New insights into regulation of root initiation

When young, dark-grown seedlings of thale cress are given light, they start to form roots from the stem-like part of the plant called the hypocotyl. Abdellah Lakehal used this system to study how the initiation of these adventitious roots is regulated at the molecular level. Abdellah Lakehal successfully defended his Ph.D. thesis on Thursday, 28th of November 2019 at Umeå University.

Plant hormones are growth regulators that play an important role in adventitious root initiation. The plant hormones auxin, jasmonate and cytokinin interact with each other to control adventitious root initiation. While auxin promotes adventitious root formation, jasmonate and cytokinins inhibit this process. Abdellah Lakehal now added several new molecular pieces to this complex regulation.

He identified two so-called auxin co-receptors, proteins that fine-tune the auxin response during adventitious root initiation. He also showed how jasmonate controls the degradation of auxin in a feedback manner by regulating the expression of another protein. Abdellah Lakehal concluded that this protein mediates a molecular circuit that stabilizes the interaction between auxin and jasmonate. In addition, he identified additional components from the jasmonate pathway that prevent the formation of adventitious roots by regulating cytokinin signaling.

Abdellah Lakehal worked with thale cress seedlings. To induce the formation of adventitious roots, he first let the seedlings grow in darkness for three days. Then the dark-grown seedlings were exposed to light to trigger the development of adventitious roots on the hypocotyl, which is an embryonic stem.

Adventitious roots are important for the vegetative propagation of plants. Many plant species naturally form adventitious roots, including grasses, cereals, bulb plants, blackberries and strawberries to propagate without setting seeds. But adventitious roots can also be induced by wounding, flooding or changes in temperature. The vegetative propagation of plants is widely used in forestry and agriculture for clonally multiplying elite genotypes.