In Vitro Organogenesis

植物细胞和组织在适当条件下去分化并产生芽和根的能力构成了现代植物生物技术的基础。产生新的功能芽和根的关键事件是顶端分生组织的形成。顶端分生组织负责植物初生体（植物中所有细胞的母体）的组织和器官形成。尽管近年来在了解正常植物发育过程中顶端分生组织的形成和功能方面取得了一些进展，但我们仍然不完全了解离体环境下导致根和茎发育的分生组织形成。本研究计划的总体目标是提供体外分生组织和器官形成的机制理解。以拟南芥手杖期合子胚和根尖为外植体，设计了新的芽再生方案。我们的方案不同于传统的程序，在芽诱导培养基含有脱落酸（ABA）。这导致形成一个绿色的有机愈伤组织，从芽将持续发展。这种器官愈伤组织的精确鉴定使我们能够详细地研究茎的形成过程。此外，我们对拟南芥的使用使我们能够利用许多可用的转化系和定义的抗体来自信地研究发育过程的细节。本研究的目的是：(1)研究器官生愈伤组织的个体发生，并对负责新梢形成的器官生细胞进行表征；(2)研究与新梢形成相关的结构和分子事件；(3)研究新梢器官发生过程中激素分布和水平的变化；(4)研究ABA在再生过程中的作用模式。正如伊恩·苏塞克斯教授在他的评论（细胞56,225,1989）中所说：“分生组织构成植物”。如果没有功能性分生组织的形成，人们就不能声称在任何系统中取得了任何生物技术的成功。所获得的结果将为顶端分生组织的形成提供良好的理论理解和改进生物技术方案的设计。

The ability of plant cells and tissues to de-differentiate and give rise to shoots and roots under appropriate conditions forms the basis of modern day plant biotechnology. The key event in the generation of new functional shoots and roots is the formation of apical meristems. Apical meristems are responsible for tissue and organ formation of the primary plant body - the mother of all cells in plants. Although recent advances have been made in understanding apical meristem formation and function during normal plant development, we still do not fully understand meristem formation leading to root and shoot development from an in vitro environment. The overall goal of this research program is to provide a mechanistic understanding of in vitro meristem and organ formation. We have devised new protocols for shoot regeneration by using Arabidopsis zygotic embryos at the walking-stick stage and root tips as explants. Our protocol differs from the conventional procedure in that the shoot induction medium contains abscisic acid (ABA). This results in the formation of a green organogenic callus wherefrom shoots will consistently develop. This precise identification of the organogenic callus allows us to study the process of shoot formation in detail. Moreover, our use of Arabidopsis allows us to take advantage of the many available transformed lines and defined antibodies to study details of the developmental processes with confidence. The objectives of the proposed research are (1) to study the ontogeny of the organogenic callus and to characterize the organogenic cells that are responsible for shoot formation, (2) to study the structural and molecular events associated with shoot formation, (3) to study changes in the distribution and levels of hormones during the course of shoot organogenesis, and (4) to study the mode of action of ABA in the regeneration process. As Professor Ian Sussex stated in his review (Cell 56: 225, 1989) "The meristems make the plant". Without the formation of functional meristems, one cannot claim to have any biotechnological success in any system. The results obtained will provide a sound theoretical understanding of apical meristem formation and improved designs of protocols for biotechnology.