Ectopic expression of ORANGE promotes carotenoid accumulation and fruit development in tomato

Authors: YAZDANI, MOHAMMAD - Cornell University; SUN, ZHAOXIA - Cornell University; YUAN, HUI - Cornell University; ZENG, SHAOHUA - Cornell University; Thannhauser, Theodore - Ted; VREBALOV, JULIA - Boyce Thompson Institute; MA, QIYUE - Boyce Thompson Institute; XU, YIMIN - Boyce Thompson Institute; FEI, ZHANGJUN - Boyce Thompson Institute; VAN ECK, JOYCE - Boyce Thompson Institute; TIAN, SHIPING - Chinese Academy Of Sciences; TADMOR, YAAKOV - Agricultural Research Organization Of Israel; Giovannoni, James; Li, Li

Submitted to: Plant Biotechnology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/28/2018
Publication Date: 5/15/2018
Citation: Yazdani, M., Sun, Z., Yuan, H., Zeng, S., Thannhauser, T.W., Vrebalov, J., Ma, Q., Xu, Y., Fei, Z., Van Eck, J., Tian, S., Tadmor, Y., Giovannoni, J.J., Li, L. 2018. Ectopic expression of ORANGE promotes carotenoid accumulation and fruit development in tomato. Plant Biotechnology Journal. https://doi.org/10.1111/pbi.12945.
DOI: https://doi.org/10.1111/pbi.12945

Interpretive Summary: Carotenoids are critically important to human nutrition and health. The ORANGE (OR) gene is a key regulator for carotenoid accumulation, but its physiological roles in crops are still not very clear. In this study, we provide new information for the novel roles of OR in mediating carotenoid biosynthesis, plastid development, and fruit development. We discover that in addition to regulating carotenoid accumulation in low carotenoid-containing tissues, OR also greatly enhances carotenoid levels in tomato fruit tissues that are already enriched with carotenoids. Moreover, OR was found to promote early flowering and fruit set, two important agronomic traits for fruit production. These results provide evidence for a broad application of OR in engineering crops not only for carotenoid nutritional quality improvement, but also for fruit production.

Technical Abstract: Carotenoids are critically important to plants and humans. The ORANGE (OR) gene is a key regulator for carotenoid accumulation, but its physiological roles in crops remain elusive. In this study, we generated transgenic tomato ectopically overexpressing the Arabidopsis wild type OR (AtORWT) and a 'golden SNP'-containing OR (AtORHis). We found that AtORHis initiated chromoplast formation in very young fruit and stimulated carotenoid accumulation at all fruit developmental stages, uncoupled from other ripening activities. The elevated levels of carotenoids in the AtOR lines were distributed in the same sub-plastidial fractions as in wild type tomato, indicating an adaptive response of plastids to sequester the increased carotenoids. Microscopic analysis revealed that the plastid sizes were increased in both AtORWT and AtORHis lines at early fruit developmental stages. Moreover, AtOR overexpression promoted early flowering, fruit set, and seed production. Ethylene production and the expression of ripening-associated genes were also significantly increased in the AtOR transgenic fruit at ripening stages. RNA-Seq transcriptomic profiling highlighted the primary effects of OR overexpression on the genes in the processes related to RNA, protein, and signalling in tomato fruit. Taken together, these results expand our understanding of OR in mediating carotenoid accumulation in plants and suggest additional roles of OR in affecting plastid size as well as flower and fruit development, thus making OR a target gene not only for nutritional biofortification of agricultural products but also for alteration of horticultural traits.