Members of the tomato FRUITFULL MADS-box family regulate style abscission and fruit ripening.

Shufen Wang,Zhidan Luo,Gang Lu,Hanxia Li,Taotao Wang,Zheng Hou,Zhibiao Ye,Junhong Zhang

doi:10.1093/jxb/eru137

Shufen Wang, Zhidan Luo + Show 6 more

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https://doi.org/10.1093/jxb/eru137

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Abstract

The tomato (Solanum lycopersicum) protein MADS-RIN plays important roles in fruit ripening. In this study, the functions of two homologous tomato proteins, FUL1 and FUL2, which contain conserved MIKC domains that typify plant MADS-box proteins, and which interact with MADS-RIN, were analysed. Transgenic functional analysis showed that FUL1 and FUL2 function redundantly in fruit ripening regulation, but exhibit distinct roles in the regulation of cellular differentiation and expansion. Over-expression of FUL2 in tomato resulted in a pointed tip at the blossom end of the fruit, together with a thinner pericarp, reduced stem diameter, and smaller leaves, but no obvious phenotypes resulted from FUL1 over-expression. Dual suppression of FUL1 and FUL2 substantially inhibited fruit ripening by blocking ethylene biosynthesis and decreasing carotenoid accumulation. In addition, the levels of transcript corresponding to ACC SYNTHASE2 (ACS2), which plays a key role in ethylene biosynthesis, were significantly decreased in the FUL1/FUL2 knock-down tomato fruits. Overall, our results suggest that FUL proteins can regulate tomato fruit ripening through fine-tuning ethylene biosynthesis and the expression of ripening-related genes.

Highlights

Members of MADS-box transcription factor families, which are widely distributed among animal and plant taxa, contain a conserved domain of approximately 60 amino acids in the N-terminal region, named the MADS-box (M) domain
VmTDR4, a FRUITFULL homologue from bilberry (Vaccinium myrtillus) was found to regulate anthocyanin biosynthesis during fruit ripening (Jaakola et al, 2010). These results suggest that FUL1 and FUL2 might play important roles during tomato fruit development, a hypothesis that was tested in this current study through the functional analysis of transgenic plants
FUL1 was first identified in tomato as a floral identity gene (Pnueli et al, 1991), but the expression pattern of FUL1 suggests a possible role in fruit development and ripening (Busi et al, 2003; Eriksson et al, 2004)

Summary

Introduction

Members of MADS-box transcription factor families, which are widely distributed among animal and plant taxa, contain a conserved domain of approximately 60 amino acids in the N-terminal region, named the MADS-box (M) domain. Plant MADS-box genes were first investigated in the context of functional studies of Arabidopsis floral organ development and flowering time (Sommer et al, 1990; Yanofsky et al, 1990) and are the major modules in the well-known ABCDE model of floral organs.

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