撕裂蜡孔菌HG2011对光叶紫花苕结瘤固氮的影响及其潜在机制

【目的】 在我国南方尤其是西南地区,光叶紫花苕(Vicia villosa Roth.)作为重要的青饲和绿肥两用豆科作物被广泛种植,有助于提高土壤氮素和后茬作物的产量品质。接种有益微生物是促进豆科作物生物固氮和生长的重要措施之一。为此,本文研究了一株自主分离获得的白腐真菌¾¾撕裂蜡孔菌(Careporia lacerata HG2011)对光叶紫花苕结瘤固氮和生长的影响,并揭示其潜在机制。【方法】 采用微生物培养、植物培养和田间试验,研究C. lacerata磷铁活化能力、代谢产物构成、与根瘤菌Rhizobium sophorae S3的相互作用,及其对光叶紫花苕结瘤、生长、产量、品质和土壤有效磷铁的影响。【结果】 C. lacerata和根瘤菌之间无拮抗作用。液相色谱-质谱(liquid chromatography-mass spectrometry, LC-MS)分析发现,C. lacerata发酵液含有氨基酸、有机酸和类黄酮等化感物质,能增强根瘤菌的趋化性并促进生物膜形成。此外,C. lacerata还能释放生长素、赤霉素、水杨酸和铁载体,活化难溶性有机和无机磷。在植物培养试验中,单独接种C. lacerata或根瘤菌均能促进光叶紫花苕生长,但以共接种处理效果最佳。C. lacerata定殖于光叶紫花苕根际,导致根长、根系表面积和结瘤数显著增加。田间试验发现,接种C. lacerata显著提高了光叶紫花苕单株根瘤数、根瘤质量和固氮酶活性,以及土壤有效磷铁含量和磷酸酶活性,产量比常规施肥处理增加12.15%且品质无显著变化。【结论】 C. lacerata能够在光叶紫花苕根际定殖,通过分泌化感物质、生长素和活化土壤磷铁等机制促进结瘤固氮和生长发育。C. lacerata易于培养,菌剂制备成本低廉,施用简便,对提高豆科作物产量品质具有一定应用价值。     

硫酸盐对淡水养殖池塘表层底泥微生物的影响

硫酸盐引起的生态学效应已得到了越来越多的关注,但目前关于硫酸盐对养殖池塘底泥微生物的影响还知之甚少。【目的】探究不同浓度硫酸盐对养殖池塘底泥微生物的影响规律及可能的机制。【方法】本研究利用采集自养殖池塘的底泥和表层水构建了试验系统,研究了加入约0 mg/L （对照组）、30 mg/L （T1处理组）、150 mg/L （T2处理组）、500 mg/L （T3处理组） Na₂SO₄后表层底泥微生物的丰度、多样性、组成和共生网络的变化规律,并分析了环境影响因素。【结果】孵育第30天前,各实验组底泥微生物变化不大;但到第50天时,T2和T3处理组微生物丰度和多样性相比对照组均明显下降。相比其他实验组,T1处理组酸杆菌门（Acidobacteriota）、拟杆菌门（Bacteroidota）相对丰度出现显著升高（P<0.05）,T3处理组变形菌门（Proteobacteria）和放线菌门（Actinobacteriota）相对丰度出现显著升高（P<0.05）。与对照组相比,T1处理组增加了较多差异类群（62种）,而T3处理组差异类群大量减少（45种）。共生网络图分析显示硫酸盐浓度的增加引起了底泥微生物网络复杂性的增加,说明微生物群落可能通过自身的调节来响应硫酸盐引起的环境改变。冗余分析（redundant analysis,RDA）和相关性分析揭示底泥总有机碳、总氮和氧化还原电位是影响底泥微生物的主要环境因素,提示底泥微生物可能受到硫酸盐和有机质作用的影响。【结论】较长时间的高浓度硫酸盐会对池塘底泥微生物群落造成重要影响,微生物群落自身的转变和硫酸盐引起的有机质分解改变可能是造成微生物群落变化的关键因素。     

运用α-吡啶羧酸筛选水稻抗稻瘟病细胞变异体的研究

利用α-吡啶羧酸为胁迫因子,研究了花药培养筛选水稻(Oryza sativa L.)抗稻瘟病(Pyricularia oryzae Cav.)细胞变异体的效果。α-吡啶羧酸可抑制水稻花药(粉)愈伤组织的形成与生长,用40mg-L α-吡啶羧酸进行诱导、继代和分化筛选,可获得抗性愈伤组织并再生绿苗,但仅有一半绿苗自然加倍结实,并具备对稻瘟病孢子悬浮液的抗性。经两代选择与鉴定,获得了抗稻瘟病 ZA_1和 ZB_(11)小种、但感 ZG_1小种的变异体2-07和4-091。     

Distribution,causal agents,and infection dynamic of emerging ink disease of sweet chestnut in Southern Switzerland

Emerging diseases caused by both native and exotic pathogens represent a main threat to forest ecosystems worldwide. The two invasive soilborne pathogens Phytophthora cinnamomi and Phytophthora × cambivora are the causal agents of ink disease, which has been threatening Castanea sativa in Europe for several centuries and seems to be re-emerging in recent years. Here, we investigated the distribution, causal agents, and infection dynamics of ink disease in southern Switzerland. A total of 25 outbreaks were identified, 19 with only P. cinnamomi, 5 with only P. × cambivora, and 1 with both species. Dendrochronological analyses showed that the disease emerged in the last 20–30 years. Infected trees either died rapidly within 5–15 years post-infection or showed a prolonged state of general decline until death. Based on a generalized linear model, the local risk of occurrence of ink disease was increased by an S-SE aspect of the chestnut stand, the presence of a pure chestnut stand, management activities, the proximity of roads and buildings, and increasing annual mean temperature and precipitation. The genetic structure of the local P. cinnamomi population suggests independent introductions and local spread of the pathogen.     

Temporal dynamics of soil bacterial network regulate soil resistomes

Soil bacteria are diverse and form complicated ecological networks through various microbial interactions, which play important roles in soil multi-functionality. However, the seasonal effects on the bacterial network, especially the relationship between bacterial network topological features and soil resistomes remains underexplored, which impedes our ability to unveil the mechanisms of the temporal-dynamics of antibiotic resistance genes (ARGs). Here, a field investigation was conducted across four seasons at the watershed scale. We observed significant seasonal variation in bacterial networks, with lower complexity and stability in autumn, and a wider bacterial community niche in summer. Similar to bacterial communities, the co-occurrence networks among ARGs also shift with seasonal change, particularly with respect to the topological features of the node degree, which on average was higher in summer than in the other seasons. Furthermore, the nodes with higher betweenness, stress, degree, and closeness centrality in the bacterial network showed strong relationships with the 10 major classes of ARGs. These findings highlighted the changes in the topological properties of bacterial networks that could further alter antibiotic resistance in soil. Together, our results reveal the temporal dynamics of bacterial ecological networks at the watershed scale, and provide new insights into antibiotic resistance management under environmental changes.     

The potato StMKK5-StSIPK module enhances resistance to Phytophthora pathogens through activating the salicylic acid and ethylene signalling pathways

Mitogen-activated protein kinase (MAPK) cascades play pivotal roles in plant responses to both biotic and abiotic stress. A screen of a Nicotiana benthamiana cDNA virus-induced gene silencing (VIGS) library for altered plant responses to inoculation with Phytophthora infestans previously identified an NbMKK gene, encoding a clade D MAPKK that we renamed as NbMKK5, which is involved in immunity to P. infestans. To study the role of the potato orthologous gene, referred to as StMKK5, in the response to P. infestans, we transiently overexpressed StMKK5 in N. benthamiana and observed that cell death occurred at 2 days postinfiltration. Silencing of the highly conserved eukaryotic protein SGT1 delayed the StMKK5-induced cell death, whereas silencing of the MAPK-encoding gene NbSIPK completely abolished the cell death response. Further investigations showed that StMKK5 interacts with, and directly phosphorylates, StSIPK. Furthermore, both StMKK5 and StSIPK trigger salicylic acid (SA)- and ethylene (Eth)-related gene expression, and co-expression of the salicylate hydroxylase NahG with the negative regulator of Eth signalling CTR1 hampers StSIPK-triggered cell death. This observation indicates that the cell death triggered by StMKK5-StSIPK is dependent on the combination of SA- and Eth-signalling. By introducing point mutations, we showed that the kinase activity of both StMKK5 and StSIPK is required for triggering cell death. Genetic analysis showed that StMKK5 depends on StSIPK to trigger plant resistance. Thus, our results define a potato StMKK5-SIPK module that positively regulates immunity to P. infestans via activation of both the SA and Eth signalling pathways.     

Calcineurin B-like interacting protein kinase 31 confers resistance to sheath blight via modulation of ROS homeostasis in rice

Sheath blight (ShB) severely threatens rice cultivation and production; however, the molecular mechanism of rice defence against ShB remains unclear. Screening of transposon Ds insertion mutants identified that Calcineurin B-like protein-interacting protein kinase 31 (CIPK31) mutants were more susceptible to ShB, while CIPK31 overexpressors (OX) were less susceptible. Sequence analysis indicated two haplotypes of CIPK31: Hap_1, with significantly higher CIPK31 expression, was less sensitive to ShB than the Hap_2 lines. Further analyses showed that the NAF domain of CIPK31 interacted with the EF-hand motif of respiratory burst oxidase homologue (RBOHA) to inhibit RBOHA-induced H₂O₂ production, and RBOHA RNAi plants were more susceptible to ShB. These data suggested that the CIPK31-mediated increase in resistance is not associated with RBOHA. Interestingly, the study also found that CIPK31 interacted with catalase C (CatC); cipk31 mutants accumulated less H₂O₂ while CIPK31 OX accumulated more H₂O₂ compared to the wild-type control. Further analysis showed the interaction of the catalase domain of CatC with the NAF domain of CIPK31 by which CIPK31 inhibits CatC activity to accumulate more H₂O₂.     

The complex genome and adaptive evolution of polyploid Chinese pepper (Zanthoxylum armatum and Zanthoxylum bungeanum)

Zanthoxylum armatum and Zanthoxylum bungeanum, known as ‘Chinese pepper’, are distinguished by their extraordinary complex genomes, phenotypic innovation of adaptive evolution and species-special metabolites. Here, we report reference-grade genomes of Z. armatum and Z. bungeanum. Using high coverage sequence data and comprehensive assembly strategies, we derived 66 pseudochromosomes comprising 33 homologous phased groups of two subgenomes, including autotetraploid Z. armatum. The genomic rearrangements and two whole-genome duplications created large (~4.5 Gb) complex genomes with a high ratio of repetitive sequences (>82%) and high chromosome number (2n = 4x = 132). Further analysis of the high-quality genomes shed lights on the genomic basis of involutional reproduction, allomones biosynthesis and adaptive evolution in Chinese pepper, revealing a high consistent relationship between genomic evolution, environmental factors and phenotypic innovation. Our study provides genomic resources and new insights for investigating diversification and phenotypic innovation in Chinese pepper, with broader implications for the protection of plants under severe environmental changes.     

Upgrading the genome of an elite japonica rice variety Kongyu 131 for lodging resistance improvement

Developing a new rice variety requires tremendous efforts and years of input. To improve the defect traits of the excellent varieties becomes more cost and time efficient than breeding a completely new variety. Kongyu 131 is a high-performing japonica variety with early maturity, high yield, wide adaptability and cold resistance, but the poor-lodging resistance hinders the industrial production of Kongyu 131 in the Northeastern China. In this study, we attempted to improve the lodging resistance of Kongyu 131 from perspectives of both gene and trait. On the one hand, by QTL analysis and fine mapping we discovered the candidate gene loci. The following CRISPR/Cas9 and transgenic complementation study confirmed that Sd1 dominated the lodging resistance and favourable allele was mined for precise introduction and improvement. On the other hand, the Sd1 allelic variant was identified in Kongyu 131 by sequence alignment, then introduced another excellent allelic variation by backcrossing. Then, the two new resulting Kongyu 131 went through the field evaluation under different environments, planting densities and nitrogen fertilizer conditions. The results showed that the plant height of upgraded Kongyu 131 was 17%–26% lower than Kongyu 131 without penalty in yield. This study demonstrated a precise and targeted way to update the rice genome and upgrade the elite rice varieties by improving only a few gene defects from the perspective of breeding.