Science and application of strigolactones

Abstract

Strigolactones (SLs) represent a class of plant hormones that regulate developmental processes and play a role in the response of plants to various biotic and abiotic stresses. Both in planta hormonal roles and ex planta signalling effects of SLs are potentially interesting agricultural targets. In this review, we explore various aspects of SL function and highlight distinct areas of agriculture that may benefit from the use of synthetic SL analogues, and we identify possible bottlenecks. Our objective is to identify where the contributions of science and stakeholders are still needed to achieve harnessing the benefits of SLs for a sustainable agriculture of the near future.

Keywords: agriculture; application; microbiome; stress; strigolactones.

Fig. 1

Strigolactone biosynthesis pathway showing the substrates (in black), proteins (in blue), and genes (in red) encoding the enzymes involved in Arabidopsis (At), rice (Os), pea (Ps), and petunia (Ph) (Flematti et al., 2016). Abscisic acid (ABA) biosynthesis competes with strigolactone biosynthesis for all‐trans‐β‐carotene as substrate.

Fig. 2

Structural variation in natural and synthetic strigolactones (SLs). All these SLs have the conserved D‐ring (see strigol). The canonical SLs have the full ABC‐ring system, as in strigol, orobanchol, 5‐deoxystrigol, and 4‐deoxyorobanchol. The noncanonical SLs have an incomplete ABC‐ring system, as illustrated with zealactone and heliolactone (marked with asterisk). 5‐deoxystrigol and 4‐deoxyorobanchol illustrate the differences in orientation of the BC ring junction. Nijmegen‐1 and GR24 are examples of synthetic SLs. Adapted from Wang & Bouwmeester (2018) and Yoshimura et al. (2019).

Fig. 3

Model of strigolactone (SL) signalling and downstream physiological and phenotypic effects. The dashed arrow indicates the complex inter‐hormonal interactions of SLs. ABA, abscisic acid; CK, cytokinin; ET, ethylene; IAA, auxin; JA, jasmonic acid; SA, salicylic acid.

Fig. 4

Illustration of potential application benefits (solid lines) of strigolactones in agriculture and the factors (broken lines) that are contributing to its potential realization, either positively (←) or negatively (). The colour hues of the panels represent the extent of knowledge and/or application on a field scale and the intensity of effects of the contributing factors (red, negative; green, positive).