Wheat Argonaute 5 Functions in Aphid–Plant Interaction

Abstract

Aphids feeding on plants experience similar responses to pathogens due to the prolonged and intimate contact with the plant. Diuraphis noxia is an economically important aphid pest on wheat that exhibits such an interaction. Studies on small RNA (sRNA) that regulate genes imparting resistance to wheat against D. noxia have predicted an Argonaute 5 (TaAGO5) gene as possible role player in the resistance response. Functional characterization revealed that TaAGO5 is crucial in regulating the response to infestation by D. noxia. Knockdown of TaAGO5 by 22% in D. noxia resistant wheat resulted in a completely susceptible phenotype. The fecundity and stress levels of D. noxia feeding on these silenced plants were similar to aphids feeding on the susceptible controls. Thus, TaAGO5 is crucial in the defense response by wheat plants during aphid feeding and this is similar to Nicotiana benthaminia plants experiencing arthropod herbivory. Additionally, TaAGO5 was differentially regulated by the Barley mosaic virus (BMV) used in the functional characterization. This provides evidence that TaAGO5 could play a role during virus infection of wheat. The role of AGO5 proteins in plant responses to arthropod herbivory and virus infection is known for dicotyledonous plants. Here, we present data that indicate that this role of TaAGO5 is conserved in wheat and possibly for monocotyledonous plants. These observations extend our knowledge on the roles of AGO proteins in plant resistance.

Bacillus subtilis 26D Triggers Induced Systemic Resistance against Rhopalosiphum padi L. by Regulating the Expression of Genes AGO, DCL and microRNA in Bread Spring Wheat

“…ET and ABA had the strongest effect on the transcription of the AGO5 gene (Table 3). Recently, it was shown that AGO5 has a critical role in regulating the response against colonization by Diuraphis noxia since the knockdown of AGO5 in the resistant wheat line Tugela DN resulted in a fully susceptible phenotype [32].…”

“…sRNAs are generated by DCLs and function through AGOs to silence target genes [21]. The role of AGO1, AGO4, AGO5, DCL2, and DCL4 has been detected in the regulation of defense responses of Arabidopsis, cotton, and wheat against various aphid species [30][31][32][33]. Although the role of miRNAs in plant defense against insects has been established, the mechanisms of action and mechanisms of regulation of RNAi have not been determined.…”

Argonaute5 and its associated small RNAs modulate the transcriptional response during the rhizobia-Phaseolus vulgaris symbiosis

“…AGO5 and, therefore, its cargo sRNAs play different physiological and developmental roles. For instance, AGO5 modulates part of the plant defense responses against the Potato virus X and aphids in A. thaliana and wheat, respectively ( Brosseau and Moffett, 2015 ; Sibisi and Venter, 2020 ). AGO5 also participates in the seed coat pigmentation in G. max ( Cho et al., 2017 ).…”

siRNA Specificity: RNAi Mechanisms and Strategies to Reduce Off-Target Effects

“…Ago4 has been implicated in RNA-directed DNA methylation and chromatin is epigenetically modified by this pathway. Generally, through their small RNA partner, plant Ago proteins are also involved in antiviral or bacterial defense mechanisms as well as responses to herbivore attack ( Pradhan et al, 2017 ; Sibisi and Venter, 2020 ).…”