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TcNPR3 from Theobroma cacao functions as a repressor of the pathogen defense response.

ABSTRACT: BACKGROUND: Arabidopsis thaliana (Arabidopsis) NON-EXPRESSOR OF PR1 (NPR1) is a transcription coactivator that plays a central role in regulating the transcriptional response to plant pathogens. Developing flowers of homozygous npr3 mutants are dramatically more resistant to infection by the pathogenic bacterium Pseudomonas syringae, suggesting a role of NPR3 as a repressor of NPR1-mediated defense response with a novel role in flower development. RESULTS: We report here the characterization of a putative NPR3 gene from the tropical tree species Theobroma cacao (TcNPR3). Like in Arabidopsis, TcNPR3 was constitutively expressed across a wide range of tissue types and developmental stages but with some differences in relative levels compared to Arabidopsis. To test the function of TcNPR3, we performed transgenic complementation analysis by introducing a constitutively expressing putative TcNPR3 transgene into an Arabidopsis npr3 mutant. TcNPR3 expressing Arabidopsis plants were partially restored to the WT pathogen phenotype (immature flowers susceptible to bacterial infection). To test TcNPR3 function directly in cacao tissues, a synthetic microRNA targeting TcNPR3 mRNA was transiently expressed in cacao leaves using an Agrobacterium-infiltration method. TcNPR3 knock down leaf tissues were dramatically more resistance to infection with Phytophthora capsici in a leaf bioassay, showing smaller lesion sizes and reduced pathogen replication. CONCLUSIONS: We conclude that TcNPR3 functions similar to the Arabidopsis NPR3 gene in the regulation of the cacao defense response. Since TcNPR3 did not show a perfect complementation of the Arabidopsis NPR3 mutation, the possibility remains that other functions of TcNPR3 remain to be found. This novel knowledge can contribute to the breeding of resistant cacao varieties against pathogens through molecular markers based approaches or biotechnological strategies.

SUBMITTER: Shi Z

PROVIDER: S-EPMC3878973 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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TcNPR3 from Theobroma cacao functions as a repressor of the pathogen defense response.

Shi Zi Z Zhang Yufan Y Maximova Siela N SN Guiltinan Mark J MJ

BMC plant biology 20131206

<h4>Background</h4>Arabidopsis thaliana (Arabidopsis) NON-EXPRESSOR OF PR1 (NPR1) is a transcription coactivator that plays a central role in regulating the transcriptional response to plant pathogens. Developing flowers of homozygous npr3 mutants are dramatically more resistant to infection by the pathogenic bacterium Pseudomonas syringae, suggesting a role of NPR3 as a repressor of NPR1-mediated defense response with a novel role in flower development.<h4>Results</h4>We report here the charact ...[more]

PMID: 24314063

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Project description:BackgroundThe pathogenesis-related (PR) group of proteins are operationally defined as polypeptides that increase in concentration in plant tissues upon contact with a pathogen. To date, 17 classes of highly divergent proteins have been described that act through multiple mechanisms of pathogen resistance. Characterizing these families in cacao, an economically important tree crop, and comparing the families to those in other species, is an important step in understanding cacao's immune response.ResultsUsing publically available resources, all members of the 17 recognized pathogenesis-related gene families in the genome of Theobroma cacao were identified and annotated resulting in a set of ~350 members in both published cacao genomes. Approximately 50 % of these genes are organized in tandem arrays scattered throughout the genome. This feature was observed in five additional plant taxa (three dicots and two monocots), suggesting that tandem duplication has played an important role in the evolution of the PR genes in higher plants. Expression profiling captured the dynamics and complexity of PR genes expression at basal levels and after induction by two cacao pathogens (the oomycete, Phytophthora palmivora, and the fungus, Colletotrichum theobromicola), identifying specific genes within families that are more responsive to pathogen challenge. Subsequent qRT-PCR validated the induction of several PR-1, PR-3, PR-4, and PR-10 family members, with greater than 1000 fold induction detected for specific genes.ConclusionsWe describe candidate genes that are likely to be involved in cacao's defense against Phytophthora and Colletotrichum infection and could be potentially useful for marker-assisted selection for breeding of disease resistant cacao varieties. The data presented here, along with existing cacao-omics resources, will enable targeted functional genetic screening of defense genes likely to play critical functions in cacao's defense against its pathogens.

Dataset Information

TcNPR3 from Theobroma cacao functions as a repressor of the pathogen defense response.

Publications

TcNPR3 from Theobroma cacao functions as a repressor of the pathogen defense response.

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