Chinese scientists find key genes to fight against crop parasites

Chinese scientists have identified two key genes responsible for sorghum's resistance to Striga, a parasitic plant that causes significant crop losses. The breakthrough, which also highlights the potential of AI to predict key amino acid sites in strigolactone (SL) transporters, could have wide-ranging applications in enhancing parasitic plant resistance across various crops.

This study, published in Cell, was conducted by Prof. XIE Qi's team at the Institute of Genetics and Developmental Biology of the Chinese Academy of Sciences, in collaboration with five other institutions.

Striga, also known as "witchweed," along with other parasitic plants like Orobanche, relies on host plants for nutrients and water, severely affecting crop yields and agricultural ecosystems. Striga alone infests over 50 million hectares of farmland in Africa, causing annual economic losses of $1.5 billion and affecting over 300 million people. In China, Striga is found in regions such as Guangdong and Yunnan, while Orobanche poses a threat to crops like sunflowers and tomatoes in Inner Mongolia and Xinjiang.

Sorghum is one of the plants susceptible to Striga infestation. Sorghum roots release SLs, a class of plant hormones that help recruit mycorrhizal fungi for nutrient uptake. Unfortunately, Striga seeds dormant in the soil detect these SL signals, which trigger Striga germination and subsequent infestation of the host plant.

In this study, the researchers analyzed transcriptome data from sorghum roots under phosphorus-deficient conditions and strigolactone (SL) treatmen separately. The scientists identified two ABCG family SL transporter genes: Sorghum bicolor SL transporter 1 (SbSLT1) and Sorghum bicolor SL transporter 2 (SbSLT2). They determined that the SbSLT1 and SbSLT2 proteins control the efflux of SLs and knocking out the associated genes inhibits SL secretion. Under these conditions, Striga is unable to germinate and infect the host.

AI-based predictions further identified a conserved phenylalanine residue critical for SL transport. This residue is found not only in sorghum, but also in SL transporters across other monocot crops like maize, rice, and millet, as well as dicotyl crops such as sunflowers and tomatoes, suggesting a conserved mechanism across species. Molecular biology and cellular biology experiments demonstrate the key function of this residue.

Field trials conducted in Striga-prone areas showed that sorghum with knocked-out SbSLT1 and SbSLT2 genes exhibited 67–94% lower infestation rates and 49–52% less yield loss. These findings offer valuable genetic resources and technical support for breeding Striga-resistant sorghum varieties.

The researchers emphasized that the discovery of SbSLT1 and SbSLT2 could provide crucial tools for combating parasitic plants, potentially addressing food security challenges in countries severely affected by parasitic plants, especially African and Asian countries, thereby contributing to regional peace and stability. Future research will focus on validating these genes in crops such as maize, tomato, and millet, with the goal of advancing the commercialization of Striga-resistant crops.

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