Summary Plant recognition of pathogen-associated molecular patterns (PAMPs) such as bacterial flagellin-derived flg22 triggers rapid activation of mitogen-activated protein kinases (MAPKs) and generation of reactive oxygen species (ROS). Arabidopsis has at least four PAMP/pathogen-responsive MAPKs: MPK3, MPK6, MPK4, and MPK11. It was speculated that these MAPKs may function downstream of ROS in plant immunity because of their activation by exogenously added H2O2. MPK3/MPK6 or their orthologs in other plant species were also reported to be involved in ROS burst from the plant respiratory burst oxidase homologue (Rboh) of human neutrophil gp91phox. However, detailed genetic analysis is lacking. Using a chemical genetic approach, we generated another conditional loss-of-function mpk3 mpk6 double mutant. Together with the conditionally rescued mpk3 mpk6 double mutant reported previously, we demonstrate that flg22-triggered ROS burst is independent of MPK3/MPK6. In Arabidopsis mutant lacking a functional AtRbohD, flg22-induced ROS burst was completely blocked. However, the activation of MPK3/MPK6 was not affected. Based on these results, we conclude that the rapid ROS burst and MPK3/MPK6 activation are two independent early signaling events downstream of FLS2 in plant immunity. We also found that MPK4 negatively impacts the flg22-induced ROS burst. In addition, salicylic acid-pretreatment enhances AtRbohD-mediated ROS burst, which is again independent of MPK3/MPK6 based on the analysis of mpk3 mpk6 double mutant. The establishment of a mpk3 mpk6 double mutant system using the chemical genetic approach offers us a powerful tool to investigate the function of MPK3/MPK6 in plant defense signaling pathway.

The jasmonic acid (JA) pathway plays a key role in plant defense responses against herbivorous insects. CORONATINE INSENSITIVE1 (COI1) is an F-box protein essential for all jasmonate responses. However, the precise defense function of COI1 in monocotyledonous plants, especially in rice (Oryza sativa L.) is largely unknown. We silenced OsCOI1 in rice plants via RNA interference (RNAi) to determine the role of OsCOI1 in rice defense against rice leaf folder (LF) Cnaphalocrocis medinalis, a chewing insect, and brown planthopper (BPH) Nilaparvata lugens, a phloem-feeding insect. In wild-type rice plants (WT), the transcripts of OsCOI1 were strongly and continuously up-regulated by LF infestation and methyl jasmonate (MeJA) treatment, but not by BPH infestation. The abundance of trypsin protease inhibitor (TrypPI), and the enzymatic activities of polyphenol oxidase (PPO) and peroxidase (POD) were enhanced in response to both LF and BPH infestation, but the activity of lipoxygenase (LOX) was only induced by LF. The RNAi lines with repressed expression of OsCOI1 showed reduced resistance against LF, but no change against BPH. Silencing OsCOI1 did not alter LF-induced LOX activity and JA content, but it led to a reduction in the TrypPI content, POD and PPO activity by 62.3%, 48.5% and 27.2%, respectively. In addition, MeJA-induced TrypPI and POD activity were reduced by 57.2% and 48.2% in OsCOI1 RNAi plants. These results suggest that OsCOI1 is an indispensable signaling component, controlling JA-regulated defense against chewing insect (LF) in rice plants, and COI1 is also required for induction of TrypPI, POD and PPO in rice defense response to LF infestation.

AimsTo assess the safety and efficacy of parenchymal‐sparing hepatectomy (PSH) as a treatment of colorectal liver metastases (CLM).MethodsA comprehensive medical literature search was performed. Perioperative and long‐term survival outcomes were pooled. Subgroup analysis and meta‐regression analysis were performed to identify potential sources of heterogeneity.ResultsA total of 18 studies comprising 7081 CLM patients were eligible for this study. The PSH was performed on 3974 (56.1%) patients. We found that the OS (overall survival; hazard ratio [HR] = 1.01, 95% confidence interval [CI]: 0.94‐1.08) and RFS (recurrence‐free survival; HR = 1.00, 95% CI: 0.94‐1.07) were comparable between non‐PSH and PSH group. The perioperative outcomes were better in PSH than in non‐PSH group. Non‐PSH group was significantly associated with longer operative time (standard mean difference [SMD] = 1.17, 95% CI: 0.33‐2.00), increased estimated blood loss (SMD = 1.36, 95% CI: 0.64‐2.07), higher intraoperative transfusion rate (risk ratio [RR] = 2.27, 95% CI: 1.60‐3.23), and more postoperative complications (RR = 1.39, 95% CI: 1.16‐1.66). Meta‐regression analyses revealed that no variable influenced the association between surgical types and the survival outcomes.ConclusionsThis study shows that PSH is associated with better perioperative outcomes without compromising oncological outcomes. Given the increasing incidence of hepatic parenchyma, the PSH treatment offers a greater opportunity of repeat resection for intrahepatic recurrent tumors. It should be considered as an effective surgical approach for CLM.

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