Identification and characterization of wheat stem rust resistance gene Sr21 effective against the Ug99 race group at high temperature

Abstract

Wheat stem rust, caused by Puccinia graminis f. sp. tritici (Pgt), is a devastating foliar disease. The Ug99 race group has combined virulence to most stem rust (Sr) resistance genes deployed in wheat and is a threat to global wheat production. Here we identified a coiled-coil, nucleotide-binding leucine-rich repeat protein (NLR) completely linked to the Ug99 resistance gene Sr21 from Triticum monococcum. Loss-of-function mutations and transgenic complementation confirmed that this gene is Sr21. Sr21 transcripts were significantly higher at high temperatures, and this was associated with significant upregulation of pathogenesis related (PR) genes and increased levels of resistance at those temperatures. Introgression of Sr21 into hexaploid wheat resulted in lower levels of resistance than in diploid wheat, but transgenic hexaploid wheat lines with high levels of Sr21 expression showed high levels of resistance. Sr21 can be a valuable component of transgenic cassettes or gene pyramids combining multiple resistance genes against Ug99.

Genetic strategies for improving crop yields

“…Moreover, surface-and intracellular-immunity systems appear to respond differently to changes in temperature, owing to effects on the microorganisms and hosts that are not completely understood 42,43 . Although immunity mediated by intracellular receptors tends to be less efficient as temperatures increase, some resistance genes confer protection at higher temperatures 44,45 . Although these findings are reassuring, they highlight the need for more genotype × environment studies in crops to stabilize resistance in increasingly precarious climates.…”

Mapping QTL for Resistance to New Virulent Races of Wheat Stripe Rust from Two Argentinean Wheat Cultivars

“…These proteins recognize pathogen effectors (or the modified host proteins) and trigger either hypersensitive reactions (Periyannan et al, 2013;Saintenac et al, 2013;Mago et al, 2015;Steuernagel et al, 2016;Marchal et al, 2018) or the coordinated upregulation of Pathogenesis-related (PR) genes that reduce pathogen growth Chen et al, 2018). All-stage resistance genes (also called major or seedling resistance genes) are effective starting at early stages of plant development and typically encode nucleotide binding site-leucine-rich repeat (NBS-LRR) resistance proteins.…”

“…All-stage resistance genes (also called major or seedling resistance genes) are effective starting at early stages of plant development and typically encode nucleotide binding site-leucine-rich repeat (NBS-LRR) resistance proteins. These proteins recognize pathogen effectors (or the modified host proteins) and trigger either hypersensitive reactions (Periyannan et al, 2013;Saintenac et al, 2013;Mago et al, 2015;Steuernagel et al, 2016;Marchal et al, 2018) or the coordinated upregulation of Pathogenesis-related (PR) genes that reduce pathogen growth Chen et al, 2018). By contrast, the few wheat rust APR resistance genes cloned so far encode a more diverse set of proteins than the NBS-LRR, which include an ATP-binding cassette (ABC) transporter (Krattinger et al, 2009), a kinase-START lipid binding protein (Fu et al, 2009;Gou et al, 2015), and a hexose transporter (Moore et al, 2015).…”

The wheatSr22,Sr33,Sr35andSr45genes confer resistance against stem rust in barley

“…Nine major, dominant Sr genes have been cloned so far from wheat or its wild progenitors; these being Sr13 from durum wheat (T. turgidum ssp. durum) (Zhang et al, 2017), Sr21, Sr22 and Sr35 from T. boeoticum and T. monococcum (Saintenac et al, 2013;Steuernagel et al, 2016, Chen et al, 2018, Sr33, Sr45, Sr46, and SrTA1662 from Aegilops tauschii (Periyannan et al, 2013;Steuernagel et al, 2016;Arora et al, 2018), and Sr50 from rye (Secale cereale) (Mago et al, 2015) (Figure 1b). All these genes encode coiled-coil (CC)-NLR proteins and confer resistance to the Ug99 race group.…”