Zhu Xin, Zhang Kunxi, Gong Peijie, Riemann Michael, Nick Peter
Molecular Cell Biology, Joseph Gottlieb Kölreuter Institute for Plant Sciences, Karlsruhe Institute of Technology, Fritz-Haber-Weg 4, 76131, Karlsruhe, Germany.
College of Horticulture, Henan Agricultural University, Zhengzhou, 450000, Henan, China.
Plant Cell Rep. 2025 Jul 30;44(8):184. doi: 10.1007/s00299-025-03567-x.
Vitis rupestris metacaspase 5, tethered to microtubules, drives grapevine. Hypersensitive response via calcium-dependent auto-processing, linking cytoskeletal dynamics to defence activation by elicitors. Metacaspase 5 is a key player for the hypersensitive response of grapevine against biotrophic pathogens and must be activated rapidly as to prevent colonisation. This activation is likely to occur through changes in protein activity. By expressing a GFP fusion of metacaspase 5 from Vitis rupestris in tobacco BY-2 cells, we can show that this protein is bound to microtubules and that the overexpressors are more responsive to the cell-death-inducing elicitors, cis-3-hexenal and harpin. The disruption of microtubules and actin filaments by these elicitors can be blocked by inhibitors of dynamic turnover and stabilisation. Stabilisation of microtubules by taxol can mitigate cis-3-hexenal induced mortality. Mutations of the catalytic or the putative microtubule-binding sites of metacaspase 5 can suppress auto-processing of this enzyme in biochemical assay. Likewise, the response to cis-3-hexenal (cell death, induction of salicylate-related gene expression) is suppressed in cells, whilst the cytoplasmic remodelling is retained. Calcium and the sites for catalysis or microtubule binding are required for both auto-processing and enzyme activity. We arrive at a model, where metacaspase 5 is inactive when tethered to microtubules, but becomes unleashed for auto-processing upon defence-mediated microtubule breakdown.
栓系于微管的沙地葡萄metacaspase 5驱动葡萄的超敏反应。通过钙依赖性自加工过程，将细胞骨架动力学与激发子介导的防御激活联系起来。Metacaspase 5是葡萄对活体营养型病原体超敏反应的关键因子，必须迅速激活以防止病原体定殖。这种激活可能通过蛋白质活性的变化发生。通过在烟草BY-2细胞中表达沙地葡萄metacaspase 5的绿色荧光蛋白融合体，我们发现该蛋白与微管结合，且过表达株系对诱导细胞死亡的激发子顺式-3-己烯醛和harpin更敏感。这些激发子对微管和肌动蛋白丝的破坏可被动态周转和稳定化抑制剂阻断。紫杉醇对微管的稳定作用可减轻顺式-3-己烯醛诱导的死亡率。在生化分析中，metacaspase 5催化位点或假定的微管结合位点的突变可抑制该酶的自加工过程。同样，在细胞中对顺式-3-己烯醛的反应（细胞死亡、水杨酸相关基因表达的诱导）受到抑制，而细胞质重塑得以保留。自加工过程和酶活性都需要钙以及催化或微管结合位点。我们得出一个模型，即metacaspase 5在栓系于微管时无活性，但在防御介导的微管断裂时被释放以进行自加工。
