In the future, agricultural crop production will have to manage with less and less nitrogen fertilisation. The goal must therefore be to increase nitrogen use efficiency so that yield levels can be kept stable. Plants respond to mild nitrogen deficiency by elongating their lateral roots. In this way, more nitrogen can be absorbed than before. Researchers at the IPK Leibniz Institute have now discovered a hormonal regulatory module that mediates the molecular processes of this adaptation. Brassinosteroids and auxins play a central role in this. The results were published in the journal Nature Communications.
It is vital for plants to be able to adapt their root structure to changes in the soil. If there is a slight lack of nitrogen, many plants elongate their lateral roots. The hormone auxin plays an important role in root formation. When nitrogen supply is adequate, enough auxin is transported from the shoot to the roots for them to grow. “However, if there is a moderat lack of nitrogen, shoot-derived auxin is not enough for adaptation, thus local biosynthesis of auxin is strongly enhanced in the root tip,” explains Prof. Dr. Nicolaus von Wirén, head of the Department of Physiology and Cell Biology at the IPK Leibniz Institute.
But it is not only about auxin, brassinosteroids also have an important function in this process. They are synthesised to a greater extent in the event of mild nitrogen deficiency and are passed on as a growth-promoting signal. “This signal in turn is necessary to induce the two genes TAA1 and YUCCA8 in the roots,” explains Dr. Zhongtao Jia, first author of the study. “Thereby, the formation of auxin is controlled and regulated according to the respective nitrogen demand. Ultimately, the elongation of the lateral r