The wheat durable, multipathogen resistance gene Lr34 confers partial blast resistance in rice

Abstract

Summary The wheat gene Lr34 confers durable and partial field resistance against the obligate biotrophic, pathogenic rust fungi and powdery mildew in adult wheat plants. The resistant Lr34 allele evolved after wheat domestication through two gain‐of‐function mutations in an ATP‐binding cassette transporter gene. An Lr34‐like fungal disease resistance with a similar broad‐spectrum specificity and durability has not been described in other cereals. Here, we transformed the resistant Lr34 allele into the japonica rice cultivar Nipponbare. Transgenic rice plants expressing Lr34 showed increased resistance against multiple isolates of the hemibiotrophic pathogen Magnaporthe oryzae, the causal agent of rice blast disease. Host cell invasion during the biotrophic growth phase of rice blast was delayed in Lr34‐expressing rice plants, resulting in smaller necrotic lesions on leaves. Lines with Lr34 also developed a typical, senescence‐based leaf tip necrosis (LTN) phenotype. Development of LTN during early seedling growth had a negative impact on formation of axillary shoots and spikelets in some transgenic lines. One transgenic line developed LTN only at adult plant stage which was correlated with lower Lr34 expression levels at seedling stage. This line showed normal tiller formation and more importantly, disease resistance in this particular line was not compromised. Interestingly, Lr34 in rice is effective against a hemibiotrophic pathogen with a lifestyle and infection strategy that is different from obligate biotrophic rusts and mildew fungi. Lr34 might therefore be used as a source in rice breeding to improve broad‐spectrum disease resistance against the most devastating fungal disease of rice.

Combined GC- and UHPLC-HR-MS Based Metabolomics to Analyze Durable Anti-fungal Resistance Processes in Cereals

“…B) Robust significant differences of different metabolite classes. [4] and a tendency of increase was also reported for wheat. [17] In barley, the metabolic response was different and isocitrate lyase gene expression downregulated.…”

“…Isocitrate concentrations were down-, and succinate concentrations upregulated in high-expressing transgenic Lr34 rice grown under hydroponic conditions, and also gene expression of isocitrate lyase, an enzyme in the glyoxylate cycle, was increased in Lr34 rice. [4] The only robust changes of primary metabolites found in non-infected and infected wheat plants grown in the field were isocitrate and succinate that were increased and decreased, respectively, and a tendency of increase Evaluation of robust significant differences in high Lr34-expressing barley; A) Significant differences between control and Lr34 were evaluated by statistical analysis, and robust differences of both replicate experiments were considered for comparison of growth conditions. B) Robust significant differences of different metabolite classes.…”

“…Lr34 functionality can be transferred to other cereal species like barley, rice and maize, where the gene increased resistance against the adapted pathogens barley leaf rust, barley powdery mildew, [3] rice blast [4] and common maize rust. [5] In contrast to wheat, where Lr34 is only expressed at adult plant stage, barley and rice already showed Lr34 resistance at seedling stage.…”

Arabidopsis ABCG34 contributes to defense against necrotrophic pathogens by mediating the secretion of camalexin

“…Lr34, an ABCG transporter in Triticum aestivum (wheat), is one of the few durable resistance genes that protect the plant from multiple pathogens, namely Puccinia triticina and Puccinia striiformis, which cause leaf rust, and Blumeria graminis, which causes powdery mildew (9). Furthermore, when heterologously expressed in Oryza sativa (rice), Lr34 confers resistance to multiple isolates of Magnaporthe oryzae (10) and therefore is a promising candidate ABC transporter to improve crop plants' resistance to a broad spectrum of pathogens. However, the substrate transported by Lr34 is still unknown.…”

Wheat blast research: Status and imperatives

“…Five major genes for wheat blast resistance viz., Rmg1, Rmg2, Rmg3, Rmg4 and Rmg5 have been reported (Peng et al, 2011). It is interesting however, to note that wheat leaf rust resistance gene Lr34 confers resistance to blast in rice (Krattinger et al, 2016). A word of caution on resistance that even complete resistance Sharma 379 may break down due to nitrogen induced susceptibility (NIS).…”