Ectopic Expression of VvSUC27 Induces Stenospermocarpy and Sugar Accumulation in Tomato Fruits.

Yumeng Cai,Lei Zhu,Nan Zhang,Wenjie Dong,Zhefang Deng,Yali Zhang,Wenrui Tu,Ling Yin,Han Gao,Jing Yan,Jinxu Xu,Jie Wang,Qingyong Meng

doi:10.3389/fpls.2021.759047

Abstract

Seedless fruits are favorable in the market because of their ease of manipulation. Sucrose transporters (SUTs or SUCs) are essential for carbohydrate metabolism in plants. Whether SUTs participate directly in causing stenospermocarpy, thereby increasing fruit quality, remains unclear. Three SUTs, namely, VvSUC11, VvSUC12, and VvSUC27 from Vitis vinifera, were characterized and ectopic expression in tomatoes. VvSUC11- and VvSUC12-overexpressing lines had similar flower and fruit phenotypes compared with those of the wild type. VvSUC27-overexpressing lines produced longer petals and pistils, an abnormal stigma, much less and shrunken pollen, and firmer seedless fruits. Moreover, produced fruits from all VvSUC-overexpressing lines had a higher soluble solid content and sugar concentration. Transcriptomic analysis revealed more genes associated with carbohydrate metabolism and sugar transport and showed downregulation of auxin- and ethylene-related signaling pathways during early fruit development in VvSUC27-overexpressing lines relative to that of the wild type. Our findings demonstrated that stenospermocarpy can be induced by overexpression of VvSUC27 through a consequential reduction in nutrient delivery to pollen at anthesis, with a subsequent downregulation of the genes involved in carbohydrate metabolism and hormone signaling. These commercially desirable results provide a new strategy for bioengineering stenospermocarpy in tomatoes and in other fruit plants.

Highlights

Carbon fixation occurs in photosynthetic source organs, and the products are exported as sucrose to non-photosynthetically heterotrophic sink organs (Koch, 2004)
VvSUC11, VvSUC12, and VvSUC27 from Vitis vinifera were chosen for investigation using Solanum lycopersicum “Micro-Tom” because they have different gene expression patterns and properties (Manning et al, 2001; Zhang et al, 2008; AfoufaBastien et al, 2010; Cai et al, 2019) and all have a close correlation with sugar accumulation in the fruit
T0 further characterize the biological function of VvSUC11, VvSUC12, and VvSUC27 in fruit berries, the overexpression vectors 35S:: VvSUC11, VvSUC12, and VvSUC27 were constructed and transformed into Solanum lycopersicum cv

Summary

Introduction

Carbon fixation occurs in photosynthetic source organs, and the products are exported as sucrose to non-photosynthetically heterotrophic sink organs (Koch, 2004). The use of SUTs in the translocation of sucrose is required for plant development. The antisense inhibition of both SlSUT1 and SlSUT2 prevents the production of normal tomato fruits. The phloem loading and supply to terminal sink organs of SlSUT1 antisense plants is disturbed and delays the development of storage sink organs, whereas SlSUT2 antisense inhibition could affect tomato fruit (Hackel et al, 2006). CitSUT1 is strongly expressed in the source and sugar-exporting organs. CitSUT2 is expressed more strongly in the sink and sugarimporting organs (Yao Li et al, 2003). Cucumber (Cucumis sativus) CsSUT1-RNA interference (RNAi) lines exhibited a decreased content of sucrose, hexose, and starch with male sterility (Sun et al, 2019), whereas suppressing CsSUT2 decreased the sucrose level and increased the stachyose content in leaves (Ma et al, 2019b)

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Conclusion