A tomato MADS-box protein, SlCMB1, regulates ethylene biosynthesis and carotenoid accumulation during fruit ripening

Jianling Zhang,Zongli Hu,Vanluc Nguyen,Xuhu Guo,Fenfen Li,Qiyuan Yao,Guoping Chen

doi:10.1038/s41598-018-21672-8

Jianling Zhang, Zongli Hu + Show 5 more

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https://doi.org/10.1038/s41598-018-21672-8

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Journal: Scientific Reports	Publication Date: Feb 21, 2018
Citations: 53	License type: open-access

Affiliation: Chongqing University

Abstract

The MADS-box transcription factors play essential roles in many physiological and biochemical processes of plants, especially in fruit ripening. Here, a tomato MADS-box gene, SlCMB1, was isolated. SlCMB1 expression declined with the fruit ripening from immature green to B + 7 (7 days after Breaker) fruits in the wild type (WT) and was lower in Nr and rin mutants fruits. Tomato plants with reduced SlCMB1 mRNA displayed delayed fruit ripening, reduced ethylene production and carotenoid accumulation. The ethylene production in SlCMB1-RNAi fruits decreased by approximately 50% as compared to WT. The transcripts of ethylene biosynthesis genes (ACS2, ACS4, ACO1 and ACO3), ethylene-responsive genes (E4, E8 and ERF1) and fruit ripening-related genes (RIN, TAGL1, FUL1, FUL2, LoxC and PE) were inhibited in SlCMB1-RNAi fruits. The carotenoid accumulation was decreased and two carotenoid synthesis-related genes (PSY1 and PDS) were down-regulated while three lycopene cyclase genes (CYCB, LCYB and LCYE) were up-regulated in transgenic fruits. Furthermore, yeast two-hybrid assay showed that SlCMB1 could interact with SlMADS-RIN, SlMADS1, SlAP2a and TAGL1, respectively. Collectively, these results indicate that SlCMB1 is a new component to the current model of regulatory network that regulates ethylene biosynthesis and carotenoid accumulation during fruit ripening.

Highlights

Fruit ripening has always been the focus of scientific research, which is mainly due to the uniqueness of this biological process and the important role that fruits provide nutrition for animal and human[1,2]
RNAi repression of SlCMB1 was carried out to study the exact role of SlCMB1 in fruit ripening of tomato, and our results showed that suppression of SlCMB1 results in inhibited ethylene biosynthesis and reduced carotenoid accumulation during tomato fruit ripening
Phylogenetic analysis displayed that SlCMB1 belongs to the SEPALLATA (SEP) clade and showed higher similarity with SlMADS-RIN compared with other functional MADS-box proteins (Fig. 1B)

Summary

Introduction

Fruit ripening has always been the focus of scientific research, which is mainly due to the uniqueness of this biological process and the important role that fruits provide nutrition for animal and human[1,2]. Tomato is generally used as an excellent model plant for fruit ripening study, because of several desirable attributes, such as short life cycle, small genome size, efficient stable transformation, high-density genetic maps and the completion of tomato genome sequence[28,29,30], and the existence of lots of well-characterized ripening tomato mutants, such as Green ripe (Gr), never ripe (Nr), color nonripening (cnr) and ripening inhibitor (rin), have been found and studied[31,32,33,34,35] These superiority and mutants of tomato help us to reveal the mechanism of fruit ripening[36]. Loss one of these MADS-box gene, the SlMADS-RIN, results in failure of fruit ripening, whereas loss of the other, SlMADS-MC, the phenotypes of enlarged sepals and altered inflorescence architecture are observed[32]

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