Tissue-specific expression of Ruby in Mexican lime (C. aurantifolia) confers anthocyanin accumulation in fruit

Authors: Thilmony, Roger; DASGUPTA, KASTURI - Former ARS Employee; SHAO, MIN - Volunteer; HARRIS, DAREN - Former ARS Employee; HARTMAN, JAKE - Former ARS Employee; Harden, Leslie - Les; Chan, Ronald; Thomson, James - Jim

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/19/2022
Publication Date: 8/8/2022
Citation: Thilmony, R.L., Dasgupta, K., Shao, M., Harris, D., Hartman, J., Harden, L.A., Chan, R., Thomson, J.G. 2022. Tissue-specific expression of Ruby in Mexican lime (C. aurantifolia) confers anthocyanin accumulation in fruit. Frontiers in Plant Science. 13. Article 945738. https://doi.org/10.3389/fpls.2022.945738.
DOI: https://doi.org/10.3389/fpls.2022.945738

Interpretive Summary: This work reports testing of fruit specific promoters in Mexican Lime. Three promoters were isolated from citrus and one from plum. Results demonstrate that the promoter CitWax has for high preferential expression, where it shows strong activity in the fruit (juice sac) and weak activity in floral tissues and undetectable activity in other tissues. The CitWax promoter opens the possibility of citrus fruit as dedicated biofactories for proteins or metabolites of choice.

Technical Abstract: Tissue specific promoters are important tools for precise genetic engineering of crop plants. Four previously characterized novel fruit-specific/preferential promoters that provide enhanced fruit quality traits have been identified and are under investigation in Mexican Lime. Among the four candidate promoters characterized in this study, the CitWAX promoter exhibited high fruit-preferential expression with strong activity in the juice sac of fruit, moderate activity in floral tissues, and undetectable activity in other tissues. In plants with high levels of detectable anthocyanin expression in juvenile leaves was occasionally observed but the color disappeared as the leaf matured. The CitVO1, CitUNK, E8 and PamMybA promoters, while previously exhibiting strong fruit-preferential expression in tomato showed no detectable activity in any citrus tissue. The overexpression of CsmybA1 in citrus could increase the nutritional values and the health benefits of their fruits while the CitWAX promoter could be used to specifically expression other traits of interest.