.

cv. Golden Promise

CKX1:RNAi

The transgenic line showed an up 4-fold lower CKX activity in the barley grains compared to the wild type plants. The total yield from CKX1:RNAi barley was 20% higher than the yield of wild type barley.

The cytokinin dehydrogenase 1 silencing cassette is under the control of the constitutive ubiquitin gene promoter from maize.

The Hygromycin B phosphotransferase selection marker is under the control of the promoter region from Zea mays ubiquitin gene.