Plant TOPLESS-interacting protein effector (Tip)

Plant TOPLESS-interacting protein effectors (Tip effectors) are a diverse class of proteins secreted by biotrophic and hemibiotrophic plant pathogens, including fungi, bacteria, and oomycetes, to facilitate host colonization [1][2]. These effectors target the TOPLESS (TPL) and TOPLESS-RELATED (TPR) family of co-repressors, which act as a central hub for transcriptional repression in plants, integrating signals from hormones such as auxin, jasmonate, and salicylic acid [11][15]. By utilizing conserved interaction motifs, most commonly the Ethylene-responsive element binding factor-associated Amphiphilic Repression (EAR) motif, these effectors competitively bind to the TPL complex [3][12]. This interaction displaces native host repressors, leading to the de-repression of genes that promote pathogen susceptibility and the inhibition of early defense responses like the reactive oxygen species (ROS) burst [8][13]. Prominent examples include the Naked1 (Nkd1) and Tip1-8 effectors from the corn smut fungus Ustilago maydis, which manipulate host auxin and growth signaling to induce gall formation [6][10]. While primarily a focus of agricultural biotechnology rather than human pharmacology, these effectors are high-priority targets for engineering disease-resistant crops [7][14].

Other names

Tip effectorTPL-interacting effectorNaked1 (Nkd1)JA/ET signaling inducible factor 1 (Jsi1)HaRxL21TOPLESS-interacting protein (Tip)TOPLESS-RELATED-interacting effector

Pathogen effectors utilize structural mimicry of host repressor motifs, such as EAR motifs, to competitively bind the plant TOPLESS (TPL) or TOPLESS-RELATED (TPR) co-repressors, thereby displacing native plant transcriptional repressors (e.g., Aux/IAA) and leading to the constitutive activation of susceptibility-promoting and growth-related genes.