SUMMARY KNOX (KNOTTED1‐like HOMEOBOX) transcription factors regulate the expression of genes involved in plant growth, development, and immunity by specifically binding to DNA elements. Previously, we found that the Phytophthora infestans RxLR effector Pi22798 targets the potato transcription factor StKNOX3 to promote colonization. We show here that StKNOX3 interacts with StHUB1 and StHUB2, two E3 ubiquitin ligases that monoubiquitinate histone 2B to form H2Bub1. StKNOX3 stabilizes StHUB1 and StHUB2 in the nucleus, and the StKNOX3‐StHUB1/2 complex acts to enhance P. infestans infection. The effector Pi22798 promotes the formation of the StKNOX3‐StHUB1/2 complex, facilitating the nuclear accumulation of StHUB1/2, thereby elevating H2Bub1 levels and increasing plant susceptibility. Combined ChIP‐Seq and RNA‐Seq analyses demonstrate that StKNOX3 modulates transcriptome reprogramming governing cell wall composition, phytohormone responses, and stress responses. StKNOX3 directly binds to the core motifs TGAC or TGTCA in promoter regions of target genes and represses the expression of multiple defense‐related genes. Expression of Pi22798 results in reinforced regulation of the StKNOX3‐targeted genes by affecting the binding affinity of StKNOX3 to their promoters and increasing H2Bub1 levels. Our data support a model in which the host StKNOX3‐StHUB1/2 complex is hijacked by Pi22798 to induce epigenetic modifications that ultimately enhance potato susceptibility to P. infestans.
Jing Zhou, Xiao-Shuang Zhou, Jia-Hui Nie et al.· The Plant Journal· 0 citations
Potato late blight caused by Phytophthora infestans threatens global food security. Unlike the fact that most race-specific resistance to P. infestans (Rpi) genes is rapidly overcome by evolving pathogen populations, the R8 gene from Solanum demissum has conferred durable, quantitative resistance for nearly a century despite encoding a canonical coiled-coil–type nucleotide-binding, leucine-rich repeat (NLR) protein. We identified specific R8 gene analogs that act as negative modulators of R8-mediated immunity. These R8 gene analogs lack independent resistance functions but perturb the recognition of avirulence effector Avr8 by R8 and interfere with oligomerization and plasma membrane association of NRC2, a helper NLR essential for the R8 signaling pathway. Stable overexpression of such RGAs effectively compromises R8-mediated resistance in both potato and Nicotiana benthamiana. We propose that this endogenous regulation balances the intensity of R8-mediated immunity, likely reducing selection pressure on the pathogen population and prolonging resistance durability. Our findings reveal a regulatory layer where genetically linked RGAs control resistance (R) protein–mediated immunity, providing a conceptual framework for durable resistance breeding.
Jia-Hui Nie, Lang Liu, Ye-Tong Qi et al.· Science Advances· 0 citations
A previously unrecognized AAA+ ATPase–F-box module that controls receptor homeostasis is revealed and StGCN4 is identified as a promising molecular target for breeding high-yielding and late blight resistant potato cultivars.
