Yoram Eyal | Search PubMed

PubMed2025

In planta genome editing in citrus facilitated by co-expression of CRISPR/Cas and developmental regulators.

Recent advances in the field of genome editing offer a promising avenue for targeted trait improvements in fruit trees. However, the predominant method taken for genome editing in citrus (and other fruit trees) involves the time-consuming tissue culture approach, thereby prolonging the overall citrus breeding process and subjecting it to the drawbacks associated with somaclonal variation. In this study, we introduce an in planta approach for genome editing in soil-grown citrus plants via direct transformation of young seedlings. Our editing system, abbreviated here as IPGEC (in planta genome editing in citrus), is designed to transiently co-express three key gene groups in citrus tissue via Agrobacterium tumefaciens: (i) a genome-editing catalytic group, (ii) a shoot induction and regeneration group, and (iii) a T-DNA enhanced delivery group. This integrated system significantly improves de novo shoot induction and regeneration efficiency of edited tissue. By incorporating single-guides RNA's (sgRNA's) targeting the carotenoid biosynthetic gene PHYTOENE DESATURASE (CsPDS), the IPGEC system effectively produced mutated albino shoots, confirming its ability to generate homozygous/biallelic genome-edited plants. By using high throughput screening, we provide evidence that transgene-free genome-edited plants could be obtained following the IPGEC approach. Our findings further suggest that the efficiency of specific developmental regulators in inducing transformation and regeneration rates may be cultivar-specific and therefore needs to be optimized per cultivar. Finally, targeted breeding for specific trait improvements in already successful cultivars is likely to revolutionize fruit tree breeding and will pave the way for accelerating the development of high-quality citrus cultivars.

Citrus↗

PubMed2025

Targeting the "bitterness gene" by genome editing abolishes synthesis of bitter flavanones in citrus; prospects for new varieties and extended climates for cultivation.

Bitterness in citrus fruit is conferred by flavanone-neohesperidosides, whose accumulation is catalyzed by a single enzyme flavanone-7-O-glucosides-1,2-rhamnosyltransferase (1,2RhaT), expressed in both leaves and fruit. To eliminate citrus bitterness, we used CRISPR/Cas9 genome editing to inactivate the 1,2RhaT gene in grapefruit (Citrus paradisi) and "Carrizo" citrange (Citrus sinensis × Citrus trifoliata). Edited lines displayed frameshift mutations that introduced premature stop codons, effectively abolishing the synthesis of the bitter neohesperidosides naringin, neohesperidin, and poncirin. Metabolomic analyses in leaves from 1,2RhaT-mutant lines confirmed the absence of bitter flavanone-neohesperidosides and a compensatory increase in the tasteless flavanone-rutinosides hesperidin, didymin, and narirutin. Since 1,2RhaT is encoded by a single gene, our findings in leaves are expected to be identical for fruit and thus demonstrate a strategy for developing non-bitter citrus cultivars while retaining health-benefitting flavonoid levels. Furthermore, cold-hardy citrus species that are currently unacceptably bitter due to high flavanone-neohesperidoside levels may become useful sources for introduction of cold-hardiness following inactivation of the 1,2RhaT gene. This approach thus paves the way for expanding grapefruit markets and breeding cold-hardy, palatable citrus varieties that are better suited to a wider range of climates.

Flavanones↗