The ethylene response factor Pti5 contributes to potato aphid resistance in tomato independent of ethylene signalling.
Bottom Line: These results indicate that Pti5 contributes to basal resistance in susceptible plants and also can synergize with other R gene-mediated defences to limit aphid survival and reproduction.Although Pti5 contains the ERF motif, induction of this gene by aphids was independent of ethylene, since the ACC deaminase (ACD) transgene, which inhibits ethylene synthesis, did not diminish the responsiveness of Pti5 to aphid infestation.These findings suggest that the antixenotic defences that inhibit aphid settling and the antibiotic defences that depress fecundity and promote mortality are regulated through different signalling pathways.
Affiliation: Department of Entomology, University of Arkansas, Fayetteville, AR 72701, USA.Show MeSH
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Mentions: To investigate if Pti5 influenced plant defences against aphids, VIGS was performed to suppress Pti5 expression in the aphid-susceptible tomato ‘Moneymaker’ and the near-isogenic resistant line ‘Motelle’ carrying the Mi-1.2 gene. Plants were infiltrated either with a construct designed to silence Pti5 (TRV-Pti5) or with a control vector of comparable size (TRV-CV). Compared with plants that received the vector control, plants infiltrated with TRV-Pti5 had significantly lower abundance of Pti5 transcripts in the foliage (Fig. 2A; P=0.0013), and the efficacy of silencing was similar in the two genotypes. To measure antibiosis, plants were inoculated with caged adult aphids in a no-choice test, and insect survivorship and reproduction was monitored at 4 and 7 DAI. The aphid-susceptible cultivar ‘MoneyMaker’ had higher numbers of live adults (Fig. 2B; P=0.0098) and offspring (Fig. 2C; P<0.0001) than the aphid-resistant genotype ‘Motelle’ at 4 DAI. Regardless of the genotype tested, plants treated with TRV-Pti5 also supported higher numbers of surviving adults (Fig. 2B; P=0.0033) and live offspring (Fig. 2C; P=0.0063) than the TRV-CV-treated plants. The percentage increase in surviving adults (35% on ‘MoneyMaker’ and 35% on ‘Motelle’) and offspring (37% on ‘MoneyMaker’ and 40% on ‘Motelle’) that resulted from silencing of Pti5 was similar on the two genotypes, and there was no statistically significant interaction between VIGS treatment and plant genotype (P>0.1). This suggested that the effects of silencing by TRV-Pti5 was similar in the two genetic backgrounds. The same patterns of aphid population growth observed at 4- DAI persisted at 7 DAI (Fig. 2D, E), indicating that the effect of Pti5 silencing on aphid population growth remained stable for the time period tested.
Affiliation: Department of Entomology, University of Arkansas, Fayetteville, AR 72701, USA.