Department of Plant Sciences, Quaid-i-Azam University, Islamabad, 45320, Pakistan.
Department of Biotechnology, Quaid-i-Azam University, Islamabad, Pakistan.
Plant Physiol Biochem. 2019 Jun;139:569-577. doi: 10.1016/j.plaphy.2019.03.041. Epub 2019 Apr 1.
Plant growth-promoting endophytes (PGPEs) can colonize the internal tissues of plants and are capable of promoting plant growth. These bacteria can improve plant tolerance against various biotic and abiotic stresses via the expression of antioxidant enzymes and the production of 1-aminocyclopropane-1-carboxylate (ACC) deaminase. Two salt-tolerant PGPEs, Kocuria rhizophila: KF875448 (14ASP) and Cronobacter sakazakii: KM042090 (OF115), with ACC deaminase activity were investigated for their potential to ameliorate plant salinity stress. The wheat varieties Pasban 90 and Khirman were subjected to two levels of salt stress (80 and 160 mM NaCl) under greenhouse conditions by using a completely randomized design. Analyses of plant growth parameters, antioxidant enzyme activities, chlorophyll and plant mineral contents were conducted to investigate the stress tolerance induced by the PGPEs. The ACC utilization by the PGPEs directly relates to the promotion of plant growth due to the lowering of excess ethylene production under salt stress. High levels of NaCl exhibited negative effects in both varieties. However, inoculation with PGPEs increased the morphological traits and antioxidant activities of the plants while decreasing the Na contents in all treatments compared to uninoculated treatment. Wheat variety Pasban 90 was more tolerant than Khirman in to salt stress in all the measured morphological and biochemical parameters, while the bacterial strain OF115 performed significantly better in all morphological and biochemical parameters, such as fresh dry weight, root shoot length, proline and chlorophyll contents, compared to strain 14ASP. The K/Na ratio in the tissues of bacterial treated plants was higher than the control, probably in order to maintain the nutrient balance. The results of our study revealed that the inoculation of plants by ACC deaminase-producing PGPEs is a potential tool for the enhancement of plant growth and stress tolerance. Moreover, endophytic bacteria allied with host plants are capable of enduring high saline conditions and can interact with plants in a very efficient way.
植物促生内生菌（PGPEs）能够定殖于植物的内部组织，并促进植物生长。这些细菌可以通过表达抗氧化酶和产生 1-氨基环丙烷-1-羧酸（ACC）脱氨酶来提高植物对各种生物和非生物胁迫的耐受性。本研究选用具有 ACC 脱氨酶活性的两株耐盐 PGPEs，即玫瑰色微球菌：KF875448（14ASP）和阪崎克罗诺杆菌：KM042090（OF115），来研究它们缓解植物盐胁迫的潜力。采用完全随机设计，在温室条件下，用两种盐胁迫水平（80 和 160 mM NaCl）处理 Pasban 90 和 Khirman 两个小麦品种。分析植物生长参数、抗氧化酶活性、叶绿素和植物矿物质含量，以研究 PGPEs 诱导的胁迫耐受性。PGPEs 对 ACC 的利用与促进植物生长直接相关，因为它降低了盐胁迫下过量乙烯的产生。高浓度的 NaCl 对两个品种都有负面影响。然而，与未接种处理相比，接种 PGPEs 增加了植物的形态特征和抗氧化活性，同时降低了所有处理中的 Na 含量。在所有测量的形态和生化参数中，Pasban 90 小麦品种比 Khirman 更耐受盐胁迫，而细菌菌株 OF115 在所有形态和生化参数方面的表现明显优于菌株 14ASP，例如鲜干重、根长、茎长、脯氨酸和叶绿素含量。与对照相比，处理过的植物组织中的 K/Na 比值更高，可能是为了维持养分平衡。我们的研究结果表明，接种 ACC 脱氨酶产生的 PGPEs 是增强植物生长和胁迫耐受性的一种潜在工具。此外，与宿主植物共生的内生细菌能够耐受高盐条件，并以非常有效的方式与植物相互作用。
