植物的发育:从细胞到个体

Plant development: From cells to individuals

随着分子生物学研究手段的丰富,植物发育生物学也从宏观的植物形态观察走向了微观的细胞和基因水平的研究.植物本身有着显著不同于动物的胚后发育特征,这种发育模式赋予了植物极其灵活的发育可塑性以应对不同的生长环境.在长期进化过程中,植物正是通过持续的调整发育来适应外界环境变化,造就了植物界丰富的多样性.本文以植物干细胞的功能和调控为核心,阐述了干细胞调控植物胚后发育的模式以及植物内源激素对干细胞和植物发育调控的贡献,讨论了内源的遗传信息和外部的环境因素在植物发育过程中的整合,以及这些因素如何调控农作物的器官和形态发育,继而影响到作物的产量.

As the development of research tools in molecular biology, plant developmental biology has been changed its focus from the descriptive analysis of plant morphology to the cellular and gene regulation level. Plants have distinct postembryonic development patterns compare to the animal, which give the plant a flexible developmental plasticity in response to different growth environments. In the long-term of evolution, plants are adapted to the environment changes through the continuous adjustment of their development strategy, which makes the plant world highly diverse. The growth and development of multicellular organisms depend on the maintenance and constant differentiation of stem cells. In plants, most of the organs originate from stem cells where resided in the shoot apical meristem, root apical meristem and cambium. The functional conservation of stem cells in those diverse plants is the basis for ontogenesis. However, from the perspective of evolutionary development, the diversity of key regulatory genes expression in different stem cell populations fulfills the continuous adjustments of development strategy to adapt to environmental changes. The plasticity in stem cell regulations determines the flexibility of plant development, which is conserved in plant kingdom from moss to angiosperms. Of course, the mechanism of stem cell maintenance and differentiation are even more complicated in angiosperms. In model plant of Arabidopsis thanian, the molecular mechanism of stem cell regulations has been extensively studied over the past decades. Multiple signaling molecules and transcription factors are found to tightly control the stem cell fate in Arabidopsis thaliana. The homeodomain transcription factor WUSCHEL（WUS） where expressed in the organizing center（OC） is a key regulator for plant stem cell fate determination. While, stem cells expressed secreted peptide CLV3, negatively regulates the expression of WUS. They form a negative feedback loop that tightly control plant stem cell fate. In addition, the classic phytohormones cytokinin and auxin also play essential roles in the maintenance of stem cells in shoot apical meristem, root apical meristem and cambium, and exhibit complex functional interactions. The molecular organization of the RAM is quite similar to that of the shoot. WOX5（WUSCHELRELATED HOMEOBOX 5）, a homologue of WUS, is expressed in the QC, and induces root stem cell fate in the surrounding cells. The GRAS family transcription factor SHORT-ROOT（SHR） is expressed in the innermost tissue of the root, and SHR moves to the surrounding cell layer activating SCARECROW（SCR）, together with PLT1 and PLT2, defines the stem cells fate. In this review, we focused on the functions of plant stem cells in plant postembryonic development, and covered recent findings on plant hormonal regulation in stem cells. We also discussed the integration of endogenous genetic information and external environmental factors in plant development, and how they affected the development of organs, morphology and yield of crops.