A CsTu-TS1 regulatory module promotes fruit tubercule formation in cucumber.

Dehua Ma,Jinan Pang,Huazhong Ren,Chen Jian,Shuo Xu,Sen Yang,Yanling Cai,Wenzhu Qi,Mingming Dong,Xingwang Liu,Bin Liu,Shudan Xue,Ezra S. Bartholomew,Changlong Wen,Ting Wang

doi:10.1111/pbi.12977

Abstract

SummaryThe fruit epidermal features such as the size of tubercules are important fruit quality traits for cucumber production. But the mechanisms underlying tubercule formation remain elusive. Here, tubercule size locus CsTS1 was identified by map‐based cloning and was found to encode an oleosin protein. Allelic variation was identified in the promoter region of CsTS1, resulting in low expression of CsTS1 in all 22 different small‐warty or nonwarty cucumber lines. High CsTS1 expression levels were closely correlated with increased fruit tubercule size among 44 different cucumber lines. Transgenic complementation and RNAi‐mediated gene silencing of CsTS1 in transgenic cucumber plants demonstrated that CsTS1 positively regulates the development of tubercules. CsTS1 is highly expressed in the peel at fruit tubercule forming and enlargement stage. Auxin content and expression of three auxin signalling pathway genes were altered in the 35S:CsTS1 and CsTS1‐RNAi fruit tubercules, a result that was supported by comparing the cell size of the control and transgenic fruit tubercules. CsTu, a C2H2 zinc finger domain transcription factor that regulates tubercule initiation, binds directly to the CsTS1 promoter and promotes its expression. Taken together, our results reveal a novel mechanism in which the CsTu‐TS1 complex promotes fruit tubercule formation in cucumber.

Highlights

Cucumber (Cucumis sativus; 2n = 2x = 14) is an economically important vegetable crop cultivated around the world (Huang et al, 2009; Li et al, 2013; Yang et al, 2014)
Our research indicates that CsTS1 positively regulates the development of tubercules and directly interact with CsTu, a C2H2 zinc finger domain transcription factor that regulates tubercule initiation
CsTS1 controls the size of cucumber fruit tubercules

Summary

Introduction

In cucumber fruits, when tubercules are combined with spines, the result is a characteristic warty (Wty) trait, and on this basis, cucumber lines are divided into those with Wty and non-Wty (nWty) fruits (Yang et al, 2014). The Wty trait is important for assessing cucumber appearance and commodity quality and it directly affects the market value (Yang et al, 2014). During the development of large-warty (L-Wty) cucumber fruit, tubercules and trichomes are randomly scattered on the fruit surface relative to the deep ridges along the length of the fruit (Ando et al, 2012; Chen et al, 2014). There is considerable interest in gaining a greater understanding of the molecular mechanisms underlying cucumber fruit tubercule development to enhance the economic value of cucumber production and breeding programmes

Results

Discussion

Conclusion