scholarly journals Bacterial Endophytes: The Hidden Actor in Plant Immune Responses against Biotic Stress

Plants ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 1012
Author(s):  
Nadira Oukala ◽  
Victoria Pastor ◽  
Kamel Aissat

Bacterial endophytes constitute an essential part of the plant microbiome and are described to promote plant health by different mechanisms. The close interaction with the host leads to important changes in the physiology of the plant. Although beneficial bacteria use the same entrance strategies as bacterial pathogens to colonize and enter the inner plant tissues, the host develops strategies to select and allow the entrance to specific genera of bacteria. In addition, endophytes may modify their own genome to adapt or avoid the defense machinery of the host. The present review gives an overview about bacterial endophytes inhabiting the phytosphere, their diversity, and the interaction with the host. Direct and indirect defenses promoted by the plant–endophyte symbiont exert an important role in controlling plant defenses against different stresses, and here, more specifically, is discussed the role against biotic stress. Defenses that should be considered are the emission of volatiles or antibiotic compounds, but also the induction of basal defenses and boosting plant immunity by priming defenses. The primed defenses may encompass pathogenesis-related protein genes (PR family), antioxidant enzymes, or changes in the secondary metabolism.

Author(s):  
Nadira Oukala ◽  
Kamel Aissat ◽  
Victoria Pastor

Bacterial endophytes interact closely with plant tissues and constitute an essential part of the plant microbiome. These interactions can promote plant growth and elicit specific defense responses against abiotic stresses and pathogen attacks. In this paper, we review the role of endophytic bacteria in modulating defenses of the host rendering the entire plant more resistant to pathogens and pests. The endophyte-induced resistance will probably introduce a new factor when consid-ering plant-pathogen interactions. The impact of the bacterial endosymbionts on the host leading to the priming state is also discussed since it confers a specific adaptation of the plant to the biotic threat.


2021 ◽  
Author(s):  
Ying-Lan Chen ◽  
Fan-Wei Lin ◽  
Kai-Tan Cheng ◽  
Hung-Yu Wang ◽  
Thomas Efferth ◽  
...  

Abstract Proteolytic activation of cytokines regulates immunity in diverse organisms. In animals, cysteine-dependent aspartate-specific proteases (caspases) play central roles in cytokine maturation. Although the proteolytic production of peptide cytokines is also essential for plant immunity, evidence for a plant caspase is still lacking. In this study, we discovered that proteolysis of a caspase-like substrate motif “CNYD” within Pathogenesis-related protein 1 (AtPR1) in Arabidopsis generates an immunomodulatory cytokine (AtCAPE9). Salicylic acid enhances CNYD-targeted protease activity and the proteolytic release of AtCAPE9 from AtPR1 in Arabidopsis. We show that this process involves a caspase, identified as Xylem cysteine peptidase 1 (XCP1). XCP1 exhibits a calcium-modulated pH-activity profile and a comparable activity to human caspases. XCP1 is required to induce systemic immunity triggered by pathogen-associated molecular patterns. This work reveals XCP1 as the first known plant caspase, which produces the cytokine AtCAPE9 from the canonical salicylic acid signaling marker PR1 to activate systemic immunity.


2019 ◽  
Vol 70 (20) ◽  
pp. 5943-5958 ◽  
Author(s):  
Jianlong Zhao ◽  
Lijuan Li ◽  
Qian Liu ◽  
Pei Liu ◽  
Shuang Li ◽  
...  

The plant-parasitic nematode Meloidogyne incognita secretes MIF-like proteins into plant tissues, and MiMIF-2 interacts with two plant annexins to suppress plant immune responses and promote parasitism.


Genes ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 1007
Author(s):  
Divya Kattupalli ◽  
Asha Sreenivasan ◽  
Eppurathu Vasudevan Soniya

Black pepper (Piper nigrum L.) is a prominent spice that is an indispensable ingredient in cuisine and traditional medicine. Phytophthora capsici, the causative agent of footrot disease, causes a drastic constraint in P. nigrum cultivation and productivity. To counterattack various biotic and abiotic stresses, plants employ a broad array of mechanisms that includes the accumulation of pathogenesis-related (PR) proteins. Through a genome-wide survey, eleven PR-1 genes that belong to a CAP superfamily protein with a caveolin-binding motif (CBM) and a CAP-derived peptide (CAPE) were identified from P. nigrum. Despite the critical functional domains, PnPR-1 homologs differ in their signal peptide motifs and core amino acid composition in the functional protein domains. The conserved motifs of PnPR-1 proteins were identified using MEME. Most of the PnPR-1 proteins were basic in nature. Secondary and 3D structure analyses of the PnPR-1 proteins were also predicted, which may be linked to a functional role in P. nigrum. The GO and KEGG functional annotations predicted their function in the defense responses of plant-pathogen interactions. Furthermore, a transcriptome-assisted FPKM analysis revealed PnPR-1 genes mapped to the P. nigrum-P. capsici interaction pathway. An altered expression pattern was detected for PnPR-1 transcripts among which a significant upregulation was noted for basic PnPR-1 genes such as CL10113.C1 and Unigene17664. The drastic variation in the transcript levels of CL10113.C1 was further validated through qRT-PCR and it showed a significant upregulation in infected leaf samples compared with the control. A subsequent analysis revealed the structural details, phylogenetic relationships, conserved sequence motifs and critical cis-regulatory elements of PnPR-1 genes. This is the first genome-wide study that identified the role of PR-1 genes during P. nigrum-P. capsici interactions. The detailed in silico experimental analysis revealed the vital role of PnPR-1 genes in regulating the first layer of defense towards a P. capsici infection in Panniyur-1 plants.


2005 ◽  
Vol 24 (4) ◽  
pp. 216-224 ◽  
Author(s):  
Sujon Sarowar ◽  
Young Jin Kim ◽  
Eui Nam Kim ◽  
Ki Deok Kim ◽  
Byung Kook Hwang ◽  
...  

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