Abstract
α-Farnesene, a sesquiterpene volatile compound plays an important role in plant defense and is known to be associated with insect attraction and with superficial scald of apple and pear fruits during cold storage. But the mechanism whereby transcription factors regulate apple α-farnesene biosynthesis has not been clarified. Here, we report that two transcription factors, MdMYC2 and MdERF3 regulated α-farnesene biosynthesis in apple fruit. Dual-luciferase assays and Y1H assays indicated that MdMYC2 and MdERF3 effectively trans-activated the MdAFS promoter. EMSAs showed that MdERF3 directly binds the DRE motif in the MdAFS promoter. Subsequently, overexpression of MdMYC2 and MdERF3 in apple calli markedly activated the transcript levels of MdHMGR2 and MdAFS. Furthermore, transient overexpression of MdMYC2 and MdERF3 in apple fruit significantly increased MdAFS expression and hence, α-farnesene production. These results indicate that MdMYC2 and MdERF3 are positive regulators of α-farnesene biosynthesis and have important value in genetic engineering of α-farnesene production.
Highlights
Plants produce a large number of metabolites that are essential for ecological interactions and terpenes are natural products of the largest and structurally most diverse class (Reddy et al, 2017)
By screening transcription factors involved in secondary metabolic regulation, we studied whether these transcription factors are participated in regulating the expression of a-farnesene synthase, thereby affecting the biosynthesis of a-farnesene
Our results revealed that transcription factors MdMYC2 and MdERF3 effectively activated the promoter region of MdAFS, which is the terminal enzyme gene in the a-farnesene biosynthesis pathway; they activated the expression of the MdAFS gene, and promoted the accumulation the a-farnesene
Summary
Plants produce a large number of metabolites that are essential for ecological interactions and terpenes are natural products of the largest and structurally most diverse class (Reddy et al, 2017). Terpenes play an important role in the communication between plants and the environment, between plants and animals, and between plants and plants; they can attract pollinators and seed spreaders, and they can act as defense agents against herbivores and pathogens. They protect plants from abiotic stress phenomena, such as high light intensity, high temperature, and oxidative stress, among others. The oxidative product of a-farnesene, are widely considered as a principal cause of scald, the physiological disorder of apple and pear, which intensify when fruits are transferred to ambient temperature for transportation to the market (Huelin and Coggiola, 1970; Ingle and D’Souza, 1989; Rowan et al, 1995). Overexpression of a-farnesene synthase in pathogen-sensitive soybeans enhances plant antimicrobial activity and a-farnesene has been considered as a potential biofuel precursor (Lin et al, 2017)
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