Rytz Thérèse C, Feng Juanjuan, Barros Jessica A S, Vierstra Richard D
Department of Biology Washington University in St. Louis St. Louis Missouri USA.
Benson Hill Inc. St. Louis Missouri USA.
Plant Direct. 2023 Jul 16;7(7):e506. doi: 10.1002/pld3.506. eCollection 2023 Jul.
The reversible conjugation of small ubiquitin-like modifier (SUMO) to other proteins has pervasive roles in various aspects of plant development and stress defense through its selective attachment to numerous intracellular substrates. An intriguing aspect of SUMO is that it can be further modified by SUMOylation and ubiquitylation, which isopeptide-link either or both polypeptides to internal lysines within previously bound SUMOs. Although detectable by mass spectrometry, the functions of these secondary modifications remain obscure. Here, we generated transgenic that replaced the two related and essential SUMO isoforms (SUMO1 and SUMO2) with a lysine-null SUMO1 variant (K0) immune to further SUMOylation/ubiquitylation at these residues. Remarkably, homozygous plants developed normally, were not hypersensitive to heat stress, and have nearly unaltered SUMOylation profiles during heat shock. However, subtle changes in tolerance to salt, paraquat, and the DNA-damaging agents bleomycin and methane methylsulfonate were evident, as were increased sensitivities to ABA and the gibberellic acid biosynthesis inhibitor paclobutrazol, suggesting roles for these secondary modifications in stress defense, DNA repair, and hormone signaling. We also generated viable lines expressing a SUMO1(K0) variant specifically designed to help isolate SUMO conjugates and map SUMOylation sites, thus offering a new tool for investigating SUMO .
小泛素样修饰物（SUMO）与其他蛋白质的可逆共轭作用，通过其选择性地附着于众多细胞内底物，在植物发育和应激防御的各个方面发挥着广泛作用。SUMO一个有趣的方面是，它可以被SUMO化和泛素化进一步修饰，这两种异肽连接方式可将一种或两种多肽连接到先前结合的SUMO内部的赖氨酸上。尽管可通过质谱检测到，但这些二级修饰的功能仍不清楚。在这里，我们生成了转基因植物，用一种赖氨酸缺失的SUMO1变体（K0）取代了两种相关且必需的SUMO亚型（SUMO1和SUMO2），该变体在这些残基处对进一步的SUMO化/泛素化免疫。值得注意的是，纯合转基因植物正常发育，对热胁迫不敏感，并且在热激期间SUMO化谱几乎没有改变。然而，对盐、百草枯以及DNA损伤剂博来霉素和甲磺酸甲酯的耐受性有细微变化，对脱落酸和赤霉素生物合成抑制剂多效唑的敏感性也增加，这表明这些二级修饰在应激防御、DNA修复和激素信号传导中发挥作用。我们还生成了表达SUMO1（K0）变体的有活力的转基因株系，该变体专门设计用于帮助分离SUMO共轭物并定位SUMO化位点，从而为研究SUMO提供了一种新工具。
