Stavridou Evangelia, Michailidis Michail, Gedeon Stella, Ioakeim Antri, Kostas Stefanos, Chronopoulou Evangelia, Labrou Nikolaos E, Edwards Robert, Day Anil, Nianiou-Obeidat Irini, Madesis Panagiotis
Institute of Applied Biosciences, Centre for Research & Technology Hellas, Thessaloniki, Greece.
Laboratory of Pomology, Department of Horticulture, School of Agriculture, Aristotle University of Thessaloniki, Thessaloniki, Greece.
Front Plant Sci. 2019 Jan 11;9:1861. doi: 10.3389/fpls.2018.01861. eCollection 2018.
Chloroplasts are organelles subjected to extreme oxidative stress conditions. Biomolecules produced in the chloroplasts act as signals guiding plant metabolism toward stress tolerance and play a major role in regulating gene expression in the nucleus. Herein, we used transplastomic plants as an alternative approach to expression of transgenes in the nucleus for conferring stress tolerance to abiotic stresses and herbicides. To investigate the morphophysiological and molecular mechanisms and the role of plastid expressed GSTs in tobacco stress detoxification and stress tolerance, we used transplastomic tobacco lines overexpressing a theta class (GST) in chloroplasts. The transplastomic plants were tested under drought (0, 100, and 200 mM mannitol) and salinity (0, 150, and 300 mM NaCl) , and under herbicide stress (Diquat). Our results suggest that pt lines were tolerant to herbicide-induced oxidative and salinity stresses and showed enhanced response tolerance to mannitol-induced osmotic stress compared to WT plants. Overexpression of the GSTT in the chloroplasts resulted in enhanced photo-tolerance and turgor maintenance under stress. Whole-genome transcriptome analysis revealed that genes related to stress tolerance, were upregulated in pt 2a line under both control and high mannitol stress conditions. Transplastomic plants overexpressing the pt 2a in the chloroplast showed a state of acclimation to stress, as only limited number of genes were upregulated in the pt 2a transplastomic line compared to WT under stress conditions while at the same time genes related to stress tolerance were upregulated in pt 2a plants compared to WT in stress-free conditions. In parallel, the metabolic profile indicated limited perturbations of the metabolic homeostasis in the transplastomic lines and greater accumulation of mannitol, and soluble sugars under high mannitol stress. Therefore, transplastomic lines seem to be in a state of acclimation to stress under stress-free conditions, which was maintained even under high mannitol stress. The results help to elucidate the role of GSTs in plant abiotic stress tolerance and the underlying mechanisms of the GSTs expressed in the chloroplast, toward environmental resilience of cultivated crops.
叶绿体是遭受极端氧化应激条件的细胞器。叶绿体中产生的生物分子作为引导植物代谢走向胁迫耐受性的信号，并在调节细胞核中的基因表达中起主要作用。在此，我们使用转质体植物作为在细胞核中表达转基因的替代方法，以赋予对非生物胁迫和除草剂的耐受性。为了研究形态生理和分子机制以及质体表达的谷胱甘肽S-转移酶（GSTs）在烟草胁迫解毒和胁迫耐受性中的作用，我们使用了在叶绿体中过表达θ类（GST）的转质体烟草品系。对转质体植物在干旱（0、100和200 mM甘露醇）和盐度（0、150和300 mM NaCl）以及除草剂胁迫（敌草快）下进行了测试。我们的结果表明，与野生型植物相比，转质体品系对除草剂诱导的氧化和盐胁迫具有耐受性，并且对甘露醇诱导的渗透胁迫表现出增强的响应耐受性。叶绿体中GSTT的过表达导致在胁迫下光耐受性增强和膨压维持。全基因组转录组分析表明，在对照和高甘露醇胁迫条件下，与胁迫耐受性相关的基因在转质体2a品系中上调。在叶绿体中过表达pt 2a的转质体植物表现出对胁迫的适应状态，因为与野生型相比，在胁迫条件下转质体2a转质体系中只有有限数量的基因上调，而与此同时，与胁迫耐受性相关的基因在无胁迫条件下的转质体2a植物中比野生型上调。同时，代谢谱表明转质体系中代谢稳态的扰动有限，并且在高甘露醇胁迫下甘露醇和可溶性糖的积累更多。因此，转质体系在无胁迫条件下似乎处于对胁迫的适应状态，即使在高甘露醇胁迫下也能维持。这些结果有助于阐明GSTs在植物非生物胁迫耐受性中的作用以及叶绿体中表达的GSTs对栽培作物环境适应性的潜在机制。
