Developing Striga resistance in sorghum by modulating host cues through CRISPR/Cas9 gene editing

Area of Science:

• Agricultural Biotechnology
• Plant Genetics
• Crop Improvement

Background:

• Sorghum (Sorghum bicolor L.) is a vital food staple in Sub-Saharan Africa, severely impacted by the parasitic weed Striga.
• Striga causes substantial yield losses, affecting over 60% of farmlands and threatening food security.
• Strigolactones (SLs) are plant hormones involved in plant development and host-parasite interactions, including Striga germination.

Purpose of the Study:

• To develop durable Striga resistance in sorghum by utilizing CRISPR/Cas9 technology.
• To induce targeted mutations in key strigolactone biosynthetic genes (CCD7, CCD8, MAX1, and DUF) in sorghum.
• To investigate the functional roles of these genes in SL production and Striga resistance.

Main Methods:

• CRISPR/Cas9 gene editing was employed to introduce mutations in CCD7, CCD8, MAX1, and DUF genes in two sorghum cultivars.
• Agrobacterium-mediated transformation of immature sorghum embryos was used to deliver the editing constructs.
• Analysis included transformation and gene editing efficiency assessment, molecular characterization of mutations, gene expression analysis, phenotypic evaluation, root exudate analysis, and Striga infection assays.

Main Results:

• High transformation (~70%) and gene editing efficiencies (up to 17.5%) were achieved in the selected sorghum genotypes.
• Homozygous loss-of-function mutations were confirmed in the targeted genes, leading to reduced expression of SL biosynthetic pathway genes.
• Edited sorghum lines exhibited significantly reduced SL production in root exudates and showed delayed or reduced Striga emergence rates.

Conclusions:

• CRISPR/Cas9-mediated gene editing effectively created transgene-free, Striga-resistant sorghum plants with precise mutations.
• Altering SL production through targeted gene editing is a viable strategy for developing durable resistance against Striga infestations.
• This study provides valuable insights into the function of specific genes in sorghum's SL pathway and offers a promising tool for crop improvement in Striga-prone regions.