Strigolactones (SLs) are a class of important plant hormones that play key roles in regulating plant growth and development, stimulating the germination of parasitic Orobanchaceae seeds, and promoting symbiosis with arbuscular mycorrhizal fungi.
Recently, the team led by Jiayang Li and Bing Wang from the Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, conducted a genome-wide association study (GWAS) and identified SlABCG45, a major gene controlling Orobanche parasitism in tomato. SlABCG45 encodes a strigolactone transporter in tomato roots, and precise genome editing of this gene enables a balance between parasitic resistance and plant growth, significantly improving tomato yield under parasitic conditions. This study was published online in The Innovation on January 29, 2025, a prestigious international journal, where Jiupo’s plant growth chamber was cited as the equipment used for seedling cultivation experiments.
Journal:
The Innovation
Impact Factor: 33.2
The research team employed GWAS on a natural tomato population and identified a locus highly associated with Orobanche resistance. The candidate gene within this locus, SlABCG45, encodes an ABC transporter predominantly expressed in the epidermal cells of roots and localized to the plasma membrane, mediating the exudation of strigolactones into the rhizosphere. Genetic analyses further revealed that SlABCG45 and its homolog SlABCG44 play pivotal roles in the exudation of SLs and the stimulation of parasitic seed germination.
Although SLs are plant hormones known to be transported from roots to shoots for long-distance signaling, their transporters have remained largely unidentified. This study demonstrated that SlABCG45 and SlABCG44 jointly contribute to the polar transport of SLs.
Interestingly, SlABCG45 and SlABCG44 exhibit functional divergence. Phosphorus deficiency, a key environmental factor that exacerbates parasitism by promoting SL exudation, dramatically induced SlABCG45 expression by dozens of folds, while only slightly inducing SlABCG44. The transcription factor SlNSP1 was shown to directly bind to the promoters of both SlABCG45 and SlABCG44, playing a critical regulatory role under phosphorus-deficient conditions. Notably, the two transporters differentially affect fruit development: Slabcg45 mutants showed normal fruit development, whereas Slabcg44 mutants produced smaller fruits.
Field trials over two consecutive years under natural conditions in Xinjiang revealed that SlABCG45 knockout mutants exhibited significantly reduced Orobanche infestation (both in terms of parasite numbers and biomass), without compromising fruit size and weight. In fact, these mutants displayed significantly increased fruit numbers and yield per plant. Although knocking out SlCCD8, a key SL biosynthesis gene, also enhanced Orobanche resistance, Slccd8 mutants exhibited severe developmental defects, including dwarfism, excessive branching, reduced fruit size, and significantly lower yield. Small-plot yield data showed that SlABCG45 knockout mutants yielded over 30% more than wild-type controls, highlighting the gene’s potential in breeding Orobanche-resistant tomato cultivars (Figure 1).
Figure 1:Genome editing of SlABCG45 enhances Orobanche resistance and increases tomato yield
In summary, in Orobanche-contaminated fields, wild-type tomatoes synthesize and secrete strigolactones into the rhizosphere, stimulating the germination of various Orobanche species, which then parasitize and severely damage tomato plants, reducing yield. Knocking out SlCCD8 blocks SL biosynthesis, preventing Orobanche seed germination and reducing parasitism, but at the cost of severe growth defects. In contrast, knocking out the SL transporter SlABCG45 does not impair normal fruit development in tomatoes under non-parasitic conditions, while significantly reducing SL exudation into the rhizosphere. This confers broad-spectrum resistance to multiple Orobanche species and leads to a notable yield increase in parasitized fields, achieving a balance between parasitic resistance and fruit yield (Figure 2).
Figure 2:The balance between Orobanche resistance and fruit yield mediated by SlABCG45 in tomato
This study is the first to identify, via GWAS, a major-effect gene controlling Orobanche parasitism in tomato. It elucidates the molecular mechanism underlying SL secretion to the rhizosphere and their upward transport from roots to shoots, as well as the phosphorus-deficiency-induced expression regulation of SL transporters. The research demonstrates that precise manipulation of SlABCG45 via genome editing can simultaneously confer parasite resistance and maintain normal plant development, significantly boosting crop yield in Orobanche-infested fields. This breakthrough fills a key gap in parasitic weed management and provides a sustainable strategy for agriculture.