丛枝菌根真菌通过改变植物基因表达水平和微生物群落结构促进红叶石楠对镉的吸收

Arbuscular mycorrhizal fungi enhanced cadmium uptake in Photinia frase through altering root transcriptomes and root-associated microbial communities

摘要:

作为一种非必需元素，重金属镉(cadmium, Cd) 的污染对植物、环境乃至人类健康具有严重影响。利用绿化苗木移栽修复Cd污染土壤具有广阔的应用前景。为了明确丛枝菌根真菌(arbuscular mycorrhizal fungi, AMF)对红叶石楠(Photinifraseri frase) Cd吸收的促进作用，本研究利用盆栽试验比较了接种扭形伞房球囊霉(Sieverdingia tortuosa) 和摩西斗管囊霉(Funneliformis mosseae) 后红叶石楠的生长和Cd吸收差异，并利用转录组和微生物组测序技术分析了接种对红叶石楠根系基因表达水平和根围微生物群落结构的影响。结果表明，接种摩西斗管囊霉后，红叶石楠根、茎、叶中Cd浓度相比对照分别增加了57.2%、44.1%和71.1%，全株Cd含量达到182 μg/株。东京基因与基金组百科全书(Kyoto encyclopedia of genes and genomes, KEGG) 代谢通路分析结果表明，接种摩西斗管囊霉影响了植物蛋白激酶(mitogen-activated protein kinase, MAPK) 信号通路、植物激素信号转导、糖酵解/糖异生和次生代谢产物的生物合成等相关基因的表达。微生物群落结构分析表明，接种扭形伞房球囊霉增加了酸杆菌门(Acidobacteria) 的相对丰度，而接种摩西斗管囊霉则增加了土壤中绿弯菌门(Chloroflexi) 和髌骨细菌门(Patescibacteria) 的相对丰度。接种AMF后球囊霉目(Glomerales) 丰度显著增加，由对照的23%上升至70%以上。相关性分析结果显示，乙烯反应转录因子、α-氨基己二酸半醛合酶、异淀粉酶和胍丁胺脱氨酶等基因表达与球囊霉目丰度显著负相关，半胱氨酸氧化、热休克蛋白、肉桂酰辅酶A还原酶和脱落酸受体等相关基因表达与髌骨细菌门丰度呈显著正相关。结果表明，摩西斗管囊霉的接种不仅直接影响了红叶石楠的基因表达水平，促进了红叶石楠对Cd的吸收，而且通过改变红叶石楠根围细菌群落结构，进一步提高了红叶石楠在Cd胁迫条件下的适应性。研究结果为进一步认识植物根系转录组和根围微生物组的相互关系提供了理论依据，并为Cd污染土壤修复提供了一种新的策略。

关键词:丛枝菌根真菌;红叶石楠;镉;土壤修复;转录组测序

Abstract:

As a non-essential metal, cadmium (Cd) pollution poses severe threats to plant growth, environment, and human health. Phytoextraction using nursery stocks prior to their transplantation is a potential useful approach for bioremediation of Cd contaminated soil. A greenhouse pot experiment was performed to investigate the growth, Cd accumulation, profiles of transcriptome as well as root-associated microbiomes of Photinia frase in Cd-added soil, upon inoculation of two types of arbuscular mycorrhizal fungi (AMF) Sieverdingia tortuosa and Funneliformis mosseae. Compared with the control, inoculation of F. mosseae increased Cd concentrations in root, stem and leaf by 57.2%, 44.1% and 71.1%, respectively, contributing to a total Cd content of 182 μg/plant. KEGG pathway analysis revealed that hundreds of genes involved in 'Mitogen-activated protein kinase (MAPK) signaling pathway', 'plant hormone signal transduction', 'biosynthesis of secondary metabolites' and 'glycolysis/gluconeogenesis' were enriched upon inoculation of F. mosseae. The relative abundance of Acidobacteria was increased upon inoculation of S. tortuosa, while Chloroflexi and Patescibacteria were increased upon inoculation of F. mosseae, and the abundance of Glomerales increased from 23.0% to above 70%. Correlation analysis indicated that ethylene-responsive transcription factor, alpha-aminoadipic semialdehyde synthase, isoamylase and agmatine deiminase related genes were negatively associated with the relative abundance of Glomerales operational taxonomic units (OTUs) upon inoculation of F. mosseae. In addition, plant cysteine oxidase, heat shock protein, cinnamoyl-CoA reductase and abscisic acid receptor related genes were positively associated with the relative abundance of Patescibacteria OTUs upon inoculation of F. mosseae. These finding suggested that AMF can enhance P. frase Cd uptake by modulating plant gene expression and altering the structure of the soil microbial community. This study provides a theoretical basis for better understanding the relationship between root-associated microbiomes and root transcriptomes of P. frase, from which a cost-effective and environment-friendly strategy for phytoextraction of Cd in Cd-polluted soil might be developed.

Key words:arbuscular mycorrhizal fungus (AMF);Photinia frase;Cd;soil remediation;RNA-Seq