Ornacitrus: Development of Genetically Modified Anthocyanin-expressing Citrus with Both Ornamental and Fresh Fruit Potential

摘要

Anthocyanins are beneficial bioflavonoids that have numerous roles in human health maintenance, disease prevention, and overall well-being. In addition, anthocyanins are key to the consumer appeal of many ornamental plants. Most Citrus (Citrus L.) plants do not produce anthocyanins under warm tropical and subtropical. conditions. Anthocyanin pigments, responsible for the "blood" color of blood orange [Citrus sinensis (L.) Osbeck], are produced after exposure to cold conditions during the fruit's development. The transcription factor Ruby is responsible for the production of anthocyanin in blood orange. Functionally, similar genes exist in other fruit crops such as grape [Vitis vinifera L. (VvmybA1 and VvmybA2)] and apple [Malus xdomestica Borkh (MdMYB10)]. Here, VvmybA1 and Ruby genes were constitutively expressed in 'Mexican' lime (Citrus aurantifolia Swingle). This cultivar performs optimally under Florida's humid subtropical environment and has a short juvenile phase. Constitutive expression of VvmybA1 or Ruby resulted in anthocyanin pigmentation in the leaves, stems, flowers, and fruit. An increased pigmentation of the outer layer(s) of stem tissue was observed in 'Mexican' lime overexpressing the VvmybA1, whereas lower anthocyanin levels were observed in plants overexpressing Ruby. Enhanced pigmentation was also observed in the young leaves; however, pigment intensity levels decreased as the leaves matured. Flower color ranged from light pink to fuchsia and the fruit pulp of several 'Mexican' lime lines were maroon; similar to a blood orange. The results demonstrate that expression of anthocyanin-related genes can affect temporal pigmentation patterns in citrus. It also opens up the possibility for the development of modified blood orange and other cultivars adapted to the subtropical environment.