Abstract：
The sex of dioecious plants is mainly determined by genetic factors, but it can also be converted by environmental cues such as exogenous phytohormones. Gibberellic acids (GAs) are well-known inducers of flowering and sexual development, yet the pathway of gibberellin-induced sex conversion in dioecious spinach (Spinacia oleracea L.) remains elusive. Based on sex detection before and after GA3 application using T11A and SSR19 molecular markers, we confirmed and elevated the masculinization effect of GA on a single female plant through exogenous applications of GA3, showing complete conversion and functional stamens. Silencing of GIBBERELLIC ACID INSENSITIVE (SpGAI), a single DELLA family protein that is a central GA signaling repressor, results in similar masculinization. We also show that SpGAI can physically interact with the spinach KNOX transcription factor SHOOT MERISTEMLESS (SpSTM), which is a homolog of the flower meristem identity regulator STM in Arabidopsis. The silencing of SpSTM also masculinized female flowers in spinach. Furthermore, SpSTM could directly bind the intron of SpPI to repress SpPI expression in developing female flowers. Overall, our results suggest that GA induces a female masculinization process through the SpGAI-SpSTM-SpPI regulatory module in spinach. These insights may help to clarify the molecular mechanism underlying the sex conversion system in dioecious plants while also elucidating the physiological basis for the generation of unisexual flowers so as to establish dioecy in plants.
摘要：
雌雄异株植物的性别主要由遗传因素决定，但它也可以通过环境线索如外源植物激素转化。赤霉素（GA）是众所周知的开花和性发育的诱导剂，然而，赤霉素在雌雄异株菠菜（SpinaciaoleraceaL.）中诱导的性别转换的途径仍然难以捉摸。基于使用T11A和SSR19分子标记的GA3应用前后的性别检测，我们通过外源施用GA3证实并提高了GA对单个雌性植物的男性化效应，显示完全转化和功能性雄蕊。对赤霉素不敏感（SpGAI）的沉默，一个单一的DELLA家族蛋白，是一个中央GA信号抑制因子，结果类似的男性化。我们还表明，SpGAI可以与菠菜KNOX转录因子SHOTMERISTEMLESS（SpSTM）物理相互作用，这是拟南芥中花分生组织身份调节剂STM的同源物。SpSTM的沉默也使菠菜中的雌花男性化。此外，SpSTM可以直接结合SpPI的内含子，从而抑制发育中雌花中的SpPI表达。总的来说,我们的结果表明，GA通过菠菜中的SpGAI-SpSTM-SpPI调节模块诱导女性男性化过程。这些见解可能有助于阐明雌雄异株植物性别转换系统的分子机制，同时也阐明了单性花产生的生理基础，从而在植物中建立了雄花。
