Abstract
Plants possess a robust and sophisticated innate immune system against pathogens. The intracellular receptors with nucleotide-binding, leucine-rich repeat (NLR) motifs recognize pathogen-derived effector proteins to trigger the immune response. To balance plant growth and rapid pathogen detection, NLR expression is precisely controlled in multifaceted ways. The role of post-transcriptional processing of NLRs, particularly alternative splicing (AS) of introns, in response to infection is recurrently observed but poorly understood. Here we report that the potato NLR gene RB undergoes AS of its intron, resulting in two transcriptional isoforms, which coordinately regulate plant immunity and growth homeostasis. During normal growth, RB predominantly exists as intron-retained isoform RB_IR, encoding a truncated protein containing only the N-terminus of the NLR. Upon late blight infection, the causal pathogen Phytophthora infestans induces intron splicing of RB, increasing the abundance of RB_CDS, which encodes a full-length, and active R protein. By deploying the RB splicing isoforms fused with a luciferase reporter system, we identified IPI-O1 (also known as Avrblb1), the RB cognate effector, as a facilitator of RB AS. Importantly, IPI-O1 directly interacts with potato splicing factor StCWC15 to promote RB splicing for activation of RB-mediated resistance. Thus, our study reveals that StCWC15 serves as a surveillance facilitator sensing the pathogen-secreted effector, and regulates the trade-off between RB- mediated plant immunity and growth, expanding our understanding of molecular plant-microbe interactions.
One-sentence summary Potato resistance gene RB balances plant growth and immunity through AS (alternative splicing), while pathogen-secreted effector IPI-O1 mediates AS of RB by targeting the conserved splicing factor StCWC15, further increasing the RB_CDS expression level to activate immunity.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Revisions to entire manuscript and most figures with additional data.