Host‐induced silencing of essential genes in Puccinia triticina through transgenic expression of RNAi sequences reduces severity of leaf rust infection in wheat

Abstract

SummaryLeaf rust, caused by the pathogenic fungus Puccinia triticina (Pt), is one of the most serious biotic threats to sustainable wheat production worldwide. This obligate biotrophic pathogen is prevalent worldwide and is known for rapid adaptive evolution to overcome resistant wheat varieties. Novel disease control approaches are therefore required to minimize the yield losses caused by Pt. Having shown previously the potential of host‐delivered RNA interference (HD‐RNAi) in functional screening of Pt genes involved in pathogenesis, we here evaluated the use of this technology in transgenic wheat plants as a method to achieve protection against wheat leaf rust (WLR) infection. Stable expression of hairpin RNAi constructs with sequence homology to Pt MAP‐kinase (PtMAPK1) or a cyclophilin (PtCYC1) encoding gene in susceptible wheat plants showed efficient silencing of the corresponding genes in the interacting fungus resulting in disease resistance throughout the T2 generation. Inhibition of Pt proliferation in transgenic lines by in planta‐induced RNAi was associated with significant reduction in target fungal transcript abundance and reduced fungal biomass accumulation in highly resistant plants. Disease protection was correlated with the presence of siRNA molecules specific to targeted fungal genes in the transgenic lines harbouring the complementary HD‐RNAi construct. This work demonstrates that generating transgenic wheat plants expressing RNAi‐inducing transgenes to silence essential genes in rust fungi can provide effective disease resistance, thus opening an alternative way for developing rust‐resistant crops.

Safe nanotechnologies for increasing the effectiveness of environmentally friendly natural agrochemicals

“…The use of RNAi in pest management has been widely studied in different organisms, showing the potential utility of this technology in both basic and applied science. For instance, expression of transgenes in wheat plants for production of dsRNA targeting fungal genes that code for MAP‐Kinase and cyclophilin caused a pronounced reduction in leaf rust infection by Puccinia triticina . Immunity to Fusarium graminearum was observed in transgenic barley, targeting the sterol 14α‐demethylase (CYP51) genes of the fungus .…”

“…For instance, expression of transgenes in wheat plants for production of dsRNA targeting fungal genes that code for MAP-Kinase and cyclophilin caused a pronounced reduction in leaf rust infection by Puccinia triticina. 100 Immunity to Fusarium graminearum was observed in transgenic barley, targeting the sterol 14 -demethylase (CYP51) genes of the fungus. 101 In addition, when using this RNAi technology to silence a gene critical for survival of an insect pest, resistance of the transgenic plants was observed.…”

Genetic modification to improve disease resistance in crops

“…Similarly, HIGS targeted to a cellulose gene and a highly expressed conserved gene of Bremia lactucae resulted in high levels of resistance to this pathogen in lettuce (Govindarajulu et al, 2015). More often, however, HIGS experiments produce quantitative effects, for example when targeting rust fungi (Panwar et al, 2013(Panwar et al, , 2018Yin & Hulbert, 2018) and virulence factors of V. dahliae in tomato (Song & Thomma, 2018). Overall, HIGS seems to be quite effective against some pathogens (Govindarajulu et al, 2015;Wang et al, 2016) but ineffective against others (Kettles et al, 2018).…”

Host-induced gene silencing involves Arabidopsis ESCRT-III pathway for the transfer of dsRNA-derived siRNA

“…Small (s)RNA effectors play a crucial role in the outcome of plant-pathogen interactions [1][2][3][4] and have a great potential for controlling diseases and pests in crop plants [5][6][7][8] A multitude of transgenic crops expressing dsRNAs targeting essential genes through RNAi are more resistant to viruses [9], viroids [10], bacteria [11], fungi [12][13][14][15], oomycetes [16], nematodes [17,18], and insects [19,20]. Host-induced gene silencing (HIGS) involves i. processing of transgenederived dsRNA into small interfering (si)RNAs, ii.…”