A recent study has revealed two innovative genetic mechanisms that contribute to disease resistance in wheat, providing potential strategies to improve resilience against powdery mildew and stripe rust. The research findings were recently published in Nature Genetics, shedding light on the identification of gene pairs responsible for conferring resistance.

Conducted by a team led by Prof. Liu Zhiyong at the Institute of Genetics and Developmental Biology of the Chinese Academy of Science, the studies unveiled that the powdery mildew resistance locus MlIW170 (Pm26) and the stripe rust resistance locus YrTD121, both originating from wild emmer wheat (Triticum dicoccoides), are controlled by pairs of genes encoding nucleotide-binding leucine-rich repeat (NLR) immune receptors.

These gene pairs exhibit a unique architecture in plant immunity, providing new insights into the function and evolution of disease resistance mechanisms in agricultural crops.

Powdery Mildew Resistance Mechanism

The researchers utilized map-based cloning and PacBio HiFi long-read sequencing to pinpoint TdCNL1 and TdCNL5, a genetically linked pair of NLR genes responsible for the resistance conferred by the Pm26 locus. TdCNL1 encodes an NLR protein with a novel potassium-dependent sodium-calcium exchanger (NCKX) integrated domain, while TdCNL5 encodes a canonical coiled-coil NLR (CNL).

Functional experiments, including mutagenesis and gene silencing, confirmed the essential role of both genes in conferring resistance. Transgenic wheat lines expressing both genes or TdCNL1 alone exhibited resistance, while lines expressing only TdCNL5 remained susceptible.

Stripe Rust Resistance Mechanism

In the study on stripe rust resistance, the team identified a head-to-head gene pair, TdNLR1 and TdNLR2, underlying the YrTD121 disease resistance locus. TdNLR1 encodes a canonical NLR protein, while TdNLR2 lacks the typical coiled-coil domain.

Despite structural differences, both genes were found to be crucial for resistance, as evidenced by mutagenesis, gene silencing, CRISPR editing, and transgenic experiments. Notably, neither gene contains integrated effector-recognition domains, indicating a novel NLR configuration.

The findings from wild emmer wheat, the genetic ancestor of modern bread wheat, provide valuable insights into developing high-yielding, disease-resistant wheat varieties through strategic breeding approaches. By crossing wild emmer wheat with high-yielding bread wheat varieties and employing marker-assisted selection, researchers have successfully developed germplasms with enhanced disease resistance.

These discoveries present essential genetic resources for disease resistance and lay the groundwork for breeding wheat varieties that are resistant to multiple diseases.

Source: Phys.org