<b>The control of carpel determinacy pathway leads to sex determination</b> <b>in cucurbits</b>

Abstract

Male and female unisexual flowers evolved from hermaphroditic ancestors, and control of flower sex is useful for plant breeding. We isolated a female-to-male sex transition mutant in melon and identified the causal gene as the carpel identity gene &lt;i&gt;CRABS CLAW (CRC)&lt;/i&gt;. We show that the master regulator of sex determination in cucurbits, the transcription factor &lt;i&gt;WIP1&lt;/i&gt; whose expression orchestrates male flower development, recruits the corepressor TOPLESS to the &lt;i&gt;CRC&lt;/i&gt; promoter to suppress its expression through histone deacetylation. Impairing TOPLESS-WIP1 physical interaction leads to &lt;i&gt;CRC&lt;/i&gt; expression, carpel determination, and consequently the expression of the stamina inhibitor, the aminocyclopropane-1-carboxylic acid synthase 7 (&lt;i&gt;CmACS7&lt;/i&gt;), leading to female flower development. Our findings suggest that sex genes evolved to interfere with flower meristematic function, leading to unisexual flower development.