Department of Plant Sciences, Quaid-I-Azam University, Islamabad, Pakistan.
Department of Biosciences, University of Wah, Wah Cantt, Pakistan.
Sci Rep. 2019 Feb 14;9(1):2097. doi: 10.1038/s41598-019-38702-8.
The plant growth promoting rhizobacteria (PGPR) and plant growth regulators (PGRs) can be applied to improve the growth and productivity of plants, with potential to be used for genetic improvement of drought tolerance. However, for genetic improvement to be achieved, a solid understanding of the physiological and biochemical changes in plants induced by PGPR and PGR is required. The present study was carried out to investigate the role of PGPR and PGRs on the physiology and biochemical changes in chickpea grown under drought stress conditions and their association with drought tolerance. The PGPR, isolated from the rhizosphere of chickpea, were characterized on the basis of colony morphology and biochemical characters. They were also screened for the production of indole-3-acetic acid (IAA), hydrogen cyanide (HCN), ammonia (NH), and exopolysaccharides (EPS) production. The isolated PGPR strains, named P1, P2, and P3, were identified by 16S-rRNA gene sequencing as Bacillus subtilis, Bacillus thuringiensis, and Bacillus megaterium, respectively. The seeds of two chickpea varieties, Punjab Noor-2009 (drought sensitive) and 93127 (drought tolerant) were soaked for 2-3 h prior to sowing in 24 h old cultures of isolates. The salicylic acid (SA) and putrescine (Put) were sprayed (150 mg/L) on 25 day old chickpea seedlings. The results showed that chickpea plants treated with a consortium of PGPR and PGRs significantly enhanced the chlorophyll, protein, and sugar contents compared to irrigated and drought conditions. Leaf proline content, lipid peroxidation, and activities of antioxidant enzymes (CAT, APOX, POD, and SOD) all increased in response to drought stress but decreased due to the PGPR and PGRs treatment. An ultrahigh performance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS) analysis was carried out for metabolic profiling of chickpea leaves planted under controlled (well-irrigated), drought, and consortium (drought plus PGPR and PGRs) conditions. Proline, L-arginine, L-histidine, L-isoleucine, and tryptophan were accumulated in the leaves of chickpea exposed to drought stress. Consortium of PGPR and PGRs induced significant accumulation of riboflavin, L-asparagine, aspartate, glycerol, nicotinamide, and 3-hydroxy-3-methyglutarate in the leaves of chickpea. The drought sensitive chickpea variety showed significant accumulation of nicotinamide and 4-hydroxy-methylglycine in PGPR and PGR treated plants at both time points (44 and 60 days) as compared to non-inoculated drought plants. Additionally, arginine accumulation was also enhanced in the leaves of the sensitive variety under drought conditions. Metabolic changes as a result of drought and consortium conditions highlighted pools of metabolites that affect the metabolic and physiological adjustments in chickpea that reduce drought impacts.
植物生长促进根际细菌（PGPR）和植物生长调节剂（PGRs）可用于改善植物的生长和生产力，并有可能用于提高耐旱性的遗传改良。然而，要实现遗传改良，就需要对 PGPR 和 PGR 诱导植物的生理生化变化有一个坚实的理解。本研究旨在探讨 PGPR 和 PGR 对干旱胁迫条件下鹰嘴豆生长的生理生化变化的作用及其与耐旱性的关系。从鹰嘴豆根际分离出的 PGPR 是根据菌落形态和生化特性进行表征的。还筛选了它们对吲哚-3-乙酸（IAA）、氢氰酸（HCN）、氨（NH）和胞外多糖（EPS）产生的生产。分离出的 PGPR 菌株，分别命名为 P1、P2 和 P3，通过 16S-rRNA 基因测序鉴定为枯草芽孢杆菌、苏云金芽孢杆菌和巨大芽孢杆菌。在播种前，将两个鹰嘴豆品种 Punjab Noor-2009（耐旱敏感）和 93127（耐旱）的种子在 24 小时龄的分离物中浸泡 2-3 小时。在 25 天大的鹰嘴豆幼苗上喷洒（150mg/L）水杨酸（SA）和腐胺（Put）。结果表明，与灌溉和干旱条件相比，用 PGPR 和 PGR 混合物处理的鹰嘴豆植株显著提高了叶绿素、蛋白质和糖的含量。叶片脯氨酸含量、脂质过氧化和抗氧化酶（CAT、APOX、POD 和 SOD）的活性均随干旱胁迫而增加，但由于 PGPR 和 PGR 处理而降低。对在对照（充分灌溉）、干旱和混合物（干旱加 PGPR 和 PGRs）条件下种植的鹰嘴豆叶片进行了超高效液相色谱-高分辨质谱（UPLC-HRMS）分析，进行了代谢组学分析。脯氨酸、L-精氨酸、L-组氨酸、L-异亮氨酸和色氨酸在暴露于干旱胁迫的鹰嘴豆叶片中积累。PGPR 和 PGR 混合物诱导了在鹰嘴豆叶片中显著积累核黄素、L-天冬酰胺、天冬氨酸、甘油、烟酰胺和 3-羟基-3-甲基戊二酸。与未接种干旱植物相比，在两个时间点（44 和 60 天），PGPR 和 PGR 处理的敏感品种鹰嘴豆植株中，脯氨酸和 4-羟基甲基甘氨酸的积累也显著增加。在干旱条件下，敏感品种的精氨酸积累也增强。干旱和混合物条件下的代谢变化突出了影响鹰嘴豆代谢和生理调节从而减轻干旱影响的代谢物池。
