Bibi Noreen, Ahmed Imrul Mosaddek, Fan Kai, Dawood Muhammad, Li Feng, Yuan Shuna, Wang Xuede
Institute of Crop Science, College of Agriculture and Biotechnology, Zijingang Campus, Zhejiang University, Hangzhou, 310058, China.
Plant Breeding and Genetics Division, Nuclear Institute for Agriculture and Biology, Faisalabad, Pakistan.
Environ Sci Pollut Res Int. 2017 May;24(13):12281-12292. doi: 10.1007/s11356-017-8738-6. Epub 2017 Mar 29.
Brassinosteroids are well known to mitigate biotic stresses; however, their role to induce tolerance against Verticillium dahliae is unknown. The current study employed V. dahliae (Vd) toxin as pathogen-free model system to induce stress on cotton callus growth, and its amelioration was investigated using 24-epibrassinolide (EBR). Results revealed that EBR has ameliorative effects against Vd toxin with greater seen effect when callus was treated with EBR prior to its exposure to Vd toxin (pre-EBR treatment) than EBR applied along with Vd toxin simultaneously (co-EBR treatment). Pre-EBR-treated calli remained green, while 65 and 90% callus browning was observed in co-EBR- and Vd toxin-alone-treated callus, respectively. Likewise, the fresh weight of the pre-EBR-treated callus was 52% higher than Vd toxin-alone treatment, whereas this increase was only 23% in co-EBR-treated callus. Meanwhile, EBR treatment of the cotton callus has also increased the contents of chlorophylls a and b, carotenoids, total phenols, flavonoids, soluble sugars, and proteins and increased the activity of enzymes involved in secondary metabolism like polyphenol oxidase (PPO), phenylalanine ammonialyase (PAL), cinnamyl alchol dehydrogenase (CAD), and shikimate dehydrogenase (SKDH) over Vd toxin-alone treatment with higher increments being observed in pre-EBR-treated callus. Furthermore, EBR treatment mimicked the DNA damage and improved the structure of mitochondria, granum, stroma thylakoids, and the attachment of ribosomes with the endoplasmic reticulum. This EBR-mediated mitigation was primarily associated with substantially increased contents of photosynthetic pigments and regulation of secondary metabolism.
油菜素甾醇类物质在减轻生物胁迫方面广为人知；然而，它们在诱导棉花对大丽轮枝菌产生耐受性方面的作用尚不清楚。本研究采用大丽轮枝菌（Vd）毒素作为无病原体模型系统，对棉花愈伤组织生长施加胁迫，并使用24-表油菜素内酯（EBR）研究其缓解作用。结果表明，EBR对Vd毒素具有缓解作用，在愈伤组织暴露于Vd毒素之前先用EBR处理（EBR预处理），其效果比与Vd毒素同时施用EBR（EBR共处理）更显著。EBR预处理的愈伤组织保持绿色，而在EBR共处理和单独用Vd毒素处理的愈伤组织中，分别观察到65%和90%的愈伤组织褐变。同样，EBR预处理的愈伤组织鲜重比单独用Vd毒素处理高52%，而在EBR共处理的愈伤组织中，这一增幅仅为23%。同时，对棉花愈伤组织进行EBR处理还增加了叶绿素a和b、类胡萝卜素、总酚、类黄酮、可溶性糖和蛋白质的含量，并提高了参与次生代谢的酶的活性，如多酚氧化酶（PPO）、苯丙氨酸解氨酶（PAL）、肉桂醇脱氢酶（CAD）和莽草酸脱氢酶（SKDH），与单独用Vd毒素处理相比，EBR预处理的愈伤组织中这些酶的活性增加幅度更大。此外，EBR处理模拟了DNA损伤并改善了线粒体、叶绿体基粒、基质类囊体的结构以及核糖体与内质网的附着。这种EBR介导的缓解作用主要与光合色素含量的大幅增加和次生代谢的调节有关。
