In the model plant Arabidopsis thaliana, the absence of the sole gene copy of CPR5 results in a wide-ranging resistance to viruses, bacteria, and fungi. However, this resistance comes at a cost, as the plants experience severe growth restrictions, spontaneous lesions, and reduced yields. Hence, it became imperative to investigate whether the resistance conferred by the rymv2 gene could be transferred to different rice varieties without adverse consequences.
In Africa, predominant rice varieties, derived from the Asian species Oryza indica, lack the resistance gene. Introducing the gene through conventional means is not a viable option, as the progeny of such “inter-species” hybrids are highly sterile, impeding the easy transmission of resistance traits.
Employing the CRISPR/Cas genome editing technique, the research team demonstrated that mutations in the RYMV2 gene could be induced in an Asian rice variety, rendering it resistant to the virus in a manner similar to the African counterpart. The next phase of the research aims to edit relevant elite African varieties similarly, with the objective of making them accessible to small-scale farmers in Africa. The international research consortium “Healthy Crops,” led by HHU, is dedicated to supporting these farmers.
Plants harbor hereditary mechanisms that were advantageous for survival in early evolutionary stages but have become potentially detrimental. Maize serves as an example, where a gene leads to kernel abortion during drought conditions at fertilization, a trait beneficial to wild perennial ancestors but detrimental to modern agriculture.
The rice under examination shares a similar situation. Professor Frommer notes, “This resistance trait is attributable to the loss of a non-essential gene function. When we completely deactivate the gene, the plants behave normally, but they become resistant to the virus due to the loss of the gene function.”
Dr. Eliza Loo, Group Leader of Healthy Crops, adds, “It is, so to speak, an archetype that was beneficial for its ancestors but now results in devastating crop losses during drought periods. Deactivating this gene seems prudent, and there are no apparent side effects.”
Remarkably, deactivating the closely related CPR5.2 gene or both the RYMV2 and CPR5.2 genes does not lead to impairments, at least under greenhouse conditions. Additionally, the loss of CPR5.2 does not confer RYMV resistance. All indications point to editing the RYMV2 gene as a promising approach to combat rice disease in Africa.
