Strigolactones: New plant hormones in action

Strigolactones: new plant hormones in action

The parasitic weed Striga hermonthica uses strigolactones exuded by the roots of its host, in this case sorghum, as a cue for host presence. The strigolactones induce germination of the seeds of the parasite, which subsequently attaches to the host with a haustorium and robs its host of assimilates, nutrients and water. Photo: Dr Aad van Ast. 

By Cristina Prandi and Hinanit Koltai

Strigolactones were only recently recognized as an important new class of plant hormone, and are now the subject of intensive research. This is leading to rapid growth in our understanding of their diverse roles, as well as novel agricultural applications. The reviews and research in the latest special issue from Journal of Experimental Botany cover a wide range of aspects, from biosynthesis and specificity to the cascade of events leading to perception and transduction, as well as the importance of strigolactone transport and activity in plant development and plant–microbe interactions. The role of the emerging class of non-canonical strigolactones is also covered.

Strigolactones are a class of small terpene-derived molecules that have drawn the attention of the scientific community during the past decade. Although known for decades as germination inducers for the seeds of parasitic plants, in 2005 Akiyama and colleagues reported on their activity as hyphal branching stimulants for arbuscular mycorrhizal fungi, opening new research into the intricate network of communication signals active in the rhizosphere. In 2008 two papers appeared almost simultaneously in Nature (Gomez-Roldan et al., 2008; Umehara et al., 2008) reporting on their role as plant hormones in shoot branching.

Strigolactones are now known unequivocally to play crucial roles both in adaptive changes in plant architecture as a consequence of environmental stimuli and in plant–rhizosphere interactions. They are also recognized as having great potential for agriculture. Such applications include their use in modifying and/or managing root and shoot architecture; as stimulants to induce seed germination of parasitic weeds, controlling infestation by reducing their seed bank; and as ‘biostimulants’ of plant root colonization by arbuscular mycorrhizal fungi, improving plant nutritional capabilities.

Journal of Experimental Botany publishes an exciting mix of research, review and comment on fundamental questions of broad interest in plant science. Regular special issues highlight key areas.