Ralstonia solanacearum Type III Effectors with Predicted Nuclear Localization Signal Localize to Various Cell Compartments and Modulate Immune Responses in Nicotiana spp.

Abstract

<i>Ralstonia solanacearum</i> (<i>Rso</i>) is a causal agent of bacterial wilt in <i>Solanaceae</i> crops worldwide including Republic of Korea. <i>Rso</i> virulence predominantly relies on type III secreted effectors (T3Es). However, only a handful of <i>Rso</i> T3Es have been characterized. In this study, we investigated subcellular localization of and manipulation of plant immunity by 8 <i>Rso</i> T3Es predicted to harbor a nuclear localization signal (NLS). While 2 of these T3Es elicited cell death in both <i>Nicotiana benthamiana</i> and <i>N. tabacum</i>, only one was dependent on suppressor of G2 allele of skp1 (SGT1), a molecular chaperone of nucleotide-binding and leucine-rich repeat immune receptors. We also identified T3Es that differentially regulate flg22-induced reactive oxygen species production and gene expression. Interestingly, several of the NLS-containing T3Es translationally fused with yellow fluorescent protein accumulated in subcellular compartments other than the cell nucleus. Our findings bring new clues to decipher <i>Rso</i> T3E function <i>in planta</i>.