Selim Samy, Akhtar Nosheen, Hagagy Nashwa, Alanazi Awadh, Warrad Mona, El Azab Eman, Elamir Mohammed Yagoub Mohammed, Al-Sanea Mohammad M, Jaouni Soad K Al, Abdel-Mawgoud Mohamed, Shah Anis Ali, Abdelgawad Hamada
Department of Clinical Laboratory Sciences, College of Applied Medical Sciences, Jouf University, Sakaka, Saudi Arabia.
Department of Biological Sciences, National University of Medical Sciences, Rawalpindi, Pakistan.
Front Plant Sci. 2022 May 19;13:872654. doi: 10.3389/fpls.2022.872654. eCollection 2022.
Soil contamination with cobalt (Co) negatively impacts plant growth and production. To combat Co toxicity, plant growth-promoting microorganisms for improving plant growth are effectively applied. To this end, unclassified haloarchaeal species strain NRS_31 (OL912833), belonging to , was isolated, identified for the first time, and applied to mitigate the Co phytotoxic effects on maize plants. This study found that high Co levels in soil lead to Co accumulation in maize leaves. Co accumulation in the leaves inhibited maize growth and photosynthetic efficiency, inducing oxidative damage in the tissue. Interestingly, pre-inoculation with haloarchaeal species significantly reduced Co uptake and mitigated the Co toxicity. Induced photosynthesis improved sugar metabolism, allocating more carbon to defend against Co stress. Concomitantly, the biosynthetic key enzymes involved in sucrose (sucrose-P-synthase and invertases) and proline (pyrroline-5- carboxylate synthetase (P5CS), pyrroline-5-carboxylate reductase (P5CR)) biosynthesis significantly increased to maintain plant osmotic potential. In addition to their osmoregulation potential, soluble sugars and proline can contribute to maintaining ROS hemostasis. Maize leaves managed their oxidative homeostasis by increasing the production of antioxidant metabolites (such as phenolics and tocopherols) and increasing the activity of ROS-scavenging enzymes (such as POX, CAT, SOD, and enzymes involved in the AsA/GSH cycle). Inside the plant tissue, to overcome heavy Co toxicity, maize plants increased the synthesis of heavy metal-binding ligands (metallothionein, phytochelatins) and the metal detoxifying enzymes (glutathione S transferase). Overall, the improved ROS homeostasis, osmoregulation, and Co detoxification systems were the basis underlying Co oxidative stress, mitigating haloarchaeal treatment's impact.
土壤中的钴（Co）污染会对植物生长和产量产生负面影响。为了对抗钴毒性，有效应用促进植物生长的微生物来改善植物生长。为此，首次分离、鉴定了属于未分类盐古菌物种的菌株NRS_31（OL912833），并将其用于减轻钴对玉米植株的植物毒性作用。本研究发现，土壤中高含量的钴会导致钴在玉米叶片中积累。叶片中的钴积累抑制了玉米生长和光合效率，在组织中引发氧化损伤。有趣的是，用盐古菌物种进行预接种显著减少了钴的吸收并减轻了钴毒性。诱导的光合作用改善了糖代谢，分配更多碳以抵御钴胁迫。与此同时，参与蔗糖（蔗糖磷酸合成酶和转化酶）和脯氨酸（吡咯啉-5-羧酸合成酶（P5CS）、吡咯啉-5-羧酸还原酶（P5CR））生物合成的关键酶显著增加，以维持植物的渗透势。除了其渗透调节潜力外，可溶性糖和脯氨酸有助于维持活性氧稳态。玉米叶片通过增加抗氧化代谢物（如酚类和生育酚）的产生以及增加活性氧清除酶（如POX、CAT、SOD和参与AsA/GSH循环的酶）的活性来维持其氧化稳态。在植物组织内部，为了克服高钴毒性，玉米植株增加了重金属结合配体（金属硫蛋白、植物螯合肽）和金属解毒酶（谷胱甘肽S-转移酶）的合成。总体而言，改善的活性氧稳态、渗透调节和钴解毒系统是减轻钴氧化应激、缓解盐古菌处理影响的基础。
