Improvement of multiple agronomic traits by a disease resistance gene via cell wall reinforcement

Abstract

The major disease resistance gene Xa4 confers race-specific durable resistance against Xanthomonas oryzae pv. oryzae, which causes the most damaging bacterial disease in rice worldwide. Although Xa4 has been one of the most widely exploited resistance genes in rice production worldwide, its molecular nature remains unknown. Here we show that Xa4, encoding a cell wall-associated kinase, improves multiple traits of agronomic importance without compromising grain yield by strengthening the cell wall via promoting cellulose synthesis and suppressing cell wall loosening. Strengthening of the cell wall by Xa4 enhances resistance to bacterial infection, and also increases mechanical strength of the culm with slightly reduced plant height, which may improve lodging resistance of the rice plant. The simultaneous improvement of multiple agronomic traits conferred by Xa4 may account for its widespread and lasting utilization in rice breeding programmes globally.

Fungal resistance mediated by maize wall‐associated kinase ZmWAK‐RLK1 correlates with reduced benzoxazinoid content

“…ZmWAK-RLK1 can reduce pathogen penetration into host tissues and our transcriptome data revealed different expression levels of several cell wall-related genes, suggesting a positive effect possibly in stabilization of the cell wall. This role has been demonstrated for the rice OsWAK/Xa4 gene conferring quantitative rice blight resistance by strengthening the cell wall (Hu et al, 2017). By contrast, the wheat WAK gene TaWAK/ Snn1 is hijacked by the necrotrophic effector SnTox1 that triggers programmed cell death allowing the pathogen to feed and grow on dead tissue (Shi et al, 2016).…”

“…For instance, in rice > 100 members were found (Zhang et al ., ; Kanneganti & Gupta, ). A number of WAK genes in monocots have been shown to be associated to several functional aspects, such as biotic diseases (Li et al ., ; Hurni et al ., ; Zuo et al ., ; Shi et al ., ; Hu et al ., ), tolerance to phosphorus deficiency (Hufnagel et al ., ), root growth (Kaur et al ., ), as well as gametophyte development (Wang et al ., ). WAKs are the only known proteins that physically link the cell wall to the plasma membrane (Brutus et al ., ; Kohorn & Kohorn, ).…”

“…These signatures can be highly conserved and characteristic for entire pathogen classes as in the case of the bacterial flagellin that is perceived by the leucine-rich repeat receptor kinase (LRR-RK) FLS2, which results in basal and broad-spectrum resistance against most bacteria (Dardick et al, 2012;Macho & Zipfel, 2014). Other receptor kinases only confer resistance to certain races of a particular pathogen (Hu et al, 2017). Receptor kinases have different types of extracellular domains, including leucine-rich repeats, lysine motifs, lectin motifs or epidermal growth factor-like extracellular domains (Gomez-Gomez & Boller, 2000;Dardick et al, 2012;Macho & Zipfel, 2014).…”

“…The WAK genes ZmWAK (qHSR1), ZmWAK-RLK1 (Htn1) and OsWAK (Xa4) confer disease resistance against maize head smut, maize northern corn leaf blight (NCLB) and rice bacterial blight, respectively (Hurni et al, 2015;Zuo et al, 2015;Hu et al, 2017). WAK-mediated resistance involves strengthening of the cell wall intensity by enhancing cellulose biosynthesis and the biosynthesis of phytoalexin (Hu et al, 2017), oxidative burst (Delteil et al, 2016) and defense gene expression (Zuo et al, 2015). Interestingly, there is also one case described where the wheat WAK encoded by the Snn1 gene acts as a susceptibility factor.…”

Processes Underlying a Reproductive Barrier in indica-japonica Rice Hybrids Revealed by Transcriptome Analysis

“…In plants, a well-studied cell wall sensor is AtWAK1, a wall-associated kinase, which resides in the plasma membrane and responds to oligogalacturonides derived from the hydrolysis of cell wall component (Brutus et al, 2010). Xa4, a wall-associated kinase in rice, contributes to disease resistance by strengthening the cell wall via promoting cellulose synthesis and suppressing cell wall loosening (Hu et al, 2017). Unlike wall-associated kinase, no extracellular binding domain or inner kinase domain was found in ORF4+; thus there may exist a coreceptor that interacts with ORF4+ in the plasma membrane and/or a downstream signal protein that interacts with plasma membrane receptor to transmit signals.…”