Second affiliation: Botany and Microbiology Department, Faculty of Science, Kafrelsheikh University, Kafrelsheikh, 33516, Egypt; Dept of Plant Science, University of Manitoba, Winnipeg, R3T2N2, MB, Canada.
Department of Biological Sciences, University of Manitoba, Winnipeg, R3T5Z9, MB, Canada.
J Plant Physiol. 2021 Dec;267:153538. doi: 10.1016/j.jplph.2021.153538. Epub 2021 Oct 2.
Soybean (Glycine max), a major grain crop worldwide, is susceptible to severe yield loss due to drought. Soybean plants over-expressing and downregulating the soybean Phytoblobin1 (GmPgb1) were evaluated for their ability to cope with polyethylene glycol (PEG)-induced water deficit. Sense transformation of GmPgb1, which was more expressed in shoot tissue relative to roots, increased overall plant performance and tolerance to water stress by attenuating the PEG depression of photosynthetic gas exchange parameters and chlorophyll content, as well as reducing leaf injury and promoting root growth. The higher plant relative water content, as a result of GmPgb1 over-expression, was associated with higher transcript levels of three aquaporins: GmTIP1;5 and GmTIP2;5 GmPIP2;9, known to confer water stress tolerance. Opposite results were observed in plants suppressing GmPgb1, which were highly susceptible to PEG-induced stress. Transcriptional and metabolic analyses revealed higher ABA synthesis in dehydrating leaves of plants over-expressing GmPgb1 relative to those suppressing the same gene. The latter plants exhibited a transcriptional induction of ABA catabolic enzymes and higher accumulation of the ABA catabolite dehydrophaseic acid (DPA). Administration of 8'-acetylene ABA, an ABA agonist resistant to the ABA catabolic activity, was sufficient to restore tolerance in the GmPgb1 down-regulating plants suggesting that regulation of ABA catabolism is as important as ABA synthesis in conferring PEG-induced water stress tolerance. Screening of natural soybean germplasm also revealed a rapid and transient increase in foliar GmPgb1 in tolerant plants relative to their susceptible counterparts, thus confirming the key role exercised by this gene during water stress.
大豆（Glycine max）是世界上主要的粮食作物之一，由于干旱，极易减产。为了评估过表达和下调大豆 Phytoblobin1（GmPgb1）的大豆植株对聚乙二醇（PEG）诱导的水分亏缺的适应能力，对其进行了研究。与根部相比，在茎组织中更多表达的 GmPgb1 的正向转化增加了植物的整体性能和对水分胁迫的耐受性，其方式是减弱 PEG 对光合作用气体交换参数和叶绿素含量的抑制作用，减少叶片损伤，促进根系生长。由于 GmPgb1 的过表达，植物的相对含水量更高，这与三个水通道蛋白的转录水平升高有关：GmTIP1;5 和 GmTIP2;5 GmPIP2;9，已知这些蛋白赋予了对水分胁迫的耐受性。在抑制 GmPgb1 的植物中观察到相反的结果，这些植物对 PEG 诱导的胁迫高度敏感。转录和代谢分析显示，与抑制同一基因的植物相比，过表达 GmPgb1 的脱水叶片中 ABA 的合成更高。后一种植物表现出 ABA 分解代谢酶的转录诱导和 ABA 分解代谢物脱氢相位酸（DPA）的更高积累。施用 8'-乙炔基 ABA，一种对 ABA 分解代谢活性有抗性的 ABA 激动剂，足以恢复 GmPgb1 下调植物的耐受性，这表明 ABA 分解代谢的调节与 ABA 合成一样重要，都可以赋予 PEG 诱导的水分胁迫耐受性。对天然大豆种质资源的筛选也显示，与易感对照相比，耐胁迫植物叶片中的 GmPgb1 迅速且短暂增加，从而证实了该基因在水分胁迫过程中的关键作用。
