CRISPR-Edited CsLOB1 Promoter Mutations for Citrus Canker Resistance
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Solution Overview
Problem
Citrus canker, caused by Xanthomonas citri subsp. citri, is a devastating disease affecting most commercial citrus varieties, and conventional breeding is hindered by narrow genetic diversity and long juvenile periods, limiting the development of resistant cultivars.
Innovation Solution
The CRISPR/Cas9 system is used to introduce mutations in the PthA4 effector binding elements of the CsLOB1 gene, disrupting the pathogen's ability to induce disease susceptibility, thereby creating transgenic citrus plants resistant to citrus canker.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional breeding is used to develop disease-resistant citrus varieties, then genetic diversity is maintained, but the breeding process takes a long time due to the long juvenile period
Solution Approach 1:
The invention changes the fundamental parameter of how genetic modification is achieved - transitioning from conventional cross-breeding methods to CRISPR/Cas9 genome editing. This allows direct modification of the CsLOB1 gene to create disease-resistant citrus varieties without waiting through multiple generations of breeding, thereby dramatically reducing the time required while maintaining genetic precision.
Solution Approach 2:
The invention performs preliminary action by directly editing the target gene (CsLOB1) in the initial stage, rather than relying on gradual genetic changes through conventional breeding. The CRISPR/Cas9 system introduces specific mutations (such as T→C or T→G transitions) in the effector binding element before plant development completes, allowing disease resistance to be established early in the plant lifecycle.
2Reliability
If conventional breeding is used to develop disease-resistant citrus varieties, then natural genetic variation is preserved, but genetic diversity becomes limited due to narrow breeding pools
Solution Approach 1:
The invention changes the approach to genetic modification by using precise CRISPR/Cas9 editing rather than conventional breeding. This allows introduction of specific resistance traits into diverse citrus genetic backgrounds without being constrained by narrow breeding pools, thereby maintaining adaptability while achieving disease resistance.
3Productivity
If CRISPR/Cas9 is used to edit the CsLOB1 gene, then disease resistance is achieved quickly, but transgenic modification is required
Solution Approach 1:
The invention extracts and modifies only the specific functional element responsible for disease susceptibility - the effector binding element in the CsLOB1 promoter region. By using CRISPR/Cas9 to target and mutate this specific sequence (through T→C or T→G transitions), the invention achieves disease resistance by removing the pathogen recognition site, thereby simplifying the modification process while maintaining high breeding speed.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The approach effectively reduces or abolishes the binding of Xanthomonas spp. PthA4 protein to the CsLOB1 gene promoters, rendering citrus plants resistant to citrus canker infection, as demonstrated by reduced or absent canker symptoms in transgenic plants.
Implementation Method 1
Cas9 can be guided to specific genomic loci by a duplex consisting of mature CRISPR RNA (crRNA) and trans-activating crRNA, where the target DNA is cleaved. The CRISPR-associated Cas9 endonuclease contains the HNH and RuvC nuclease domains, which are responsible for cleavage of both strands of the target DNA.
Implementation Method 2
The CRISPR-associated Cas9 endonuclease contains the HNH and RuvC nuclease domains, which are responsible for cleavage of both strands of the target DNA.
Implementation Method 3
a synthetic single-guide RNA (sgRNA) can guide Cas9 to perform sequence-specific genome editing
Implementation Method 4
PthA4 specifically binds to the effector binding elements (EBEPthA4) in the CsLOB1 promoter region (EBEPthA4-CsLOBP) to activate its gene expression
Data Source
AI summary
The invention pertains to a plant cell or a plant having one or more mutations in the promoters of both the alleles for CsLOB1 gene, wherein the one or more mutations are in the promoter binding sites for PthA4 protein from Xanthomonas spp., and wherein the one or more mutations reduce or abolish the binding of the Xanthomonas spp. PthA4 protein on to the binding sites in the promoters of the CsLOB1 genes. Also, a plant cell or a plant having one or more mutations in the coding regions of both the alleles for CsLOB1 gene, wherein the one or more mutations reduce or abolish the binding of the function of CsLOB1 protein are provided. The invention further pertains to the methods of making the plant cell or the plant resistant to infection by Xanthomonas spp.