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Adaptation of the metabolomics profile of rice after Pyricularia oryzae infection

Azizi P, Osman M, Hanafi MM, Sahebi M, Yusop MR, Taheri S

Plant Physiol Biochem, 2019 Nov;144:466-479.
PMID: 31655345 DOI: 10.1016/j.plaphy.2019.10.014

Pyricularia oryzae (P. oryzae), one of the most devastating fungal pathogens, is the cause of blast disease in rice. Infection with a blast fungus induces biological responses in the host plant that lead to its survival through the termination or suppression of pathogen growth, and metabolite compounds play vital roles in plant interactions with a wide variety of other organisms. Numerous studies have indicated that rice has a multi-layered plant immune system that includes pre-developed (e.g., cell wall and phytoanticipins), constitutive and inducible (phytoalexins) defence barriers against stresses. Significant progress towards understanding the basis of the molecular mechanisms underlying the defence responses of rice to P. oryzae has been achieved. Nonetheless, even though the important metabolites in the responses of rice to pathogens have been identified, their exact mechanisms and their contributions to plant immunity against blast fungi have not been elucidated. The purpose of this review is to summarize and discuss recent advances towards the understanding of the integrated metabolite variations in rice after P. oryzae invasion.

Matched MeSH terms: Plant Immunity
Fulltext CaWRKY30 Positively Regulates Pepper Immunity by Targeting CaWRKY40 against Ralstonia solanacearum Inoculation through Modulating Defense-Related Genes

Hussain A, Khan MI, Albaqami M, Mahpara S, Noorka IR, Ahmed MAA, et al.

Int J Mol Sci, 2021 Nov 08;22(21).
PMID: 34769521 DOI: 10.3390/ijms222112091

The WRKY transcription factors (TFs) network is composed of WRKY TFs' subset, which performs a critical role in immunity regulation of plants. However, functions of WRKY TFs' network remain unclear, particularly in non-model plants such as pepper (Capsicum annuum L.). This study functionally characterized CaWRKY30-a member of group III Pepper WRKY protein-for immunity of pepper against Ralstonia solanacearum infection. The CaWRKY30 was detected in nucleus, and its transcriptional expression levels were significantly upregulated by R. solanacearum inoculation (RSI), and foliar application ethylene (ET), abscisic acid (ABA), and salicylic acid (SA). Virus induced gene silencing (VIGS) of CaWRKY30 amplified pepper's vulnerability to RSI. Additionally, the silencing of CaWRKY30 by VIGS compromised HR-like cell death triggered by RSI and downregulated defense-associated marker genes, like CaPR1, CaNPR1, CaDEF1, CaABR1, CaHIR1, and CaWRKY40. Conversely, transient over-expression of CaWRKY30 in pepper leaves instigated HR-like cell death and upregulated defense-related maker genes. Furthermore, transient over-expression of CaWRKY30 upregulated transcriptional levels of CaWRKY6, CaWRKY22, CaWRKY27, and CaWRKY40. On the other hand, transient over-expression of CaWRKY6, CaWRKY22, CaWRKY27, and CaWRKY40 upregulated transcriptional expression levels of CaWRKY30. The results recommend that newly characterized CaWRKY30 positively regulates pepper's immunity against Ralstonia attack, which is governed by synergistically mediated signaling by phytohormones like ET, ABA, and SA, and transcriptionally assimilating into WRKY TFs networks, consisting of CaWRKY6, CaWRKY22, CaWRKY27, and CaWRKY40. Collectively, our data will facilitate to explicate the underlying mechanism of crosstalk between pepper's immunity and response to RSI.

Matched MeSH terms: Plant Immunity/drug effects; Plant Immunity/immunology*
Fulltext EgJUB1 and EgERF113 transcription factors as potential master regulators of defense response in Elaeis guineensis against the hemibiotrophic Ganoderma boninense

Sakeh NM, Abdullah SNA, Bahari MNA, Azzeme AM, Shaharuddin NA, Idris AS

BMC Plant Biol, 2021 Jan 22;21(1):59.
PMID: 33482731 DOI: 10.1186/s12870-020-02812-7

BACKGROUND: Hemibiotrophic pathogen such as the fungal pathogen Ganoderma boninense that is destructive to oil palm, manipulates host defense mechanism by strategically switching from biotrophic to necrotrophic phase. Our previous study revealed two distinguishable expression profiles of oil palm genes that formed the basis in deducing biotrophic phase at early interaction which switched to necrotrophic phase at a later stage of infection.
RESULTS: The present report is a continuing study from our previous published transcriptomic profiling of oil palm seedlings against G. boninense. We focused on identifying differentially expressed genes (DEGs) encoding transcription factors (TFs) from the same RNA-seq data; resulting in 106 upregulated and 108 downregulated TFs being identified. The DEGs are involved in four established defense-related pathways responsible for cell wall modification, reactive oxygen species (ROS)-mediated signaling, programmed cell death (PCD) and plant innate immunity. We discovered upregulation of JUNGBRUNNEN 1 (EgJUB1) during the fungal biotrophic phase while Ethylene Responsive Factor 113 (EgERF113) demonstrated prominent upregulation when the palm switches to defense against necrotrophic phase. EgJUB1 was shown to have a binding activity to a 19 bp palindromic SNBE1 element, WNNYBTNNNNNNNAMGNHW found in the promoter region of co-expressing EgHSFC-2b. Further in silico analysis of promoter regions revealed co-expression of EgJUB1 with TFs containing SNBE1 element with single nucleotide change at either the 5th or 18th position. Meanwhile, EgERF113 binds to both GCC and DRE/CRT elements promoting plasticity in upregulating the downstream defense-related genes. Both TFs were proven to be nuclear-localized based on subcellular localization experiment using onion epidermal cells.
CONCLUSION: Our findings demonstrated unprecedented transcriptional reprogramming of specific TFs potentially to enable regulation of a specific set of genes during different infection phases of this hemibiotrophic fungal pathogen. The results propose the intricacy of oil palm defense response in orchestrating EgJUB1 during biotrophic and EgERF113 during the subsequent transition to the necrotrophic phase. Binding of EgJUB1 to SNBE motif instead of NACBS while EgERF113 to GCC-box and DRE/CRT motifs is unconventional and not normally associated with pathogen infection. Identification of these phase-specific oil palm TFs is important in designing strategies to tackle or attenuate the progress of infection.

Matched MeSH terms: Plant Immunity/immunology*
Sequence analysis and gene expression of putative exo- and endo-glucanases from oil palm (Elaeis guineensis) during fungal infection

Yeoh KA, Othman A, Meon S, Abdullah F, Ho CL

J Plant Physiol, 2012 Oct 15;169(15):1565-70.
PMID: 22854183 DOI: 10.1016/j.jplph.2012.07.006

Glucanases are enzymes that hydrolyze a variety β-d-glucosidic linkages. Plant β-1,3-glucanases are able to degrade fungal cell walls; and promote the release of cell-wall derived fungal elicitors. In this study, three full-length cDNA sequences encoding oil palm (Elaeis guineensis) glucanases were analyzed. Sequence analyses of the cDNA sequences suggested that EgGlc1-1 is a putative β-d-glucan exohydolase belonging to glycosyl hydrolase (GH) family 3 while EgGlc5-1 and EgGlc5-2 are putative glucan endo-1,3-β-glucosidases belonging to GH family 17. The transcript abundance of these genes in the roots and leaves of oil palm seedlings treated with Ganoderma boninense and Trichoderma harzianum was profiled to investigate the involvement of these glucanases in oil palm during fungal infection. The gene expression of EgGlc1-1 in the root of oil palm seedlings was increased by T. harzianum but suppressed by G. boninense; while the gene expression of both EgGlc5-1 and EgGlc5-2 in the roots of oil palm seedlings was suppressed by G. boninense or/and T. harzianum.

Matched MeSH terms: Plant Immunity/genetics*
Expression of rice thaumatin-like protein gene in transgenic banana plants enhances resistance to fusarium wilt

Mahdavi F, Sariah M, Maziah M

Appl Biochem Biotechnol, 2012 Feb;166(4):1008-19.
PMID: 22183565 DOI: 10.1007/s12010-011-9489-3

The possibility of controlling Fusarium wilt--caused by Fusarium oxysporum sp. cubensec (race 4)--was investigated by genetic engineering of banana plants for constitutive expression of rice thaumatin-like protein (tlp) gene. Transgene was introduced to cauliflower-like bodies' cluster, induced from meristemic parts of male inflorescences, using particle bombardment with plasmid carrying a rice tlp gene driving by the CaMV 35S promoter. Hygromycin B was used as the selection reagent. The presence and integration of rice tlp gene in genomic DNA confirmed by PCR and Southern blot analyses. RT-PCR revealed the expression of transgene in leaf and root tissues in transformants. Bioassay of transgenic banana plants challenged with Fusarium wilt pathogen showed that expression of TLP enhanced resistance to F. oxysporum sp. cubensec (race 4) compared to control plants.

Matched MeSH terms: Plant Immunity
The PAL2 promoter activities in relation to structural development and adaptation in Arabidopsis thaliana

Wong JH, Namasivayam P, Abdullah MP

Planta, 2012 Feb;235(2):267-77.
PMID: 21874349 DOI: 10.1007/s00425-011-1506-9

Phenylalanine ammonia lyase (PAL) plays a major role in plant growth, development and adaptation. In Arabidopsis thaliana, the enzyme is encoded by four genes, namely PAL1, PAL2, PAL3, and PAL4 with PAL1 and PAL2 being closely related phylogenetically and functionally. PAL1 promoter activities are associated with plant development and are inducible by various stress agents. However, PAL2 promoter activities have not been functionally analysed. Here, we show that the PAL2 promoter activities are associated with the structural development of a plant and its organs. This function was inducible in an organ-specific manner by the avirulent strain of Pseudomonas syringae pv. tomato (JL1065). The PAL2 promoter was active throughout the course of the plant development particularly in the root, rosette leaf, and inflorescence stem that provide the plant with structural support. In aerial organs, the levels of PAL2 promoter activities were negatively correlated with relative positions of the organs to the rosette leaves. The promoter was inducible in the root following an inoculation by JL1065 in the leaf suggesting PAL2 to be part of an induced defence system. Our results demonstrate how the PAL2 promoter activities are being coordinated and synchronised for the structural development of the plant and its organs based on the developmental programme. Under certain stress conditions the activity may be induced in favour of certain organs.

Matched MeSH terms: Plant Immunity