Cucumber CsTRY Negatively Regulates Anthocyanin Biosynthesis and Trichome Formation When Expressed in Tobacco.

Leyu Zhang,Jian Pan,Huanle He,Run Cai,Gang Wang,Hui Du,Junsong Pan

doi:10.3389/fpls.2019.01232

Abstract

The development of trichomes (spines) on cucumber fruits is an important agronomic trait. It has been reported that two MYB family members, CsMYB6 (Csa3G824850) and CsTRY (Csa5G139610) act as negative regulators of trichome or fruit spine initiation. To further study the functions of these two genes, we overexpressed them in tobacco, and found that the flowers and seed coats of transformants overexpressing CsTRY displayed an unexpected defect in pigmentation that was not observed in plants overexpressing CsMYB6. Moreover, the expression of key genes in the flavonoid synthesis pathway was repressed in CsTRY overexpressing plants, which resulted in the decrease of several important flavonoid secondary metabolites. In addition, CsTRY could interact with the AN1 homologous gene CsAN1 (Csa7G044190) in cucumber, which further confirmed that CsTRY not only regulates the development of fruit spines, but also functions in the synthesis of flavonoids, acting as the repressor of anthocyanin synthesis.

Highlights

Cucumber (Cucumis sativus L.) is a horticultural crop that is consumed worldwide (Huang et al, 2009; Yundaeng et al, 2015), and trichomes on the fruit are considered as an important commodity trait (Zhang et al, 2010; Yang et al, 2014; Li et al, 2015; Pan et al, 2015)
Anthocyanin quantification results measured by spectrophotometer revealed that anthocyanin accumulation in the petals of 35S:CsTRY transgenic tobacco plants was clearly reduced, indicating that CsTRY may be negatively regulating the synthesis of tobacco anthocyanin (Figure 1D)
The genes regulating unicellular trichome developments are usually related to anthocyanin synthesis (Jin and Martin, 1999)

Summary

Introduction

Cucumber (Cucumis sativus L.) is a horticultural crop that is consumed worldwide (Huang et al, 2009; Yundaeng et al, 2015), and trichomes (spines) on the fruit are considered as an important commodity trait (Zhang et al, 2010; Yang et al, 2014; Li et al, 2015; Pan et al, 2015). The cucumber fruit, a pepo that develops from the ovary and receptacle, is covered with a thick cuticle, tubercules and trichomes (spines) (Roth, 1977; Wang et al, 2015). In the model plant Arabidopsis thaliana, trichome developments is initiated by a ternary complex (GL1-GL3/EGL1-TTG1) from epidermal cells, which leads to the expression of GL2 and TRY (Oppenheimer et al, 1991; Galway et al, 1994; Walker, 1999; Payne et al, 2000; Szymanski et al, 2000; Larkin et al, 2003; Zhang et al, 2003). In Artemisia annua, an MYB family member, AaMIXTA1, can promotes trichome development and regulates cuticle biosynthesis. These reports suggest that, the genes that regulate trichome developments usually function in secondary metabolite biosynthesis (Yan et al, 2018)

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Conclusion