A 2025 Nature Communications study investigated mobile mRNAs in cucumber grafted onto pumpkin rootstock and identified CmoKARI1 as a key root-to-shoot transcript induced during early chilling stress.
Chilling triggered upward movement of a pumpkin transcript
Cucumber/pumpkin heterografts were analyzed under 4°C chilling. Pumpkin-derived mobile transcripts moved into the cucumber scion, with CmoKARI1 emerging as a key early-chilling candidate. The cucumber homolog CsaKARI1 did not show the same long-distance mobility, suggesting transport specificity rather than simple expression abundance.
CmoKARI1 connected isoleucine metabolism to JA-Ile signaling
KARI1 participates in branched-chain amino-acid biosynthesis. CmoKARI1 overexpression increased isoleucine, which was then used to form bioactive jasmonate-isoleucine (JA-Ile). Genetic and metabolic tests supported a CmoKARI1 → Ile → JA-Ile pathway that contributes to chilling tolerance. CmoKARI1 overexpression also improved chilling tolerance in Arabidopsis.
Exogenous 300 µM L-isoleucine improved early chilling tolerance in cucumber, whereas L-valine did not reproduce the protective effect under the tested condition.
The previous article included a claim that CmoKARI1 reached about 10% of all leaf mRNA; that figure is not retained because it is not a supported headline result of the paper.
This study opens a route to thinking about rootstocks as sources of mobile molecular signals, but it does not yet provide a general programmable mRNA-delivery rootstock technology. Mobility rules, graft combinations and field yield/quality effects still need testing.
For related context, see Why Plants Can Survive Below Freezing: Supercooling, Ice Nucleation and Extracellular Freezing.
For related context, see What Controls Cucumber Pedicel Length? An EMS Mutant Points to Cytokinin-Dependent Cell Number.
For related context, see Tomato HY5 Links Light, Electrical Signaling and a Jasmonate Burst During Root-Knot Nematode Defense.
For related context, see Rorippa aquatica Changes Leaf Shape Underwater: Ethylene Drives Heterophylly and Blue Light Attenuates It.
Reference
- Zhang M et al. Root-to-shoot mobile mRNA CmoKARI1 promotes JA-Ile biosynthesis to confer chilling tolerance in grafted cucumbers. Nature Communications. 2025;16:7782. https://doi.org/10.1038/s41467-025-63228-1
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