CsAP3: A Cucumber Homolog to Arabidopsis APETALA3 with Novel Characteristics

Abstract

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 CsETR1 in stage 6 female flowers of cucumber (Cucumis sativus 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 CsETR1 is down regulated in the stamen, we characterized a cucumber MADS box gene homologous to Arabidopsis AP3, CsAP3. We demonstrated that CsAP3 is functionally equivalent to the Arabidopsis B-class MADS gene AP3. However, three novel characteristics of CsAP3 were found. These include firstly, binding and activating CsETR1 promoter in vitro and in vivo; 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 CsETR1. These findings revealed not only the conserved function of CsAP3 as a B-class floral identity gene, but also its unique functions in regulation of female flower development in cucumber.

Genetic and molecular bases of cucumber (Cucumis sativus L.) sex determination

“…The expression of CsETR1 is stamenspecific downregulated in female floral buds. CsAP3, a B-class MADS-box gene with an equivalent function in organ identity determination, is required for the stamenspecific regulation of CsETR1 expression in female flower development, as it can bind and activate the CsETR1 promoter (Sun et al 2016). CsAP3 expression is decreased in flowers at higher nodes, which is consistent with the expression pattern of CsETR1.…”

Isolation and characterization of a MADS-box gene in cucumber (Cucumis sativus L.) that affects flowering time and leaf morphology in transgenic Arabidopsis

“…Cucumber (Cucumis sativus L.) is a major vegetable crop cultivated worldwide, and is also a model system for flower development studies owing to its diversity of floral sex types [38][39][40]. Our previous study had identified 43 MADS-box family genes in cucumber, and some of them may function in determining the flower organ identity and floral transition [1].…”

The MADS-Box Gene CsSHP Participates in Fruit Maturation and Floral Organ Development in Cucumber

“…Previous study revealed the expression pattern of 43 MADS-box genes in cucumber (Hu and Liu, 2012). CUM1, CUM10, CUM26, CsAP3, and CsSEP2 are currently known cucumber MADS-box genes that play essential roles in flower and fruit development (Kater et al, 1998;Kater et al, 2001;Sun et al, 2016;Wang et al, 2016), whereas there are still a considerable portion of MADS-box genes need to be functionally characterized. In this study, we identified the CsSHP gene in cucumber and revealed the roles in fruit maturation and floral organ determination.…”