Studies on the regulatory mechanisms of growth of cultured plant cells and organelles

我们的研究目的是利用培养的植物细胞了解细胞生长、分化和细胞器发育的调控机制。我们在细胞和细胞器水平上分析了烟草细胞生长过程中的核酸和蛋白质合成、光合作用和呼吸活动。此外，我们还分析了烟草中一种被认为在细胞生长和分化过程中介导生长素作用的膜结合蛋白。结果表明：1)烟草2,4- d持续光营养系在光照条件下的光合活性。光合活性的发展与包括Rubisco在内的几种叶绿体蛋白的合成以及光系统II活性的发展有关；2)异养烟草细胞在细胞和线粒体水平上均表现出与生长周期相关的呼吸活性变化。呼吸活性的变化主要通过细胞色素途径发生，而抗氰替代途径的活性在整个生长周期内保持不变。外源糖供应的种类和数量不影响替代途径的相对贡献。我们的研究结果表明，呼吸受到腺苷酸的强烈控制，并表明替代途径起着能量溢出以外的作用；3)从烟草细胞悬浮培养物中溶出一种膜结合生长素结合蛋白（MABP），并对其进行了表征。结果表明，MABP是一类生长素结合蛋白，不同于细胞质可溶性蛋白。利用抗生长素变异和根癌农杆菌的转化，MABP被证明受细胞分裂素调节，并参与生长素介导的根分化。MABP在根分化中的作用也通过器官（根）培养系统得到证实，该系统可以控制根分化。少

Our research objectives were to understand the regulatory mechanisms of cell growth, differentiation and organellar development using cultured plant cells. We analyzed nucleic acid and protein syntheses, photosynthesis and respiratory activity during growth of tobacco cells at both the cellular and organellar levels. In addition, we analyzed a membrane-bound auxin-binding protein in tobacco which was thought to mediate auxin action in cell growth and differentiation.The results obtained are summarized as follows, i) photosynthetic activity developed in a 2,4-D-sustained photomixotrophic line of tobacco during growth in the light. The development of photosynthetic activity correlated with the synthesis of several chloroplast proteins including a small subunit of Rubisco and with the developwent of photosystem II activity; 2) heterotrophically grown tobacco cells showed growth cycle-related changes in the respiratory activity measured both at the cellular and mitochondrial levels. The ch … More anges in the respiratory activity occurred mainly through the cytochrome pathway, while the activity of the cyanide-resistant alternative pathway remained constant throughout the growth cycle. Kinds and amounts of sugars exogenously supplied did not affect the relative contribution of the alternative pathway. Our results show that the respiration is under strong control by adenylates and suggest that the alternative pathway plays a role other than an energy overflow; 3) a membrane-bound auxin-binding protein (MABP) was solubilized from cell suspension cultures of tobacco and characterized. The results show that MABP is a class of auxin-binding protein distinct from a cytosolic soluble type. Using an auxin-resistant variant and a transformant by agrobacterium tumefaciens, MABP was shown to be regulated by cytokinin and involved in auxin-mediated root differentiation. A role of MABP in root differentiation was also shown using an organ (root) culture system in which root differentiation could be manipulated. Less