Dipartimento di Biologia e Biotecnologie Charles Darwin, Sapienza Università di Roma, Rome, Italy.
Instituto de Biologia Molecular y Celular de Plantas, Universidad Politecnica de Valencia-C.S.I.C, Ciudad Politecnica de La Innovacion, Valencia, Spain.
Plant Physiol Biochem. 2023 Aug;201:107865. doi: 10.1016/j.plaphy.2023.107865. Epub 2023 Jul 13.
Plants involve a fine modulation of pectin methylesterase (PME) activity against microbes. PME activity can promote the cell wall stiffening and the production of damage signals able to induce defense responses and plant resistance to pathogens. However, the molecular mechanisms underlying PME activation during disease remain largely unknown. In this study, we explored the role of subtilases (SBTs) as PME activators in Arabidopsis immunity. By using biochemical and reverse genetic approaches, we found that the expression of SBT3.3 and SBT3.5 influences the induction of defense-related PME activity and resistance to the fungus Botrytis cinerea. Arabidopsis sbt3.3 and sbt3.5 knockout mutants showed decreased induction of PME activity and increased susceptibility to the fungus. SBT3.3 expression was stimulated by oligogalacturonides. Overexpression of SBT3.3 overactivated PME activity during fungal infection and enhanced resistance to B. cinerea. A negative correlation was observed between SBT3.3 expression and cell wall methyl ester content in the genotypes analyzed after B. cinerea infection. Increased expression of defense-related genes, including PAD3, CYP81F2 and WAK2, was also revealed in SBT3.3 overexpressing lines. We also demonstrated that SBT3.3 and pro-PME17 are both secreted into the cell wall using distinct protein secretion pathways and different kinetics. Our results propose SBT3.3 and SBT3.5 as modulators of PME activity in Arabidopsis against Botrytis to promptly boost immunity limiting the growth-defense trade-off.
植物通过精细调控果胶甲酯酶（PME）活性来应对微生物。PME 活性可以促进细胞壁变硬，并产生损伤信号，从而诱导防御反应和植物对病原体的抗性。然而，PME 在疾病过程中被激活的分子机制在很大程度上仍然未知。在这项研究中，我们探讨了枯草杆菌蛋白酶（SBTs）作为拟南芥免疫中 PME 激活物的作用。通过生化和反向遗传学方法，我们发现 SBT3.3 和 SBT3.5 的表达影响防御相关 PME 活性的诱导和对真菌灰葡萄孢的抗性。拟南芥 sbt3.3 和 sbt3.5 敲除突变体表现出 PME 活性诱导减少和对真菌的敏感性增加。寡聚半乳糖醛酸刺激 SBT3.3 的表达。在真菌感染期间，过表达 SBT3.3 过度激活 PME 活性并增强对 B. cinerea 的抗性。在 B. cinerea 感染后分析的基因型中，观察到 SBT3.3 表达与细胞壁甲酯含量之间存在负相关。还发现防御相关基因（包括 PAD3、CYP81F2 和 WAK2）的表达增加，这也表明 SBT3.3 过表达系。我们还证明 SBT3.3 和 pro-PME17 都通过不同的蛋白分泌途径和不同的动力学分泌到细胞壁中。我们的结果表明 SBT3.3 和 SBT3.5 是拟南芥针对 Botrytis 的 PME 活性调节剂，可迅速增强免疫，限制生长-防御权衡。
