AUTHOR=Sun Jin-Jing , Li Feng , Wang Dong-Hui , Liu Xiao-Feng , Li Xia , Liu Na , Gu Hai-Tao , Zou Cheng , Luo Jing-Chu , He Chao-Xing , Huang San-Wen , Zhang Xiao-Lan , Xu Zhi-Hong , Bai Shu-Nong 

TITLE=CsAP3: A Cucumber Homolog to Arabidopsis APETALA3 with Novel Characteristics

JOURNAL=Frontiers in Plant Science

VOLUME=Volume 7 - 2016

YEAR=2016

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2016.01181

DOI=10.3389/fpls.2016.01181

ISSN=1664-462X

ABSTRACT=<p>In our previous efforts to understand the regulatory mechanisms of cucumber unisexual flower development, we observed a stamen-specific down-regulation of the ethylene receptor <italic>CsETR1</italic> in stage 6 female flowers of cucumber (<italic>Cucumis sativus</italic> L.). This down-regulation is correlated with the primordial anther-specific DNA damage that characterizes inappropriate stamen development in cucumber female flowers. To understand how <italic>CsETR1</italic> is down regulated in the stamen, we characterized a cucumber MADS box gene homologous to <italic>Arabidopsis AP3</italic>, <italic>CsAP3</italic>. We demonstrated that <italic>CsAP3</italic> is functionally equivalent to the <italic>Arabidopsis</italic> B-class MADS gene <italic>AP3</italic>. However, three novel characteristics of CsAP3 were found. These include firstly, binding and activating <italic>CsETR1</italic> promoter <italic>in vitro</italic> and <italic>in vivo</italic>; secondly, containing a GV repeat in its C-terminus, which is conserved in cucurbits and required for the transcription activation; and thirdly, decreased expression as the node number increases, which is similar to that found for <italic>CsETR1</italic>. These findings revealed not only the conserved function of <italic>CsAP3</italic> as a B-class floral identity gene, but also its unique functions in regulation of female flower development in cucumber.</p>