The RUBY reporter enables efficient haploid identification in maize and tomato

背景回顾：In vivo haploid induction has been extended from maize to monocotyledonous plants like rice, wheat, millet and dicotyledonous plants such as tomato, rapeseed, tobacco and cabbage. Accurate identification of haploids is a crucial step of doubled haploid technology, where a useful identification marker is very pivotal. R1-njis an extensively used visual marker for haploid identification in maize. RFP and eGFP have been shown to be feasible in identifying haploid. 

提出问题：However, these methods are either limited to specific species, or require specific equipment. It still lacks an efficient visual marker that is practical across different crop species. 

主要发现：In this study, we introduced the RUBYreporter, a betalain biosynthesis system, into maize and tomato haploid inducers as a new marker for haploid identification. 

结果1-玉米：Results showed that expression of RUBY could result in deep betalain pigmentation in maize embryos as early as 10 days after pollination, and enabled 100% accuracy of immature haploid embryo identification. 

结果2-番茄：Further investigation in tomato revealed that the new marker led to deep red pigmentation in radicles and haploids can be identified easily and accurately. 

结论：The results demonstrated that the RUBYreporter is a background-independent and efficient marker for haploid identification and would be promising in doubled haploid breeding across different crop species.

体内单倍体诱导已经从玉米中拓展到了水稻、小麦、谷子等单子叶植物以及番茄、油菜、烟草和卷心菜等双子叶植物中。精确鉴定单倍体是双单倍体技术的重要环节，其中一个有效的鉴定标记是重中之重。在玉米中，R1-nj 被广泛用于单倍体鉴定的可视化标记。RFP和eGFP已经被证明在鉴定单倍体时是可行的。但是，这些方法要么限制于特定的物种，要么需要特定的仪器。目前，仍缺乏一个在农业生产实践中适用的高效单倍体鉴定标记。本文中，作者将一个甜菜素生物合成RUBY报告系统引入到了玉米和番茄的单倍体诱导体中，作为鉴定单倍体的标记。结果显示，RUBY的表达会导致在授粉10天后玉米胚胎中甜菜素色素的沉积，并且能够100%的鉴定未成熟的单倍体胚胎。进一步在番茄中的研究显示，这一新的标记会导致胚根着深红色，从而能够既简便又精确鉴定单倍体。本文的研究结果表明RUBY报告系统是一个独立于物种生物学背景的高效单倍体鉴定标记，有潜力作为单倍体鉴定标记用于多个作物的双单倍体育种。

** 陈绍江 **