AUTHOR=Zhang Yan , Zhao Guiye , Li Yushun , Mo Ning , Zhang Jie , Liang Yan 

TITLE=Transcriptomic Analysis Implies That GA Regulates Sex Expression via Ethylene-Dependent and Ethylene-Independent Pathways in Cucumber (Cucumis sativus L.)

JOURNAL=Frontiers in Plant Science

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2017.00010

DOI=10.3389/fpls.2017.00010

ISSN=1664-462X

ABSTRACT=<p>Sex differentiation of flower buds is an important developmental process that directly affects fruit yield of cucumber (<italic>Cucumis sativus</italic> L.). Plant hormones, such as gibberellins (GAs) and ethylene can promote development of male and female flowers, respectively, however, the regulatory mechanisms of GA-induced male flower formation and potential involvement of ethylene in this process still remain unknown. In this study, to unravel the genes and gene networks involved in GA-regulated cucumber sexual development, we performed high throughout RNA-Seq analyses that compared the transcriptomes of shoot tips between GA<sub>3</sub> treated and untreated gynoecious cucumber plants. Results showed that GA<sub>3</sub> application markedly induced male flowers but decreased ethylene production in shoot tips. Furthermore, the transcript levels of <italic>M</italic> (<italic>CsACS2</italic>) gene, ethylene receptor <italic>CsETR1</italic> and some ethylene-responsive transcription factors were dramatically changed after GA<sub>3</sub> treatment, suggesting a potential involvement of ethylene in GA-regulated sex expression of cucumber. Interestingly, GA<sub>3</sub> down-regulated transcript of a C-class floral homeotic gene, <italic>CAG2</italic>, indicating that GA may also influence cucumber sex determination through an ethylene-independent process. These results suggest a novel model for hormone-mediated sex differentiation and provide a theoretical basis for further dissection of the regulatory mechanism of male flower formation in cucumber.</p><p><bold>Statement:</bold> We reveal that GA can regulate sex expression of cucumber via an ethylene-dependent manner, and the <italic>M</italic> (<italic>CsACS2</italic>), <italic>CsETR1</italic>, and <italic>ERFs</italic> are probably involved in this process. Moreover, <italic>CAG2</italic>, a C-class floral homeotic gene, may also participate in GA-modulated cucumber sex determination, but this pathway is ethylene-independent.</p>