In order to understand the microtubule change of monocotyls stem-tip during mitosis, the arrangement, transformation of microtubule array and its relation with chromosome movement during mitosis were studied with free...In order to understand the microtubule change of monocotyls stem-tip during mitosis, the arrangement, transformation of microtubule array and its relation with chromosome movement during mitosis were studied with freezing microtome, indirect immunofluoreseenee, DAPI staining and fluorescence microscopy. The results showed that nucleolus was intact when the cortical microtubules formed; cortical microtubules were changed into phramoplast microtubules bands at mitosis prophase. When phramoplast microtubules came into being, nuclear membrane was ruptured and chromosome was arranged at the position of cell plate ; subsequently, phramoplast microtubules were changed into phragmoplast microtubules, phramoplast microtubules were shortening and microtubules on the sides of cell plate were increasing gradually, during this course sister ehromatid was separated by microtubules at cell plate and tract to the two poles, forming phragmoplast microtubules. Then the nucleolus of two daughter cells formed and separated in the end with the increase of cells numbers. Therefore, cell division orientation could be judged from the arrangement of cell microtubules in different periods in order to understand its growth status.展开更多
The origin of cytoskeleton and the origin of relevant intracellular transportation system are big problems for understanding the emergence of eukaryotic cells. The present article summarized relevant information of ev...The origin of cytoskeleton and the origin of relevant intracellular transportation system are big problems for understanding the emergence of eukaryotic cells. The present article summarized relevant information of evidences and molecular traces on the origin of actin, tubulin, the chaperonin system for folding them, myosins, kinesins, axonemal dyneins and cytoplasmic dyneins. On this basis the authors proposed a series of works, which should be done in the future, and indicated the ways for reaching the targets. These targets are mainly: 1) the reconstruction of evolutionary path from MreB protein of archaeal ancestor of eukaryotic cells to typical actin; 2) the finding of the MreB or MreB-related proteins in crenarchaea and using them to examine J. A. Lake's hypothesis on the origin of eukaryote from "eocytes" (crenarchaea); 3) the examinations of the existence and distribution of cytoskeleton made of MreB-related protein within coccoid archaea, especially in amoeboid archaeon Thermoplasm acidophilum; 4) using Thermoplasma as a model of archaeal ancestor of eukaryotic cells; 5) the searching for the homolog of ancestral dynein in present-day living archaea. During the writing of this article, Margulis' famous spirochaete hypothesis on the origin of flagella and cilia was unexpectedly involved and analyzed from aspects of tubulins, dyneins and spirochaetes. Actually, spirochaete cannot be reasonably assumed as the ectosymbiotic ancestor of eukaryotic flagella and cilia, since their swing depends upon large amount of bacterial flagella beneath the flexible outer wall, but not depends upon their intracellular tubules and the assumed dyneins. In this case, if they had "evolved" into cilia and lost their bacterial flagella, they would immediately become immobile! In fact, tubulin and dynein-like proteins have not been found in any spirochaete.展开更多
基金Supported by the National Natural Science Foundation of China(30060038)~~
文摘In order to understand the microtubule change of monocotyls stem-tip during mitosis, the arrangement, transformation of microtubule array and its relation with chromosome movement during mitosis were studied with freezing microtome, indirect immunofluoreseenee, DAPI staining and fluorescence microscopy. The results showed that nucleolus was intact when the cortical microtubules formed; cortical microtubules were changed into phramoplast microtubules bands at mitosis prophase. When phramoplast microtubules came into being, nuclear membrane was ruptured and chromosome was arranged at the position of cell plate ; subsequently, phramoplast microtubules were changed into phragmoplast microtubules, phramoplast microtubules were shortening and microtubules on the sides of cell plate were increasing gradually, during this course sister ehromatid was separated by microtubules at cell plate and tract to the two poles, forming phragmoplast microtubules. Then the nucleolus of two daughter cells formed and separated in the end with the increase of cells numbers. Therefore, cell division orientation could be judged from the arrangement of cell microtubules in different periods in order to understand its growth status.
文摘The origin of cytoskeleton and the origin of relevant intracellular transportation system are big problems for understanding the emergence of eukaryotic cells. The present article summarized relevant information of evidences and molecular traces on the origin of actin, tubulin, the chaperonin system for folding them, myosins, kinesins, axonemal dyneins and cytoplasmic dyneins. On this basis the authors proposed a series of works, which should be done in the future, and indicated the ways for reaching the targets. These targets are mainly: 1) the reconstruction of evolutionary path from MreB protein of archaeal ancestor of eukaryotic cells to typical actin; 2) the finding of the MreB or MreB-related proteins in crenarchaea and using them to examine J. A. Lake's hypothesis on the origin of eukaryote from "eocytes" (crenarchaea); 3) the examinations of the existence and distribution of cytoskeleton made of MreB-related protein within coccoid archaea, especially in amoeboid archaeon Thermoplasm acidophilum; 4) using Thermoplasma as a model of archaeal ancestor of eukaryotic cells; 5) the searching for the homolog of ancestral dynein in present-day living archaea. During the writing of this article, Margulis' famous spirochaete hypothesis on the origin of flagella and cilia was unexpectedly involved and analyzed from aspects of tubulins, dyneins and spirochaetes. Actually, spirochaete cannot be reasonably assumed as the ectosymbiotic ancestor of eukaryotic flagella and cilia, since their swing depends upon large amount of bacterial flagella beneath the flexible outer wall, but not depends upon their intracellular tubules and the assumed dyneins. In this case, if they had "evolved" into cilia and lost their bacterial flagella, they would immediately become immobile! In fact, tubulin and dynein-like proteins have not been found in any spirochaete.
