微柱体筛选法：一种新型的植物促生根际细菌的筛选方法。
The Microphenotron: a novel method for screening plant growth-promoting rhizobacteria.
机构信息
Institute of Microbiology and Molecular Genetics, University of the Punjab, Lahore, Punjab, Pakistan.
Department of Microbiology, Balochistan University of Information Technology, Engineering and Management Sciences (BUITEMS) Quetta, Quetta, Balochistan, Pakistan.
出版信息
PeerJ. 2022 May 13;10:e13438. doi: 10.7717/peerj.13438. eCollection 2022.
BACKGROUND
The 'Microphenotron' is an automated screening platform that uses 96-well microtiter plates to test the response of seedlings to natural products. This system allows monitoring the phenotypic effect of a large number of small molecules. Here, this model system was used to study the effect of phytohormones produced by plant growth-promoting rhizobacteria (PGPR) on the growth of wild-type and mutant lines of .
METHODS
In the present study, high-throughput screening based on 'Microphenotron' was used to screen PGPRs. Rhizobacteria were isolated from the rhizosphere of , which was growing in saline habitats. The phylogeny of these rhizobacteria was determined by 16S rRNA gene sequencing. Strains were screened for plant growth-promoting traits such as auxin production, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, and phosphate solubilization. Ultra-Performance Liquid Chromatography (UPLC) was used to detect the presence of different indolic compounds. Finally, PGPR were evaluated to enhance the growth of in the 'Microphenotron' system and pot trials.
RESULTS
Selected rhizobacteria strains showed positive results for multiple plant-growth promoting traits. For instance, strain (S-6) of exhibited the highest ACC-deaminase activity. UPLC analysis indicated the presence of different indolic compounds in bacterial extracts that included indole lactic acid (ILA), indole carboxylic acid (ICA), and indole-3-acetic acid (IAA). Two strains (S-7 and S-11) of produced the most IAA, ICA and ILA. A screening bioassay through 96-well microtiter plates with wild-type Col. N6000 showed an increase in root growth and proliferation. The highest twofold increase was recorded in root growth with S-26 and S-50. In pot trials, mutant lines of impaired for auxin signaling showed that S-6, S-11, S-24 and S-26 used auxin signaling for plant growth promotion. Similarly, for ethylene insensitive mutant lines ( and ), S-3, S-6, S-7, S-24, and S-26 showed the involvement of ethylene signaling. However, the growth promotion pattern for most of the strains indicated the involvement of other mechanisms in enhancing plant growth. The result of Microphenotron assays generally agreed with pot trials with mutant and wild type varieties. Bacterial strains that induced the highest growth response by these cultivars in the 'Microphenotron' promoted plant growth in pot trials. This suggests that Microphenotron can accelerate the evaluation of PGPR for agricultural applications.
背景
“Microphenotron”是一种自动化筛选平台，它使用 96 孔微量滴定板来测试幼苗对天然产物的反应。该系统可以监测大量小分子的表型效应。在这里，该模型系统被用于研究植物促生根际细菌（PGPR）产生的植物激素对野生型和突变体的生长的影响。
方法
在本研究中，基于“Microphenotron”的高通量筛选用于筛选 PGPR。从生长在盐生栖息地的根际中分离出根际细菌。通过 16S rRNA 基因测序确定这些根际细菌的系统发育。筛选具有生长素产生、1-氨基环丙烷-1-羧酸（ACC）脱氨酶活性和磷酸盐溶解等植物促生特性的菌株。超高效液相色谱法（UPLC）用于检测不同吲哚化合物的存在。最后，评估 PGPR 以增强“Microphenotron”系统和盆栽试验中 的生长。
结果
所选根际细菌菌株在多种植物生长促进特性方面表现出阳性结果。例如，菌株（S-6）表现出最高的 ACC 脱氨酶活性。UPLC 分析表明，细菌提取物中存在不同的吲哚化合物，包括吲哚乳酸（ILA）、吲哚羧酸（ICA）和吲哚-3-乙酸（IAA）。两种菌株（S-7 和 S-11）产生最多的 IAA、ICA 和 ILA。用野生型 Col. N6000 通过 96 孔微量滴定板进行的筛选生物测定显示根生长和增殖增加。在根生长方面，最高的两倍增加记录在 S-26 和 S-50。在盆栽试验中，生长素信号受损的 突变体显示 S-6、S-11、S-24 和 S-26 利用生长素信号促进植物生长。同样，对于乙烯不敏感突变体（ 和 ），S-3、S-6、S-7、S-24 和 S-26 显示乙烯信号的参与。然而，大多数菌株的生长促进模式表明，在增强植物生长方面涉及其他机制。微量滴定板试验的结果通常与突变体和野生型 的盆栽试验结果一致。在“Microphenotron”中，这些品种诱导的最高生长反应的细菌菌株在盆栽试验中促进了植物的生长。这表明 Microphenotron 可以加速农业应用中 PGPR 的评估。
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