Abstract :
[en] Plant pathogens cause significant crop damages and yield losses each year. Rice bacterial blight and rice blast have the most dominant and destructive effects on rice production and quality. In plants, genes encoding valine glutamine (VQ)-motif containing proteins play an important role in plant defense responses. The objectives of this thesis are (1) to summarize the sequence and evolutionary characteristics, as well as roles and working mechanisms of VQ genes in plants, (2) to explore new VQ genes for rice resistance to diseases or pests, (3) generate novel germplasm resistant to rice bacterial blight and rice blast through CRISPR/Cas9, and (4) analyze the potential underlying mechanisms.
We reviewed the research progress of plant VQ family genes. The VQ family genes were successively identified in various plant species and found to be up- or down-regulated when exposed to environmental stress, pathogen invasion, and phytohormone treatment. They participate in various biological processes and responses to biotic or abiotic stress. VQ proteins function as important transcription regulators via interacting with WRKY transcription factors (WRKY), Mitogen-activated protein kinases (MAPK), and other proteins. Here, we summarized the detailed molecular characteristics, biological functions, and working mechanisms of published VQ proteins in plants.
In order to provide more detailed information on VQ family genes in plants, a total of 2469 VQ genes were identified from 56 plant species, including bryophytes, gymnosperms, and angiosperms. A comprehensive bioinformatics analysis, including conserved motifs, basic molecular characterization, and systemic clustering was carried out. Importantly, the research on the VQ family genes in gymnosperms has not been reported yet. So, we selected Ginkgo biloba, Taxus chinensis and Pinus tabuliformis as target species, identified their VQ gene members, and analyzed their molecular features, gene structure, subcellular location, chromosome distribution, duplication events, expression levels, synteny blocks, and evolutionary comparisons.
The CRISPR/Cas9 technology has been widely applied in plant genome editing and crop improvement. Here, we report that a rice valine-glutamine (VQ) motif-containing protein, OsVQ25, balances broad-spectrum disease resistance and plant growth by interacting with a U-Box E3 ligase, OsPUB73, and a transcription factor, OsWRKY53. OsPUB73 was found to positively regulate rice resistance against Magnaporthe oryzae and Xanthomonas oryzae by interacting with and promoting OsVQ25 degradation via the 26S proteasome pathway. Knockout mutants of OsVQ25 exhibited enhanced resistance to both pathogens without growth and yield penalty. Furthermore, OsVQ25 interacted with and suppressed the transcriptional activity of OsWRKY53, a positive regulator of plant immunity. OsWRKY53 downstream defense-related genes and brassinosteroid signaling genes were upregulated in osvq25 mutants. Our findings revealed a OsPUB73-OsVQ25-OsWRKY53 module that finetunes plant immunity and growth at the transcriptional and posttranslational levels.
In conclusion, we have reviewed and summarized the characteristics, functions, and working mechanisms of VQ family genes in plants, and engineered novel resistant rice germplasms through CRISPR/Cas9-mediated genome editing technology and further revealed their disease resistance mechanisms.
