New insights into tree architecture: researchers shed light on bushy birch variants

Research carried out at the University of Helsinki provides new insights into understanding the genetic structure of birch trees, especially bushy growth forms. The findings can be applied, for example, in the fields of plant breeding and biodiversity.

Trees are nature’s plant giants. Their growth patterns and structures vary widely across species and environments. In general, a tree is a tall and perennial woody plant with a clearly defined main stem. In contrast, a bush is another form of woody plant, characterized as being shorter, perennial, and without an evident main stem.

A team of researchers from the University of Helsinki and Natural Resources Institute Finland has made notable advancements in understanding the genetic structure of birch trees, contributing significant knowledge to the field of plant genetics. Their study, recently published in Proceedings of the National Academy of Sciences (PNAS) journal, explores the intriguing world of birch tree architecture.

The discovery of the kanttarelli mutant

The research focused on identifying and understanding variants of birch trees that exhibit bushy growth forms. Among these, a mutant named 'kanttarelli' stands out, alongside variants like 'Luutakoivu,' 'Pöytäkoivu,' and 'Luuta E8032.' These birches display unique structural characteristics, diverging from the typical growth patterns of birch trees. The team's investigation pinpointed an early stop codon in the BpMAX1 gene in the kanttarelli mutant, essential for the synthesis of strigolactones, which is important for plant growth and development. The kanttarelli mutant and phenocopying transgenic BpMAX1-RNAi lines had increased numbers of high-order branches.

Intriguingly, the auxin concentration formed a gradient along the main stem in the wild type, with more auxin in the uppermost internodes and less toward the base, whereas this gradient was absent in the transgenic line. Mathematical modelling showed that this difference in auxin distribution may result from the differing architectures.

Implications for plant breeding and biodiversity

The findings of this study have significant implications for plant breeding. By understanding the genetic underpinnings of tree architecture, breeders could develop birch varieties with desired traits strategically for various purposes.

“For example, bushy trees might be preferred for urban or ornamental uses, while variants of certain branching patterns could be more efficient for the timber or pulping industries. Additionally, this research sheds light on the role of strigolactones in birch branching development, opening the possibility for cultivating log trees with straighter trunks and fewer branches, an invaluable trait for lumber production”, says Su Chang, a PhD student from Ykä Helariutta’s research group.

The study also contributes to biodiversity and offers genetic resources for future breeding efforts.

Original article

Tree architecture: A strigolactone-deficient mutant reveals a connection between branching order and auxin gradient along the tree stem

Contact information

Chang Su, Doctoral Researcher,, 029 415 9422