Sterol-modified plants reduce aphid performance by limiting sterol availability.

Sterols are essential for eukaryotic cell structure and metabolism, yet insects cannot synthesize them de novo and must acquire them through their diet. For insect herbivores, plant-derived sterols are typically converted into cholesterol to support development and reproduction. We previously engineered Arabidopsis thaliana lines with silenced HYD1, resulting in altered sterol composition. In this study, we evaluated the performance of the phloem-feeding aphid Myzus persicae on these sterol-modified plants. Aphids reared on the modified lines (HYD110, 12, 25) exhibited significantly reduced growth, reproduction, and survival compared to those on wild-type Col-0. However, choice assays and electropenetrography (EPG) revealed no differences in host preference or probing and feeding behaviors. Unlike the chewing insect Plutella xylostella, M. persicae did not accumulate atypical sterols but instead showed a significant reduction of total sterol content. Phloem-sap analysis mirrored aphid sterol profiles, lacking the atypical sterols found in leaf tissue of the modified lines. RNA-seq of HYD1 lines revealed no induction of known plant defense pathways; instead, genes involved in translation and nitrate metabolism were upregulated. These findings show that HYD1 silencing reduces host suitability for aphids by limiting sterol availability for insect development and reproduction. Our results highlight the potential of sterol-modified plants as a promising strategy for managing phloem sap-feeding insect pests.