FvCO4在生长素诱导草莓果实早期发育中的作用及机制研究

Formation and development of fruits are the basis of the production for horticultural crops with fruits as products. Development of the early-stage fruit of strawberry is distinctly induced by auxin. The core tissues for the development and expansion of strawberry fruit are pith and cortex. Our previous research found that FvCO4, a homologue of CONSTANS in strawberry, expressed specifically in the pith and cortex of the early-stage strawberry fruit. While treated with emasculation or auxin, respectively, expression of FvCO4 was also correspondingly regulated following the changed early-fruit development. Preliminary result of knockout of this gene by CRISPR showed that the early-stage fruit development was also disturbed. To illuminate its possible function in the early-stage development of strawberry fruit induced by auxin, in this project, the function of FvCO4 in the fruit development will be further conformed by its overexpression in strawberry. At the meantime, histological sections of the fruits in two kinds of transformants will be checked to reveal the histological and cellular basis of its function. To illuminate the possible role of FvCO4 in the auxin signal transmission, transformants of knocked-out or overexpression will be treated with auxin or castration separately and then the fruit development phenotypes will be checked. After the confirmation of the transcriptional regulation role of FvCO4 on FvCOT2, function of FvFT2 in the fruit development will be further confirmed by its overexpression and so as to evaluate the possible role of CO-FT module in the regulation of fruit development. Finally, the transcriptional levels of the genes related to cell division in the early-stage fruit of the transformants will be checked. And the differentially expressed genes among them will be further checked to illuminate the transcritional regulation on them of FvFT2 or FvCO4. At the same time, other factors that may be involved in this pathway will also be identified by RNA-Seq. This research aimed to identify the function of FvCO4 in the early-stage fruit development of strawberry induced by auxin.

果实形成和发育是瓜果类园艺作物生产的基础。草莓果实早期发育受生长素诱导，髓部和皮层是其发育的核心部位，前期研究发现草莓CONSTANS类基因FvCO4在髓部和皮层中特异高表达，并显著响应影响果实发育的生长素阻断或喷施处理，CRISPR敲除表明其功能缺失导致果实发育明显受阻。本项目拟在进一步获得过表达植株基础上，明确FvCO4在草莓果实发育中的功能并鉴定其组织细胞学基础。对敲除和过表达株系分别处以生长素和去雄处理，确认生长素在果实发育中的作用是否通过FvCO4介导。鉴定FvCO4对候选靶基因FvFT2的转录调控，进而过表达FvFT2明确FvCO4是否通过CO-FT元件发挥作用。检测转化株早期果实中细胞分裂相关基因表达变化，鉴定FvFT2或FvCO4对差异表达基因的转录调控，通过RNA-Seq比较筛选其它关联因子，并加以鉴定。本项目旨在揭示FvCO4在生长素诱导草莓果实早期发育中的作用及机制。

果实是瓜果类园艺作物的商品器官，在发现草莓CONSTANS类基因FvCO4可能参与草莓果实发育调控的基础上，本项目通过一系列研究揭示了其介导生长素信号调控草莓生长发育的作用机制。项目研究证实了FvCO4基因的功能与草莓果实发育有关，该基因的CRISPR敲除导致草莓果实败育，而瞬时超表达则可使去雄草莓果实进一步发育；FvCO4基因的功能与果实中生长素信号传导有关，生长素信号通过生长素响应因子ARF调控FvCO4的表达；FvCO4的表达水平变化则会通过影响FvCDKB、FvKNOLLE等细胞分裂有关基因的表达来影响果实细胞分裂；此外FvCO4蛋白则可以结合到FvFT2基因启动子上调控其表达，而后者的超表达同样可以引起去雄草莓果实的发育。本项目研究结果揭示了CO-FT通路在草莓果实发育调控中的新功能，可以为草莓生产中果实败育、畸形等问题的解决提供理论参考。