Jiayang Shi et al., 2025. Resistance to Striga parasitism through reduction of strigolactone exudation. Cell, 2025, ISSN 0092-8674, https://doi.org/10.1016/j.cell.2025.01.022
Xinwei Ban et al., 2025. Manipulation of a strigolactone transporter in tomato confers resistance to the parasitic weed broomrape. The Innovation, 2025, 100815, ISSN 2666-6758, https://doi.org/10.1016/j.xinn.2025.100815.
At about the same time these two papers show once more that the exudation of strigolactones by host plants is an important factor in the infection process of parasitic plants (Bouwmeester et al., 2021). This has been demonstrated before with mutants and gene editing in the strigolactone biosynthetic pathway (Bari et al., 2019, 2021; Kaniganti et al., 2025; Kohlen et al., 2012; Nicholiaa et al., 2025; Vogel et al., 2010; Zhang et al., 2018). The disadvantage of the latter strategy, however, is the effect it has on shoot branching and other developmental processes. Strigolactone is also a plant hormone that controls shoot branching and root architecture, and disruption of its production not only reduces the concentration of strigolactones in the root exudate but also results in lower endogenous levels of the hormone, with developmental consequences such as increased branching (Kohlen et al., 2012; Vogel et al., 2010; Zhang et al., 2018).
The two papers describe the use of gene editing of the strigolactone transporter to reduce strigolactone exudation and thereby introduce parasitic weed resistance in sorghum and tomato, but with less pleiotropic effects (Jiayang Shi et al, 2025; Xinwei Ban et al., 2025). Also before, others have demonstrated a role for ABC transporters in strigolactone transport, of which the archetype, PDR1, was identified in Petunia (Kretzschmar et al., 2012). Also in that seminal work, a knock-out resulted in lower exudation of strigolactones, and a mild branching phenotype.
Curiously, there is an earlier paper (Bari et al., 2021) reporting gene editing of the same 2 genes in tomato, which also resulted in a mild branching phenotype and resistance against Phelipanche aegyptiaca in a greenhouse experiment. Also in Medicago truncatula, a loss-of-function mutation in ABCG59, a close homologue of Petunia PDR1, resulted in a reduced stimulatory effect on the germination of the parasitic plant Phelipanche ramosa compared to the corresponding wild type (Banasiak et al., 2020). Xinwei Ban et al. (2025) (for tomato) and Jiayang Shi et al. (2025) (for sorghum) now show that the reduced germination through mutations in the strigolactone transporter result in parasitic weed resistance, also under field conditions.
Other authors have already speculated on the identity of strigolactone transporters in monocots, for example in maize (Ravazzolo et al., 2019), but the complexity of expressing these transporter candidates heterologously or create mutants in monocots has so far precluded their unambiguous identification. This makes the study of Jayang Shi et al. the first to characterize monocot strigolactone transporters. This will surely pave the way for more studies in other monocots that severely suffer from parasitic weed infections, especially in the African continent. Strigolactone-based resistance is not uncommon in the African continent, with the lgs1 work of Gebisa Ejeta and coworkers as one of the first (Gobena et al., 2017). Lgs1 is a naturally occurring mutation that results in a change in the strigolactone blend exuded by sorghum and thereby in reduced infection by Striga hermonthica. Interestingly, recently a comparable effect was reported in maize and millet, where mutations in methyl transferases, ZmMET1 and CLAMT1, resulted in a change in the strigolactone blend which also resulted in reduced Striga germination (Li et al., 2023; Kuijer et al., 2024). Interesting is that these mutants do not display pleiotropic developmental effects, likely because the mutations occur beyond the biosynthetic pathway branch towards the hormone strigolactone. Whether the Striga resistance of these mutants, established under greenhouse conditions, holds up in the field remains to be established.
One aspect of the strigolactones is often ignored in these studies aimed at obtaining parasitic weed resistance. In 2005, Akiyama and coworkers showed that the strigolactones exuded by plants into the rhizosphere are host presence signals for AM fungi (Akiyama et al., 2005). The effect of strigolactone knock downs on this symbiosis was occasionally investigated in strigolactone mutants. The M. trunactula mtabcg59 loss-of-function mutant displayed a reduced level of mycorrhization compared to WT (Banasiak et al., 2020). Indeed, Xinwei Ban et al (2025) also show that their transporter mutant displays reduced AM fungi colonization compared with wildtype. Jiayang Shi et al. (2025) speculate about a possible (negative) effect on colonization by AM fungi or other micro-organisms in their transporter mutants but did not investigate that yet. The increasing evidence that strigolactones play a key role in the recruitment of beneficial micro-organisms, AM fungi but also beneficial bacteria (Kim et al., 2022; Schlemper et al., 2017; Abedini et al., 2025) necessitates the critical evaluation of any strigolactone engineering approach to obtain parasitic weed resistance, for any unwanted effects on the rhizosphere microbiome, particularly under conditions of low nutrient (N, P) availability.
See Haustorium 87 for this article and the references