Metabonomics Study Of The Response Of Rice To Brown Planthopper

The brown planthopper (Nilaparvata lugens Stal, BPH) is a notorious pest of rice (Oryza sativa L.) regularly occurring throughout the important rice production regions and seriously affecting the global rice production. In 1991, for instance, the affected rice field in China alone accounted for about two million hm2. Prolonged BPH infestation often reduces photosynthetic rates, and subsequently causes reductions in protein, sugars and dry weight of susceptible rice plants,In contrast, resistant rice plants carrying BPH-resistance genes incur little damage and grow normally under BPH attack. Therefore, breeding and growing resistant rice plants is widely accepted to be the most effective and environmentally friendly way to avoid BPH-caused production losses. Understanding the systematic responses to BPH stress in the susceptible and resistant rice plants is the essential part for comprehension of the defensive mechanism of rice plants against BPH, which ought to be helpful for effective development of BPH-resistance rice plants.For the time being, systems metabolic responses of rice plants to BPH attack remain to be thoroughly investigated to ascertain whether other metabolic processes are involved or not and which ones are important to plant resistance to BPH infestation. Information on such responses ought to be obtainable with metabonomics approach since metabonomics is the branch of science concerned with effects of both endogenous and exogenous factors on the holistic metabolic networks of biological systems. To understand systems metabolic responses of rice plants to BPH infestation, we analyzed BPH-induced metabolic changes in leaf sheaths of both BPH-susceptible and resistant rice varieties using NMR-based metabonomics and measured expressions of ten relevant genes using quantitative real-time PCR. Our results showed that rice metabonome was dominated by more than 30 metabolites including sugars, organic acids, amino acids and choline metabolites. BPH infestation caused profound metabolic changes for both BPH-susceptible and resistant rice plants involving transamination, GABA shunt, TCA cycle, gluconeogenesis/glycolysis, pentose phosphate pathway and secondary metabolisms. BPH infestation caused more drastic overall metabolic changes for BPH-susceptible rice and more marked up-regulations for key genes regulating GABA shunt and biosynthesis of secondary metabolites for BPH-resistant variety. Such observations indicated that activation of GABA shunt and shikimate-mediated secondary metabolisms was vital for rice plants to resist BPH infestation. These findings filled the gap of our understandings in the mechanistic aspects of BPH resistance for rice plants and demonstrated the combined metabonomic and qRT-PCR analysis as an effective approach for understanding plant-herbivore interactions.We detected the changes in transcriptome of leaf sheathes of susceptible rice plants TNI and resistant rice plants B5 in response to BPH attack for 6 hour by gene microarray. The results showed that in contrast to the susceptible rice plants, the expressional levels of many genes were up-regulated particularly in the resistant rice plants, including 7 WRKY transcription factors,5 lipoxygenases involved in jasmonic acid pathway, and 1 ACC synthases involved in ethane pathway. In addition, BPH feeding also induced elevated expressional levels of 5 serine/threonine-protein kinases and 2 MAPKs in the resistant rice plants. Furthermore,8 peroxidase,16 cytochrome P450 and 6 phenylalanine ammonia-lyases were activated in the resistant rice plants. Firstly, the results indicate that the resistance of rice plants B5 is dependent on the cross talk of salicylic acid, jasmonic acid and ethane. Secondly, the results also demonstrate that rice plants B5 responded to BPH attack more quickly and timely, and activated an early signal transduction during defense response. Thirdly, antioxidation of peroxidase and detoxication of cytochrome P450, and shikimate-mediated secondary metabolism are closely linked with the resistance of rice plants B5 to BPH attack.Many plants release elevated levels of volatile organic compounds (VOCs) upon insect herbivory. Some herbivore-induced plant volatiles function in indirect plant defense by attracting predators and/or parasitoids that are natural enemies of the feeding herbivores. In our experiments, first, we observe whether the enemy of BPH choose susceptible rice plants TNI or resistant rice plants B5 by Y-tube olfactometer. Then, we collected VOCs by solid-phase microextraction (SPME) and detected the difference between susceptible and resistant rice plants by GC-MS. When we find the different compound, we can spray plants with this compound to observe whether choice disappears. If the choice disappears, we can measure the levels of upstream or downstream compounds, and measure the expressional levels of several important genes involved in this pathway.