Biotechnology and Plant Improvement Laboratory, Centre of Biotechnology of Sfax, University of Sfax, Sfax, Tunisia.
Plant Production Department, College of Food and Agricultural Sciences, King Saud University, Riyadh, Saudi Arabia.
PLoS One. 2020 May 19;15(5):e0233420. doi: 10.1371/journal.pone.0233420. eCollection 2020.
Stress-associated proteins (SAPs) are favorable targets to improve stress tolerance in plants, owing to their roles in developmental processes and stress responses. However, the role of SAPs and the molecular mechanisms by which they regulate plant stress responses remain poorly understood. Previously, it was reported that LmSAP expression was upregulated by various abiotic stressors in Lobularia maritima, and that transgenic tobacco lines with constitutively expressed LmSAPΔA20 and LmSAPΔA20-ΔAN1 showed dwarf phenotypes due to the deficiency of cell elongation under salt and osmotic stresses. In this study, we examined the function of A20 domain in the GA pathway in response to abiotic stresses. Transient expression of acGFP-LmSAPΔA20 and acGFP-LmSAPΔA20-ΔAN1 in onion epidermal cells demonstrated that these fused proteins were localized in the nucleo-cytoplasm. However, the truncated form acGFP-LmSAPΔAN1 was localized in the nucleus. Moreover, comparison of native and truncated LmSAP showed dramatic structural changes caused by the deletion of the A20 domain, leading to loss of function and localization. Interestingly, overexpression LmSAP and truncated LmSAPΔAN1 led to up-regulation of GA biosynthetic genes and increased total gibberellins (GAs) content, corresponding with accelerated development in transgenic tobacco plants. Moreover, the dwarf phenotype of the transgenic lines that express LmSAPΔA20 and LmSAPΔA20-ΔAN1 under stress conditions was fully restored by the application of exogenous GA3. These findings improve our understanding of the role of LmSAP in regulating GA homeostasis, which is important for regulating plant development under abiotic stress conditions.
应激相关蛋白（SAPs）是提高植物抗逆性的有利靶标，因为它们在发育过程和应激反应中发挥作用。然而，SAP 的作用以及它们调节植物应激反应的分子机制仍知之甚少。先前有报道称，LmSAP 在 Lobularia maritima 中受到各种非生物胁迫的上调，并且由于盐和渗透胁迫下细胞伸长不足，组成型表达 LmSAPΔA20 和 LmSAPΔA20-ΔAN1 的转基因烟草系表现出矮小表型。在这项研究中，我们研究了 A20 结构域在应对非生物胁迫的 GA 途径中的功能。瞬时表达 acGFP-LmSAPΔA20 和 acGFP-LmSAPΔA20-ΔAN1 在洋葱表皮细胞中表明这些融合蛋白定位于核质。然而，截短形式 acGFP-LmSAPΔAN1 定位于细胞核。此外，比较天然和截短的 LmSAP 表明，由于 A20 结构域的缺失，导致结构发生剧烈变化，从而丧失功能和定位。有趣的是，过量表达 LmSAP 和截短的 LmSAPΔAN1 导致 GA 生物合成基因的上调和总赤霉素（GA）含量的增加，对应于转基因烟草植物的发育加速。此外，在应激条件下表达 LmSAPΔA20 和 LmSAPΔA20-ΔAN1 的转基因系的矮小表型通过外源 GA3 的应用得到完全恢复。这些发现提高了我们对 LmSAP 调节 GA 动态平衡的作用的理解，这对于调节植物在非生物胁迫条件下的发育很重要。
