The plant hormone auxin coordinates wood formation

An international research team investigated the genetic regulation of stem cell division in plant stems. During their investigations, they revealed that the key gene coordinating stem cells, WOX4, is controlled by the vital plant hormone auxin via auxin response proteins. The results are valuable for both fundamental biology and ecology. Since the studied mechanism allows controlling wood formation it could help to solve economic and environmental problems. The research has been published in the journal Nature Communications.

Scientists from the Centre for Organismal Studies (Germany), Gregor Mendel Institute (Austria), Institute of Cytology and Genetics (Russia), Novosibirsk State University (Russia), Wageningen University (Netherlands) and Institute for Plant Molecular and Cellular Biology, Polytechnic University of Valencia (Spain) showed a key role of auxin response regulatory proteins in the cambium (the stem cell niche responsible for wood formation, and also for specified spatial coordination features of gene activity.
Although an influence of auxin on the activity of WOX4 was known before, the exact mechanism was unclear. In this work, the authors demonstrated a direct regulation of WOX4 by auxin signaling factors.

Due to the strong focus on individual cell types, our analysis represents an important milestone for our research on cambium regulation. We more and more understand the exciting complexity of the regulatory network important for a very dynamic growth process which produce a large part of the biomass present on this planet,” said Thomas Greb professor of the Heidelberg University Centre for Organismal Studies and principal investigator of this study.

The amazing cambium and the great auxin

The cambium mediates wood formation which represents a large proportion of terrestrial biomass. The cambium is unique due to producing two different tissues at the same time — xylem also known as wood and phloem — in a bidirectional manner.

The xylem transports water together with dissolved nutrients and the phloem transports sugars essential for growth and development of cells. «Adult» vascular tissues are formed by dead cells and grow constantly in volume due to divisions of stem cells sitting in the cambium. It is important that xylem and phloem are not only produced during the embryonic period but throughout the plant life cycle. When the cambium «dies», so does the stem.

Scientists managed to study wood formation mechanisms in model plant Arabidopsis thaliana, the weed that doesn’t form thick wood itself. Intriguing, but Arabidopsis has all the genetic mechanisms required for wood formation. Thus, all the advantages of the model plant — a small size, a short life cycle and well-annotated genome – are used to investigate the complicated mechanism.

It was shown on Arabidopsis that a small molecule auxin is a King among plant hormones. It’s responsible for a huge amount of different jobs — following the sunlight by plants, responding to gravity, as well as controlling development of all plant organs, including embryos, roots, leaves and stems… Read more on EurekAlert