Entomopathogenic Fungi-Mediated Solubilization and Induction of Fe Related Genes in Melon and Cucumber Plants

Abstract

Endophytic insect pathogenic fungi have a multifunctional lifestyle; in addition to its well-known function as biocontrol agents, it may also help plants respond to other biotic and abiotic stresses, such as iron (Fe) deficiency. This study explores M. brunneum EAMa 01/58-Su strain attributes for Fe acquisition. Firstly, direct attributes include siderophore exudation (in vitro assay) and Fe content in shoots and in the substrate (in vivo assay) were evaluated for three strains of Beauveria bassiana and Metarhizium bruneum. The M. brunneum EAMa 01/58-Su strain showed a great ability to exudate iron siderophores (58.4% surface siderophores exudation) and provided higher Fe content in both dry matter and substrate compared to the control and was therefore selected for further research to unravel the possible induction of Fe deficiency responses, Ferric Reductase Activity (FRA), and relative expression of Fe acquisition genes by qRT-PCR in melon and cucumber plants.. In addition, root priming by M. brunneum EAMa 01/58-Su strain elicited Fe deficiency responses at transcriptional level. Our results show an early up-regulation (24, 48 or 72 h post inoculation) of the Fe acquisition genes FRO1, FRO2, IRT1, HA1, and FIT as well as the FRA. These results highlight the mechanisms involved in the Fe acquisition as mediated by IPF M. brunneum EAMa 01/58-Su strain.

Entomopathogenic Fungus-Related Priming Defense Mechanisms in Cucurbits Impact Spodoptera littoralis (Boisduval) Fitness

“…In the case of EPF, priming could be a very interesting strategy as it is an added value for the fungal efficacy when used for pest control. Usually, microorganism inducers of ISR also promote plant growth and development ( 77 ) and favor Fe acquisition ( 18 , 78 – 83 ). In the present work, we show the ability of the EPF M. brunneum to trigger both SA- and JA/ET-dependent priming in cucumber and melon seedlings with lethal and sublethal effects on S. littoralis fed on primed plants.…”

“…A Metarhizium brunneum (EAMa 01/58-Su) strain from the culture collection of the Agronomy Department, University of Córdoba (Spain), was used in all experiments (Spanish Type Culture Collection accession number 20764 ). Detailed information about the fungal strain can be found in the work of García-Espinoza et al ( 18 ). Transient and temporary endophytic colonization of melon plants by this strain has been previously demonstrated in foliar application ( 5 , 6 ), and the positive effects on growth promotion and response to Fe deficiency of M. brunneum have been described previously ( 107 – 109 ) in several cultivated species.…”

“…Some of these ISR inducer microorganisms also promote plant growth and development ( 77 ) and favor Fe acquisition in plants ( 18 , 78 – 83 ). This is in part due to the common involvement of ET and nitric oxide (NO) in the regulation of both processes and because of the cross talk among ET and JA signaling pathways ( 52 ).…”

“…This is in part due to the common involvement of ET and nitric oxide (NO) in the regulation of both processes and because of the cross talk among ET and JA signaling pathways ( 52 ). The effect of these microorganisms on the improvement of Fe nutrition is related to their ability to upregulate key genes related to Fe acquisition, such as FIT , MYB72 , IRT1 , and FRO2 ( 18 , 52 , 77 , 78 ). On the other hand, MYB72, a key transcription factor (TF) in ISR activation, also participates in the regulation of the Fe deficiency responses through its interaction with FIT TF, a key regulator of Fe deficiency responses.…”

Entomopathogenic fungus Beauveria bassiana–based bioinsecticide suppresses severity of powdery mildews of vegetables by inducing the plant defense responses

“…Iron catalyzes hydrogen peroxide to generate more damaging reactive oxygen species, causing intracellular damage and, ultimately, programmed cell death ( Herlihy et al., 2020 ). On the other hand, iron deficiency activates phytohormones that are used for plant immune signaling, suggesting cross-talk between iron and plant immunity ( Herlihy et al., 2020 ; García-Espinoza et al., 2023 ). A GO term associated with SA, which activates plant immunity to biotrophic and hemibiotrophic pathogens such as powdery mildews ( Zhang and Li, 2019 ), was also detected, including genes encoding a WRKY transcription factor ( CsWRKY59 ) and three BTB/POZ and TAZ proteins.…”