Spatial scaling of soil microbial co-occurrence networks in a fragmented landscape

Impact statement Habitat loss has been a primary threat to biodiversity.However,species do not function in isolation but often associate with each other and form complex networks.Thus,revealing how the network complexity and stability scale with habitat area will give us more insights into the effects of habitat loss on ecosystems.In this study,we explored the relationships between the island area and the network complexity and stability of soil microbes.We found that the complexity and stability of soil microbial co‐occurrence networks scale positively with island area,indicating that habitat loss will potentially simplify and destabilize soil microbial networks.

Disruption of the Arabidopsis Defense Regulator Genes SAG101, EDS1, and PAD4 Confers Enhanced Freezing Tolerance

In Arabidopsis, three lipase-like regulators, SAG101, EDS1, and PAD4, act downstream of resistance protein-associated defense signaling. Although the roles of SAG101, EDS1, and PAD4 in biotic stress have been extensively studied, little is known about their functions in plant responses to abiotic stresses. Here, we show that SAG101, EDS1, and PAD4 are involved in the regulation of freezing tolerance in Arabidopsis. With or without cold acclimation, the sag101, edsl, and pad4 single mutants, as well as their double mutants, exhibited similarly enhanced tolerance to freezing temperatures. Upon cold exposure, the sag101, edsl, and pad4 mutants showed increased transcript levels of C-REPEAT/DRE BINDING FACTORs and their regulons compared with the wild type. Moreover, freezing-induced cell death and accumulation of hydrogen peroxide were ameliorated in sag101, edsl, and pad4 mutants. The sag101, edsl, and pad4 mutants had much lower salicylic acid （SA） and diacylglycerol （DAG） contents than the wild type, and exogenous application of SA and DAG compromised the freezing tolerance of the mutants. Furthermore, SA suppressed the cold-induced expression of DGATs and DGKs in the wild-type leaves. These findings indicate that SAG101, EDS1, and PAD4 are involved in the freezing response in Arabidopsis, at least in part, by modulating the homeostasis of SA and DAG.

丛枝菌根真菌数个种的基因组和转录组研究概况

丛枝菌根真菌(AMF)在自然界分布广泛,能与大部分维管植物的根系形成菌根共生体。它们在调节植物群落结构和全球的碳、氮、磷循环等方面发挥着重要的生态功能,也是农林、环境领域最具应用前景的微生物类群。受限于培养方法、研究手段等,长期以来对AMF基因组、转录组特征的认识非常有限。最近10年,AMF基因组和转录组的相关研究在高通量测序技术的推动下取得了较快发展;研究结果也显著提高了对AMF遗传发育、代谢生理、共生机制等的认识。本文综述了目前已完成测序的AMF种类的基因组、转录组信息。结果发现,已测序的AMF种类普遍具有基因组大、转座子丰富、AT碱基含量高、含大量未知功能基因与特异性基因、缺少部分共生相关基因等特点。在转录层面,总结了不同AMF种类、AMF不同共生结构、共生阶段以及与不同寄主植物共生时的转录本特征。结果发现,不同种类AMF的转录本大小差异明显。不同共生阶段或不同共生结构中的AMF转录本也具有较大的差异,且差异表达的基因大部分与养分交易、信号转导等密切相关。相比之下,同种AMF与不同寄主植物共生时的转录本表现出较高的保守性。最后,本文提出了本领域需要重点关注的研究方向,包括AMF纯培养技术的革新、AMF基因功能的解析、非模式AMF类群的研究以及对AMF蛋白组的研究。

Resistance potential of soil bacterial communities along a biodiversity gradient in forest ecosystems

Higher biodiversity is often assumed to be a more desirable scenario for maintaining the functioning of ecosystems,but whether species-richer communities are also more disturbance-tolerant remains controversial.In this study,we investigated the bacterial communities based on 472 soil samples from 28 forests across China with associated edaphic and climatic properties.We developed two indexes(i.e.,community mean tolerance breadth[CMTB]and community mean response asynchrony[CMRA])to explore the relationship between diversity and community resistance potential.Moreover,we examined this resistance potential along the climatic and latitudinal gradients.We revealed that CMTB was significantly and negatively related to species richness,resulting from the changes in balance between relative abundances of putative specialists and generalists.In comparison,we found a unimodal relationship between CMRA and richness,suggesting that higher biodiversity might not always lead to higher community resistance.Moreover,our results showed differential local patterns along latitude.In particular,local patterns in the northern region mainly followed general relationships rather than those for the southern forests,which may be attributed to the differences in annual means and annual variations of climate conditions.Our findings highlight that the community resistance potential depends on the composition of diverse species with differential environmental tolerance and responses.This study provides a new,testable evaluation by considering tolerance breadth and response asynchrony at the community level,which will be helpful in assessing the influence of disturbance under rapid shifts in biodiversity and species composition as a result of global environmental change.

Comparative genomic analysis of Thermus provides insights into the evolutionary history of an incomplete denitrification pathway

Biological denitrification is a crucial process in the nitrogen biogeochemical cycle,and Thermus has been reported to be a significant heterotrophic denitrifier in terrestrial geothermal environments.However,neither the denitrification potential nor the evolutionary history of denitrification genes in the genus Thermus or phylum Deinococcota is well understood.Here,we performed a comparative analysis of 23 Thermus genomes and identified denitrification genes in 15 Thermus strains.We confirmed that Thermus harbors an incomplete denitrification pathway as none of the strains contain the nosZ gene.Ancestral character state reconstructions and phylogenetic analyses showed that narG,nirS,and norB genes were acquired by the last common ancestor of Thermales and were inherited vertically.In contrast,nirK of Thermales was acquired via two distinct horizontal gene transfers from Proteobacteria to the genus Caldithermus and from an unknown donor to the common ancestor of all known Thermus species except Thermus filiformis.This study expands our understanding of the genomic potential for incomplete denitrification in Thermus,revealing a largely vertical evolutionary history of the denitrification pathway in the Thermaceae,and supporting the important role for Thermus as an important heterotrophic denitrifier in geothermal environments.