Abstract
BackgroundPromoters that confer expression in fruit tissues are important tools for genetic engineering of fruit quality traits, yet few fruit-specific promoters have been identified, particularly for citrus fruit development.ResultsIn this study, we report five citrus fruit-specific/preferential promoters for genetic engineering. Additionally, we have characterized a novel fruit-preferential promoter from plum. Genes specifically expressed in fruit tissues were selected and their isolated promoter regions were fused with the GUSPlus reporter gene for evaluation in transgenic plants. Stable transformation in Micro-Tom tomato demonstrated that the candidate promoter regions exhibit differing levels of expression and with varying degrees of fruit specificity.ConclusionsAmong the five candidate citrus promoters characterized in this study, the CitSEP promoter showed a fruit-specific expression pattern, while the CitWAX and CitJuSac promoters exhibited high fruit-preferential expression with strong activity in the fruit, weak activity in floral tissues and low or undetectable activity in other tissues. The CitVO1, CitUNK and PamMybA promoters, while exhibiting strong fruit-preferential expression, also showed consistent weak but detectable activity in leaves and other vegetative tissues. Use of these fruit specific/preferential promoters for genetic engineering can help with precise expression of beneficial genes and help with accurate prediction of the activity of new genes in host fruit plants.
Highlights
Promoters that confer expression in fruit tissues are important tools for genetic engineering of fruit quality traits, yet few fruit-specific promoters have been identified, for citrus fruit development
Additional tomato fruit-specific promoters include the promoter of the polygalacturonase gene (PG), which plays a role in cell wall degradation during fruit ripening [20,21,22,23]; the promoter of the T-proline-rich protein F1 (TPRP-F1) gene, which is expressed in the ovary and young fruit [24]; and the promoter of ACC synthase [25, 26]
Taken together our results demonstrate that CitWAXp, CitJuSacp, CitVO1p, CitUNKp and PamMybAp are strong fruit-preferential promoters and CitSEPp is a tightly controlled fruit/seed-specific promoter for fruit biotechnology based on observed GUSPlus expression patterns and the intensity of staining observed in both transient and stable transgenic tomato tissues
Summary
Promoters that confer expression in fruit tissues are important tools for genetic engineering of fruit quality traits, yet few fruit-specific promoters have been identified, for citrus fruit development. Dasgupta et al BMC Biotechnology (2020) 20:43 and protein and rich in dietary fiber, vitamin C, B vitamins, (thiamin, pyridoxine, niacin, riboflavin, pantothenic acid, and folate), vitamin A (β-cryptoxanthin) carotenoids, flavonoids, and limonoids [9,10,11]. These biological active compounds are important to human health for their antioxidant quality and protection from various chronic diseases [8]. In many fruit species such as citrus and plum, the availability of fruit-specific promoters suitable for use in genetic engineering is still limited
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