Manipulation of chloroplast development to enhance photosynthesis and nutritional value of tomato

Abstract

Fruit chloroplasts convert light energy into chemical energy, contributing to fruit growth, development and the overall plant carbon budget. During ripening, the transition from chloroplasts to chromoplasts is associated with chlorophyll degradation and carotenoid accumulation. This study explores a novel strategy to enhance tomato (Solanum lycopersicum) fruit photosynthetic pigment content, photochemical capacity and nutritional value by the genetic manipulation of chloroplast development. Transgenic tomato lines were generated overexpressing BpMADS, a MADS-box gene from birch (Betula platyphylla), under the control of fruit-specific promoters to drive expression at both green and ripening stages. Additional lines were developed with two Arabidopsis thaliana GATA transcription factors, AtCGA1 and AtGNC, involved in chloroplast biogenesis, and a double construct simultaneously overexpressing the plastid division components AtPDV1 and AtPDV2, all driven by early fruit-specific promoters. Overexpression of BpMADS and AtCGA1 significantly enhanced chloroplast coverage, chlorophyll content and photochemical capacity of green tomato fruit. Similarly, overexpression of AtGNC led to enhanced chlorophyll and carotenoid levels in green fruit. Additionally, both early and ripening expression of BpMADS were associated with higher levels of lycopene and β-carotene in red ripe fruits. By contrast, simultaneous overexpression of AtPDV1/PDV2 had a limited effect on fruit photosynthesis. Taken together, the results indicate that the manipulation of chloroplast development via transcription factors can provide a practical route to improve photosynthetic function and nutritional content in tomato fruits. This work provides new insights into the contributions of chloroplast biogenesis to fruit metabolism and could be used in other fruit crops.

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ORCID for Matthew Terry: orcid.org/0000-0001-5002-2708

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