Stress specific signalling between microbes and plants

我研究项目的长期目标是了解植物与微生物相互作用的基本原理，并最终将这些理解应用于农作物。过去的发现基金已经允许我的小组证明微生物对植物的信号可以增强结瘤和固氮，以及植物在逆境条件下的生长。在此，我提出验证一个假设，即受胁迫的日本慢生根瘤菌产生一套改变的化合物，促进固氮共生和植物生长，并且它们对固氮和植物生长的影响大于没有胁迫时产生的微生物信号化合物的影响。豆科植物固氮共生始于豆科植物与根瘤菌伙伴间信号化合物的交换。我们已经证明根瘤菌-豆科植物信号（脂质-壳寡糖，LCOs）也能够直接刺激植物生长，并且当植物受到胁迫时，这种影响要大得多。最近的报道表明，当热带根瘤菌受到胁迫时，它产生的lco与在最佳条件下产生的lco不同，这表明产生了胁迫特异性lco。我们最近对经LCO处理的发芽种子（拟南芥和大豆）进行了蛋白质组学分析，发现与能量代谢和胁迫反应相关的途径中的酶增加，证实了LCO在提高植物抗逆性中的作用。我们将在压力和非压力条件下培养一组具有特征的根瘤菌，并检查培养菌株的肉汁促进植物生长的能力，然后分离和表征在压力条件下产生的新化合物。将比较这些化合物在最佳和逆境条件下对大豆和玉米的影响。我们将使用盐压力，因为它很容易应用。我们将研究这些化合物对发芽、早期生长、光合速率、个体发育（叶片外观、开花、成熟）和总生物量积累的影响。我们将对这些化合物中最有效的进行后续工作。我们还将研究这些信号化合物处理过的胁迫和非胁迫植物的激素谱、基因表达、蛋白质组和代谢组。在需要提高植物生产力来养活不断增长的人口和提供生物燃料，而作物受到日益增加的气候变化的挑战的时候，了解允许开发低投入技术以提高作物耐受性和生产力的现象是非常重要的。我过去的发现资助也集中在微生物到植物的信号上，这导致了基本的理解，使得技术的发展现在每年被应用到几千万公顷的农业用地上。

The long-term objective of my research program has been to understand the basics of plant-microbe interactions, and eventually apply these understandings to crop plants. Past Discovery grant funds have allowed my group to demonstrate that microbe to plant signals can enhance nodulation and N2 fixation, and plant growth under conditions stressful to plant growth. Herein I propose to test the hypothesis that stressed Bradyrhizobium japonicum produces an altered suite of compounds that promote the N2-fixing sysmbiosis and plant growth, and that their effects on N2-fixation and plant growth are greater than the effects of the microbial signal compounds produced in the absence of stress. The legume N2-fixation symbiosis begins with exchange of signal compounds between legume and rhizobial partners. We have shown that the rhizobia-to-legume signals (lipo-chitooligosaccharies, LCOs) are also able to directly stimulate plant growth, and that this effect is much larger when plants are stressed. Recent reports have indicated that when Rhizobium tropici is stressed it produces LCOs different from those produced under optimal conditions, suggesting the production of stress-specific LCOs. We have recently conducted proteomic analyses on germinating seeds (Arabidopsis and soybean) treated with LCO and have found that enzymes in pathways related to energy metabolism and stress response are increased, confirming the role of LCOs in improving plant stress tolerance. We will culture a set of characterized rhizobia under stressful and non-stressful conditions and examine the broths in which the strains were grown for ability to enhance plant growth, then isolate and characterize new compounds produced under stressful conditions. These compounds will be compared for effects on soybean and corn under optimal and stressful conditions. We will work with salt stress as it is easy to apply. We will examine the effects of these compounds on: germination, early growth, photosynthetic rates, ontogeny (appearance of leaves, flowering, maturity) and total biomass accumulation. We will conduct subsequent work with the most effective of these compounds. We will also examine the hormone profile, gene expression, proteome and metabolome of stressed and unstressed plants treated with these signal compounds. At a time when increased plant productivity is needed to feed an expanding population and supply biofuels, while crops are challenged by increasing climate variability, understanding phenomena that allow development of low-input technologies that improve crop stress tolerance and productivity is very important. My past discovery grants have also focused on microbe-to-plant signals and this has resulted in basic understandings that allowed the development of technologies now being applied to several 10s of millions ha of agricultural land each year.