Boyce Thompson Institute for Plant Research, Ithaca, NY 14853, USA.
Plant Pathology and Plant-Microbe Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, NY 14853, USA.
Plant Physiol. 2024 Nov 4;196(3):1997-2013. doi: 10.1093/plphys/kiae401.
Type 2C protein phosphatases (PP2Cs) constitute a large family in most plant species, but relatively few of them have been implicated in immunity. To identify and characterize PP2C phosphatases that affect tomato (Solanum lycopersicum) immunity, we generated loss-of-function mutations in 11 PP2C-encoding genes whose expression is altered in response to immune elicitors or pathogens. We report that 2 closely related PP2C phosphatases, PP2C immunity-associated candidate 3 (Pic3) and Pic12, are involved in regulating resistance to the bacterial pathogen Pseudomonas syringae pv. tomato (Pst). Loss-of-function mutations in Pic3 led to enhanced resistance to Pst in older but not younger leaves, whereas such mutations in Pic12 resulted in enhanced resistance in both older and younger leaves. Overexpression of Pic3 and Pic12 proteins in leaves of Nicotiana benthamiana inhibited resistance to Pst, and this effect was dependent on Pic3/12 phosphatase activity and an N-terminal palmitoylation motif associated with localization to the cell periphery. Pic3, but not Pic12, had a slight negative effect on flagellin-associated reactive oxygen species generation, although their involvement in the response to Pst appeared independent of flagellin. RNA-sequencing analysis of Rio Grande (RG)-PtoR wild-type plants and 2 independent RG-pic3 mutants revealed that the enhanced disease resistance in RG-pic3 older leaves is associated with increased transcript abundance of multiple defense-related genes. RG-pic3/RG-pic12 double-mutant plants exhibited stronger disease resistance than RG-pic3 or RG-pic12 single mutants. Together, our results reveal that Pic3 and Pic12 negatively regulate tomato immunity in an additive manner through flagellin-independent pathways.
2C 型蛋白磷酸酶（PP2Cs）构成了大多数植物物种中的一个大家族，但其中只有少数与免疫有关。为了鉴定和表征影响番茄（Solanum lycopersicum）免疫的 PP2C 磷酸酶，我们针对 11 个 PP2C 编码基因进行了功能丧失突变，这些基因的表达会受到免疫诱导剂或病原体的影响而改变。我们报告称，2 个密切相关的 PP2C 磷酸酶，即 PP2C 免疫相关候选蛋白 3（Pic3）和 Pic12，参与调节对细菌病原体丁香假单胞菌 pv.番茄（Pst）的抗性。Pic3 的功能丧失突变导致较老叶片对 Pst 的抗性增强，但对较年轻叶片无影响，而 Pic12 的功能丧失突变则导致较老和较年轻叶片的抗性增强。Pic3 和 Pic12 蛋白在烟草原生质体叶片中的过表达抑制了对 Pst 的抗性，并且这种效应依赖于 Pic3/12 磷酸酶活性和与定位于细胞边缘相关的 N 端棕榈酰化基序。Pic3 对鞭毛相关活性氧的产生有轻微的负效应，但 Pic3 和 Pic12 对 Pst 的反应似乎不依赖于鞭毛。Rio Grande（RG）-PtoR 野生型植物和 2 个独立的 RG-pic3 突变体的 RNA-seq 分析表明，RG-pic3 较老叶片中增强的抗病性与多个防御相关基因的转录丰度增加有关。RG-pic3/RG-pic12 双突变体植物的抗病性强于 RG-pic3 或 RG-pic12 单突变体。总之，我们的结果表明，Pic3 和 Pic12 通过鞭毛非依赖途径以累加的方式负调控番茄的免疫。
