The chloroplast-localised transporter RETICULATA controls palisade mesophyll cell division and expansion

Loss of function of the chloroplast amino acid transporter RETICULATA in the reticulata-6 (re-6) mutant enlarges leaf intercellular air spaces specifically by increasing palisade mesophyll expansion.

• Why it matters: Leaf air space patterning is important for photosynthesis and water use, yet the molecular mechanism linking chloroplast dysfunction to larger air spaces has been unclear for decades.
• What they did: The study characterized air space morphogenesis in RETICULATA mutants and tested whether changes reflected programmed cell death, stomatal density, or mesophyll cell identity, then quantified palisade cell division and morphology.
• The result: RETICULATA is linked to palisade mesophyll morphogenesis by promoting early palisade cell division and suppressing later cell expansion, implying chloroplasts may regulate air space patterning in response to light.

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