Promotion of Arabidopsis immune responses by a rhizosphere fungus via supply of pipecolic acid to plants and selective augment of phytoalexins

The ascomycete insect pathogenic fungi such as Metarhizium species have been demonstrated with the abilities to form the rhizosphere or endophytic relationships with different plants for nutrient exchanges.In this study,after the evident infeasibility of bacterial disease development in the boxed sterile soils,we established a hydroponic system for the gnotobiotic growth of Arabidopsis thaliana with the wild-type and transgenic strain of Metarhizium robertsii.The transgenic fungus could produce a high amount of pipecolic acid(PIP),a pivotal plant-immune-stimulating metabolite.Fungal inoculation experiments showed that M.robertsii could form a non-selective rhizosphere relationship with Arabidopsis.Similar to the PIP uptake by plants after exogenous application,PIP level increased in Col-0 and could be detected in the PIP-non-producing Arabidopsis mutant(ald1)after fungal inoculations,indicating that plants can absorb the PIP produced by fungi.The transgenic fungal strain had a better efficacy than the wild type to defend plants against the bacterial pathogen and aphid attacks.Contrary to ald1,fmo1 plants could not be boosted to resist bacterial infection after treatments.After fungal inoculations,the phytoalexins camalexin and aliphatic glucosinolate were selectively increased in Arabidopsis via both PIP-dependent and-independent ways.This study unveils the potential mechanism of the fungus-mediated beneficial promotion of plant immunity against biological stresses.The data also highlight the added values of M.robertsii to plants beyond the direct suppression of insect pest populations.

New Metabolic Alterations and A Predictive Marker Pipecolic Acid in Sera for Esophageal Squamous Cell Carcinoma

Esophageal squamous cell carcinoma(ESCC)is a major histological subtype of esophageal cancer with a poor prognosis.Although several serum metabolomic investigations have been reported,ESCC tumor-associated metabolic alterations and predictive biomarkers in sera have not been defined.Here,we enrolled 34 treatment-naive patients with ESCC and collected their pre-and post-esophagectomy sera together with the sera from 34 healthy volunteers for a metabolomic survey.Our comprehensive analysis identified ESCC tumor-associated metabolic alterations as represented by a panel of 12 serum metabolites.Notably,postoperative abrosia and parenteral nutrition substantially perturbed the serum metabolome.Furthermore,we performed an examination using sera from carcinogen-induced mice at the dysplasia and ESCC stages and identified three ESCC tumor-associated metabolites conserved between mice and humans.Notably,among these metabolites,the level of pipecolic acid was observed to be progressively increased in mouse sera from dysplasia to cancerization,and it could be used to accurately discriminate between mice at the dysplasia stage and healthy control mice.Furthermore,this metabolite is essential for ESCC cells to restrain oxidative stress-induced DNA damage and cell proliferation arrest.Together,this study revealed a panel of 12 ESCC tumor-associated serum metabolites with potential for monitoring therapeutic efficacy and disease relapse,presented evidence for refining parenteral nutrition composition,and highlighted serum pipecolic acid as an attractive biomarker for predicting ESCC tumorigenesis.