The Expression of Cytoplasmic Effectors by Phytophthora infestans in Potato Leaves and Tubers Is Organ-Biased

Abstract

Potato late blight is a devastating disease caused by Phytophthora infestans that affects organs, such as leaves and tubers. Previous studies of organ specificity in this interaction have mainly addressed the plant side (i.e., screening for resistance to late blight in potato leaves versus tubers). However, the extent of the organ specificity of P. infestans virulence mechanisms remains understudied. Here, we investigated the extent of organ-specific expression of effector genes using RNA-seq by contrasting the infection of leaves and tubers of potato (cultivar Russet Burbank) by the P. infestans strain 1306. We focused on RxLR and Crinkler (CRN) effectors to obtain insight on genes putatively involved in P. infestans virulence exhibiting differential expression during leaf versus tuber infection. Our results indicated that (i) the proportion of differentially expressed genes (DEGs) increased over time; (ii) a high proportion of effector genes was differentially expressed at one or more time points (34% of RxLRs and 58% of CRNs); and (iii) some RxLR and CRN families appeared to host more DEGs than others. Quantitative reverse transcription PCR (RT-qPCR) was also used to assess the expression of seven RxLR effectors in a time-course experiment, allowing us to validate their organ-biased profiles. Organ-specific effector genes may perform distinct virulence roles at the organ level, which should be considered when performing effectoromics or any infection study. These results bring new insights into the organ specificity of the potato- P. infestans interaction that could lead to improved potato-breeding programs using effectoromics-based approaches. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .