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【PNAS 等】缺磷下根瘤菌--鹰嘴豆共生适应性依赖于植物代谢重组
发布时间:2016-07-25  来源:土壤与农业可持续发展国家重点实验室  浏览:485

【苔藓秘密的三物种共生】Toby Spribille1,2,*, Veera Tuovinen3,4, Philipp Resl1, Dan Vanderpool2, Heimo Wolinski5, M. Catherine Aime6, Kevin Schneider1,, Edith Stabentheiner1, Merje Toome-Heller6,, Göran Thor4, Helmut Mayrhofer1, Hanna Johannesson3, John P. McCutcheon2,7. Basidiomycete yeasts in the cortex of ascomycete macrolichens. Science, 2016, DOI: 10.1126/science.aaf8287

Abstract

For over 140 years, lichens have been regarded as a symbiosis between a single fungus, usually an ascomycete, and a photosynthesizing partner. Other fungi have long been known to occur as occasional parasites or endophytes, but the one lichen–one fungus paradigm has seldom been questioned. Here we show that many common lichens are composed of the known ascomycete, the photosynthesizing partner, and, unexpectedly, specific basidiomycete yeasts. These yeasts are embedded in the cortex, and their abundance correlates with previously unexplained variations in phenotype. Basidiomycete lineages maintain close associations with specific lichen species over large geographical distances and have been found on six continents. The structurally important lichen cortex, long treated as a zone of differentiated ascomycete cells, appears to consistently contain two unrelated fungi.

  苔藓已知是由2个不同物种(一种真菌及一种能进行光合作用的共生体)组成的生物体,但现在的新的研究揭示,第三个物种也对这一共生关系有贡献。在140多 年中,科学家们知道,苔藓由真菌和藻类(蓝藻)组成,它们对苔藓本身的存在缺一不可。最近,有人提出另一个物种对形成完整、有功能叶状体可能也扮演着某种 作用;叶状体是苔藓的叶状或丛生状结构。因此,为做进一步调查,Toby Spribille等将目光转向2种苔藓:Bryoria fremontiiB. tortuosa,它们会产生毒性物质狐衣酸。这种酸的产生导致B. tortuosa出现淡黄色,而B. fremontii的 颜色则为棕色;科学家们不理解是什么引起这一差异。奇怪的是,近来的系统发育分析无法发现在这2类苔藓间就其真菌品种或光合作用部分有任何实质性的基因序 列差异。因此,Toby Spribille等从美国蒙大拿州的不同地方采集了15个样本,并对其进行了mRNA测序。他们的数据揭示了反映Cyphobasidium的506个基因特征,Cyphobasidium是一种属于担子菌门的酵母菌,后者会在狐衣酸大量存在时变得更为丰富。在进一步调查后,该团队发现了与来自6个大陆52个苔藓属相关的其它担子菌系。通过将Cyphobasidium与其最接近的亲缘物种进行比较分析表明,Cyphobasidium可能是在许多苔藓演化时一同演化的,暗示存在着一个悠久的与组成苔藓的其它物种一同演化的历史。当研究人员去掉Cyphobasidium时,他们发现在苔藓的皮层内有死细胞,提示Cyphobasidium的存在对苔藓的健康至关重要。(来源:EurekAlert!)


【地下水和蒸腾作用】Reed M. Maxwell, Laura E. Condon. Connections between groundwater flow and transpiration partitioning. Science, 2016, Vol. 353, Issue 6297, pp. 377-380, DOI: 10.1126/science.aaf7891

Abstract

Understanding freshwater fluxes at continental scales will help us better predict hydrologic response and manage our terrestrial water resources. The partitioning of evapotranspiration into bare soil evaporation and plant transpiration remains a key uncertainty in the terrestrial water balance. We used integrated hydrologic simulations that couple vegetation and land-energy processes with surface and subsurface hydrology to study transpiration partitioning at the continental scale. Both latent heat flux and partitioning are connected to water table depth, and including lateral groundwater flow in the model increases transpiration partitioning from 47 ± 13 to 62 ± 12%. This suggests that lateral groundwater flow, which is generally simplified or excluded in Earth system models, may provide a missing link for reconciling observations and global models of terrestrial water fluxes.


【缺磷下根瘤菌--鹰嘴豆共生适应性依赖于植物代谢重组】Maryam Nasr Esfahania, Miyako Kusanob,c, Kien Huu Nguyend,e, Yasuko Watanabee, Chien Van Hae, Kazuki Saitoc,f, Saad Suliemang, Luis Herrera-Estrellah,1, and Lam-Son Phan Trand,e,1. Adaptation of the symbiotic Mesorhizobium–chickpea relationship to phosphate deficiency relies on reprogramming of whole-plant metabolism. PNAS, 2016, doi: 10.1073/pnas.1609440113

Abstract

Low inorganic phosphate (Pi) availability is a major constraint for efficient nitrogen fixation in legumes, including chickpea. To elucidate the mechanisms involved in nodule acclimation to low Pi availability, two Mesorhizobium–chickpea associations exhibiting differential symbiotic performances, Mesorhizobium ciceri CP-31 (McCP-31)–chickpea and Mesorhizobium mediterranum SWRI9 (MmSWRI9)–chickpea, were comprehensively studied under both control and low Pi conditions. MmSWRI9–chickpea showed a lower symbiotic efficiency under low Pi availability than McCP-31–chickpea as evidenced by reduced growth parameters and down-regulation of nifD and nifK. These differences can be attributed to decline in Pi level in MmSWRI9-induced nodules under low Pi stress, which coincided with up-regulation of several key Pi starvation-responsive genes, and accumulation of asparagine in nodules and the levels of identified amino acids in Pi-deficient leaves of MmSWRI9-inoculated plants exceeding the shoot nitrogen requirement during Pi starvation, indicative of nitrogen feedback inhibition. Conversely, Pi levels increased in nodules of Pi-stressed McCP-31–inoculated plants, because these plants evolved various metabolic and biochemical strategies to maintain nodular Pi homeostasis under Pi deficiency. These adaptations involve the activation of alternative pathways of carbon metabolism, enhanced production and exudation of organic acids from roots into the rhizosphere, and the ability to protect nodule metabolism against Pi deficiency-induced oxidative stress. Collectively, the adaptation of symbiotic efficiency under Pi deficiency resulted from highly coordinated processes with an extensive reprogramming of whole-plant metabolism. The findings of this study will enable us to design effective breeding and genetic engineering strategies to enhance symbiotic efficiency in legume crops.

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