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Mol Plant. 2016 Sep 6;9(9):1315-1327. doi: 10.1016/j.molp.2016.06.018. Epub 2016 Jul 9.

An ACC Oxidase Gene Essential for Cucumber Carpel Development.

Author information

1
Hunan Vegetable Research Institute, Hunan Academy of Agricultural Sciences, Changsha 410125, China.
2
Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agriculture, Sino-Dutch Joint Laboratory of Horticultural Genomics, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
3
Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agriculture, Sino-Dutch Joint Laboratory of Horticultural Genomics, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China; Agricultural Genomic Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen 518120, China.
4
Institute of Agricultural Product Processing, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
5
College of Life Sciences, Peking University, Beijing 100871, China.
6
Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agriculture, Sino-Dutch Joint Laboratory of Horticultural Genomics, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China; Agricultural Genomic Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen 518120, China. Electronic address: huangsanwen@caas.cn.

Abstract

Sex determination in plants gives rise to unisexual flowers that facilitate outcrossing and enhance genetic diversity. In cucumber and melon, ethylene promotes carpel development and arrests stamen development. Five sex-determination genes have been identified, including four encoding 1-aminocyclopropane-1-carboxylate (ACC) synthase that catalyzes the rate-limiting step in ethylene biosynthesis, and a transcription factor gene CmWIP1 that corresponds to the Mendelian locus gynoecious in melon and is a negative regulator of femaleness. ACC oxidase (ACO) converts ACC into ethylene; however, it remains elusive which ACO gene in the cucumber genome is critical for sex determination and how CmWIP1 represses development of female flowers. In this study, we discovered that mutation in an ACO gene, CsACO2, confers androecy in cucumber that bears only male flowers. The mutation disrupts the enzymatic activity of CsACO2, resulting in 50% less ethylene emission from shoot tips. CsACO2 was expressed in the carpel primordia and its expression overlapped with that of CsACS11 in female flowers at key stages for sex determination, presumably providing sufficient ethylene required for proper CsACS2 expression. CmACO3, the ortholog of CsACO2, showed a similar expression pattern in the carpel region, suggesting a conserved function of CsACO2/CmACO3. We demonstrated that CsWIP1, the ortholog of CmWIP1, could directly bind the promoter of CsACO2 and repress its expression. Taken together, we propose a presumably conserved regulatory module consisting of WIP1 transcription factor and ACO controls unisexual flower development in cucumber and melon.

KEYWORDS:

ACC oxidase; carpel development; cucumber; sex determination

PMID:
27403533
DOI:
10.1016/j.molp.2016.06.018
[Indexed for MEDLINE]
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