Knockdown of strigolactone biosynthesis genes in Populus affects BRANCHED 1 expression and shoot architecture

• Published in: The New phytologist 2016-11, Vol.212 (3), p.613-626
• Main Authors: Muhr, Merlin, Prüfer, Nele, Paulat, Maria, Teichmann, Thomas
• Format: Article
• Language: English
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/nph.14076

Plant architecture is modified by a regulatory system that controls axillary bud outgrowth. Key components in this system are strigolactones (SLs) and BRANCHED 1 , which inhibit bud outgrowth. Their role has been described in herbaceous model systems, including Arabidopsis , rice and pea. However, a role in woody perennial species, including the model tree poplar, has not been unequivocally proven. In this study, we tested a role for SLs in Populus  ×  canescens by treatment with the synthetic SL GR 24. We generated MORE AXILLARY BRANCHING 4 ( MAX 4 ) knockdown lines to study the architectural phenotype of poplar SL biosynthesis mutants and the expression of SL‐regulated genes. We show that GR 24 is perceived by the model tree poplar. MAX 4 knockdown lines exhibit typical SL deficiency symptoms. The observed changes in branching pattern, internode length and plant height can be rescued by grafting. We identified putative poplar BRANCHED 1 and BRANCHED 2 genes and provide evidence for a regulation of BRANCHED 1 by SLs. Our results suggest a conservation of major regulatory mechanisms in bud outgrowth control in the model tree poplar. This may facilitate further research, pinpointing the role of SLs and BRANCHED 1 in the complex regulation of bud outgrowth in trees.