An unreported NB‐LRR protein SUT1 is required for the autoimmune response mediated by type one protein phosphatase 4 mutation (topp4‐1) in Arabidopsis

Abstract

Our previous study indicates that protein phosphatase 1 (PP1) is involved in plant immunity. To elucidate the underlying molecular mechanism, a genetic screening assay was carried out to identify suppressors of type one protein phosphatase 4 mutation (topp4-1) (sut). Molecular and genetic approaches were used to investigate the mechanism of activation of autoimmune response in topp4-1. We performed a map-based cloning assay to identify the SUT1 gene, which encodes a coiled-coil nucleotide-binding leucine-rich-repeat (NB-LRR) protein (CNL). SUT1 physically interacts with TYPE ONE PROTEIN PHOSPHATASE 4 (TOPP4) and topp4-1. The mutated topp4-1 protein activates the autoimmune response in the cytoplasm and promotes the accumulation of SUT1 at both the transcription and the protein levels. Furthermore, our genetic and physical interactions confirm that the topp4-1-induced autoimmune responses are probably mediated by HEAT SHOCK PROTEIN 90 (HSP90) and REQUIRED FOR MLA12 RESISTANCE 1 (RAR1). This study reveals that TOPP4 phosphatase is likely guarded by SUT1 in plant immunity.

Role of Protein Phosphatase1 Regulatory Subunit3 in Mediating the Abscisic Acid Response

“…By the same token, in terms of gene expression and plant morphogenesis, pp1r3 mutants can partially restore the corresponding phenotypes of topp4-1 (Figure 7). Moreover, we have recently reported that the topp4-1 mutant is an autoimmune activated mutant with high expression of many immune-related genes (Yan et al, 2019;Liu et al, 2020). In pp1r3-2 topp4-1, the large number of highly expressed DEGs related to plant immunity in topp4-1 was partially restored by pp1r3-2 (Supplemental Figure S4E).…”

“…Many studies report that transcription factors downstream of ABA can regulate ABA synthesis and signal transduction through a regulatory feedback loop (Zong et al, 2016;Tan et al, 2018;Wang et al, 2019). For example, ABFs activated by ABA promote the expression of the ABA co-receptor genes ABI1 and ABI2, which in turn inhibit ABA signaling through dephosphorylation of ABFs (Wang et al, 2019).…”

“…The process of affinity purification of GFP fusion protein by anti-GFP antibody was based on previously published paper (Yan et al, 2019). 3-week-old GFP or TOPP4-GFP transgenic plants were used.…”

“…Previously, we identified and used a dominant-negative mutant of TOPP4, topp4-1, to show that TOPP4 participates in DELLA-mediated gibberellic acid (GA) signaling, Pin-Formed (PIN1)-mediated pavement cell morphogenesis, and Phytochrome Interacting Factor 5 (PIF5)-regulated light morphogenesis by dephosphorylating different substrates (Qin et al, 2014;Guo et al, 2015;Yue et al, 2016). Recently, we found TOPPs interact with Suppressor of topp4-1 (SUT1), a CC (coiled-coil)-NBS (nucleotide-binding site)-LRR (Leu-rich-repeat) resistance protein that contributes to plant immunity (Yan et al, 2019;Liu et al, 2020). However, detailed investigation reveals that understanding TOPPs and their substrate relationships does not fully explain how TOPPs regulate specific cell processes.…”

Diversity, structure and function of the coiled‐coil domains of plant NLR immune receptors

“…Similar to its non‐orthologous RPM1 in Arabidopsis , soybean RPG1‐B (for resistance to Pseudomonas syringae pv glycinea ) confers species‐specific resistance to P. syringae expressing AvrB; the RPG1‐B CC domain interacts with RIN4‐like proteins from soybean (Selote and Kachroo, 2010). In Arabidopsis , SUPPRESSORS OF TOPP4‐1, 1 (SUT1), is speculated to guard TYPE ONE PROTEIN PHOSPHATASE 4 (TOPP4) for plant immunity via TOPP4 /SUT1‐CC interaction (Yan et al, 2019).…”