MicroRNA switch controls how readily lettuce regrows new shoots

Scientists have identified a genetic module that helps determine how easily lettuce can regenerate entire shoots from tissue in the lab, a trait that directly influences the success of plant transformation and genome editing. The study, published in Plant Cell Reports, points to the microRNA miR319 and one of its targets, the gene LsTCP4, as key players in controlling regenerative competence in this important horticultural crop.

The research team began with a genome-wide survey of the TEOSINTE BRANCHED1/CYCLOIDEA/PROLIFERATING CELL FACTOR, or TCP, gene family in lettuce (Lactuca sativa). They identified thirty-three LsTCP genes and sorted them into three groups: Class I/PCF, Class II/CIN, and Class II/CYC/TB1. Five of the CIN-class genes, LsTCP2, LsTCP3, LsTCP4, LsTCP10 and LsTCP24, were predicted to be high-confidence targets of miR319, and degradome sequencing provided evidence that miR319 guides the cleavage of these transcripts.

To test what this module does during regeneration, the researchers manipulated miR319 levels in lettuce explants. When MIR319 was overexpressed, the explants regenerated far more readily than wild type: regeneration efficiency rose by 67.3 percent and the number of shoots produced increased by 79.4 percent. Conversely, when miR319 was suppressed using a STTM-based approach, regeneration efficiency fell by 49.6 percent and shoot production dropped by 66.4 percent.

These opposing phenotypes were accompanied by altered expression of several miR319-targeted CIN-TCP genes, with LsTCP4, LsTCP10 and LsTCP24 standing out as particularly responsive. The pattern suggested that miR319 promotes regeneration by reducing the activity of one or more of these transcription factor genes.

To pinpoint which target matters most, the team disrupted individual genes. Knocking out LsTCP4 increased regeneration efficiency by 61.8 percent and shoot production by 91.6 percent relative to wild type, closely mimicking the effect of miR319 overexpression. In contrast, disrupting LsTCP17, a CIN-class gene that is not a miR319 target, had no significant effect on regeneration under the conditions tested.

Together, these results support LsTCP4 as a major miR319-responsive negative regulator of de novo shoot regeneration in lettuce. In other words, when LsTCP4 is active it restrains regeneration, and when miR319 clears it away, explants become more competent to form new shoots.

The findings carry practical weight because regeneration is a major bottleneck for crop improvement. Transformation and genome-editing efficiency depend heavily on how readily plant tissue can rebuild organs, and the endogenous regulatory networks governing this ability in horticultural crops have remained incompletely understood. The study’s authors note that regeneration is a major determinant of transformation and genome-editing efficiency, which is why identifying the networks behind regenerative competence matters for lettuce improvement.

The miR319–TCP module is already known to regulate multiple developmental processes in plants, but its role in lettuce regeneration had not previously been defined. This study extends the module’s known functions into the realm of regenerative competence, linking a well-characterized microRNA family to a trait of direct biotechnological value in this crop.

As with any study of this kind, the results come from laboratory tissue-culture conditions in a single species, and the reported percentages reflect the specific experimental systems used. The authors note that the findings suggest, rather than prove, the broader role of the miR319–LsTCP4 module in regenerative competence, and further work will be needed to translate the discovery into practical breeding or editing pipelines. Even so, the identification of a clear negative regulator offers a concrete genetic handle for researchers seeking to make lettuce more amenable to modern genome engineering.

Subject of Research: The miR319–LsTCP4 module regulates de novo shoot regeneration in lettuce

Article Title: The miR319–LsTCP4 module regulates de novo shoot regeneration in lettuce

Article References: Jiang, T., Tanwir, S. E., Karn, A., Liu, F., & Huo, H. (2026). The miR319–LsTCP4 module regulates de novo shoot regeneration in lettuce. Plant Cell Reports, 45(11), Article 341. https://doi.org/10.1007/s00299-026-04001-6

Image Credits: AI Generated

DOI: 10.1007/s00299-026-04001-6

Keywords: miR319, LsTCP4, module, regulates, novo, shoot, regeneration, lettuce, scientific research