RIKEN Center for Sustainable Resource Science (CSRS), Yokohama, 230-0045, Japan.
Institute of Plant and Microbial Biology, Academia Sinica, Taipei, 11529, Taiwan.
J Exp Bot. 2023 Sep 29;74(18):5870-5880. doi: 10.1093/jxb/erad296.
The unfolded protein response (UPR) is a cellular mechanism that alleviates endoplasmic reticulum stress to maintain protein homeostasis. Although SMALLER TRICHOMES WITH VARIABLE BRANCHES (SVB) is characterized as an emerging UPR factor downstream of the IRE-bZIP60 pathway, whether its homologs participate in the plant UPR remains unknown. Here, we showed that an SVB homolog, SVB-like (SVBL), functions redundantly with SVB in endoplasmic reticulum stress tolerance. The svb-1 svbl-1 double mutant showed a hypersensitivity phenotype and had higher UPR gene expression under endoplasmic reticulum stress than single mutants and the wild type. SVB responded to endoplasmic reticulum stress by accumulating in the root epidermis and phloem cells, but SVBL did not. Ectopic expression of the UPR factor NAC089 up-regulated both SVB and SVBL genes, suggesting that SVB and SVBL work downstream of NAC089. Thus, SVB and SVBL play distinct roles that are modulated by the common upstream regulator NAC089 to cope with endoplasmic reticulum stress in Arabidopsis.
未折叠蛋白反应（UPR）是一种细胞机制，可减轻内质网应激以维持蛋白质的内稳态。虽然 SMALLER TRICHOMES WITH VARIABLE BRANCHES（SVB）被认为是 IRE-bZIP60 途径下游的新兴 UPR 因子，但其同源物是否参与植物 UPR 尚不清楚。在这里，我们表明 SVB 的同源物 SVB-like（SVBL）与 SVB 在内质网应激耐受中具有冗余功能。svb-1 svbl-1 双突变体表现出超敏表型，并且在内质网应激下，其 UPR 基因的表达高于单突变体和野生型。SVB 通过在根表皮和韧皮部细胞中积累来响应内质网应激，但 SVBL 则不会。UPR 因子 NAC089 的异位表达上调了 SVB 和 SVBL 基因，表明 SVB 和 SVBL 在下游作用于 NAC089。因此，SVB 和 SVBL 发挥着不同的作用，这些作用由共同的上游调节因子 NAC089 来调节，以应对拟南芥中的内质网应激。
