Default Sex and Single Gene Sex Determination in Dioecious Plants Article Swipe
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· 2020
· Open Access
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· DOI: https://doi.org/10.3389/fpls.2020.01162
· OA: W3045783552
A well-established hypothesis for the evolution of dioecy involves two genes linked at a sex-determining region (SDR). Recently there has been increased interest in possible single gene sex determination. Work in <i>Populus</i> has finally provided direct experimental evidence for single gene sex determination in plants using CRISPR-Cas9 to knock out a single gene and convert individuals from female to male. In poplar, the feminizing factor <i>popARR17</i> acts as a "master regulator", analogous to the mammalian masculinizing factor SRY. The production of fully functional males from females by a simple single gene knockout is experimental evidence that an antagonistic male-determining factor does not exist in <i>Populus</i>. Mammals have a "default sex" (female), as do poplar trees (<i>Populus</i>), although the default sex in poplars is male. The occurrence of single gene sex determination with a default sex may be much commoner in plants than hitherto expected, especially when dioecy evolved <i>via</i> monoecy. The master regulator does not even need to be at the SDR (although it may be). In most poplars the feminizing factor <i>popARR17</i> is not at the SDR, but instead a negative regulator of it. So far there is little information on how high-level regulators are connected to floral phenotype. A model is presented of how sex-determining genes could lead to different floral morphologies <i>via</i> MADS-box floral developmental genes.
