The Fenestrin Antigen in Submembrane Skeleton of the Ciliate is Proposed as a Marker of Cell Polarity during Cell Division and in Oral Replacement

Tetrahymena thermophila cells have two types of polarized morphogenesis: divisional morphogenesis and oral reorganization (OR). The aim of this research is the analysis of cortical patterns of immunostaining during cell division and in OR using previously characterized antibodies against fenestrin and epiplasm B proteins. During cell division, the anarchic field of basal body proliferation of the new developing oral apparatus (AF) showed concomitant strong binding of the fenestrin antigen and withdrawal of a signal of the epiplasm B antigen. At a specific stage, the fenestrin antigen also appeared as a character of the anterior cortex pole, with a co-localized decrease in the detected epiplasm B antigen. The fenestrin antigen also showed a polarity of duplicating basal bodies in ciliary rows. Indirect immunofluorescence and immunogold labeling experiments were performed in the absence and presence of an inhibitor of activity of serine/threonine kinases, 6-dimethylaminopurine (6-DMAP) as an inducer of the oral replacement process. In the presence of 6-DMAP, one class of cells started OR, and some others were trapped and affected in cell division. Both types of cells showed an instability of oral structures and formed enlarged primordial oral fields. These anarchic fields (AFs) bind the fenestrin antigen, with disappearance of epiplasmic antigen staining. Only one protein (about 64 kDa) is detected in western blots by the anti-fenestrin antibody and it accumulated in 6-DMAP-treated cells that are involved in uncompleted morphogenetic activity. At a defined stage of oral development, both during cell division and in OR, the fenestrin antigen served as a marker of polarity of the cell of the anterior pole character.

Modifications of size and pattern of microtubular organelles in overfed cells of a ciliate Dileptus

The size of mouthparts and their constituent organelles was studied in cells of Dileptus anser, enlarged by overfeeding. The oral structures of large cells were either of normal dimensions and appearance, or they were enlarged and deformed in shape. The increase in size of mouthparts was accompanied by an increase in number of their microtubular organelles. There was, however, no net increase in size of the organelles, as defined by length and number of microtubules they contained. It is concluded that there exists an upward regulation in the size of the mouthparts as a whole, whilst the size of their constituent organelles is probably not so regulated. It is supposed that the patterning of normal-size organelles into large oral structure may lead to the observed deformations in the shape of the mouthparts.

Modifications of size and pattern of microtubular organelles in overfed cells of a ciliate Dileptus

The size of mouthparts and their constituent organelles was studied in cells of Dileptus anser, enlarged by overfeeding. The oral structures of large cells were either of normal dimensions and appearance, or they were enlarged and deformed in shape. The increase in size of mouthparts was accompanied by an increase in number of their microtubular organelles. There was, however, no net increase in size of the organelles, as defined by length and number of micro tubules they contained.

It is concluded that there exists an upward regulation in the size of the mouthparts as a whole, whilst the size of their constituent organelles is probably not so regulated. It is supposed that the patterning of normal-size organelles into large oral structure may lead to the observed deformations in the shape of the mouthparts.

Diminution of microtubular organelles after experimental reduction in cell size in the ciliate, Dileptus

Organelles of two kinds were studied: nemadesmata and transverse fibres, which are kinetosomal rootlets in oral parts of Dileptus. A diminution of microtubule number and length was found in organelles of size-reduced and regenerating cells, as compared to normal ones. It appeared, however, that organelles reduced in size were always larger and longer than could be expected on a basis of perfectly proportional regulation. The results give some insight into the modes of formation and regulation of the size of these organelles.

Regulation of ciliary pattern in dileptus (Ciliata). II. Formation of a cortical domain of sensory cilia from a domain of locomotor cilia

The surface of the ciliate Dileptus contains locomotor and sensory domains. Each domain contains cilia of its own kind, arranged in a characteristic pattern. Transformation of a portion of the locomotor area into the sensory domain has been studied. Locomotor ciliary units in the transforming area undergo resorption of ciliary shafts, which are subsequently replaced by shafts of a sensory type. Anterior to each transforming ciliary unit a new one is formed, and both acquire sensory rootlets. As a result, a double-kinetosomal sensory unit emerges. A regulatory change in structure occurs over a definite area that is determined to become the sensory cortical domain.

Regulation of ciliary pattern in Dileptus (Ciliata)

The surface of Dileptus contains three different regions: locomotor, oral and sensory.Each region has cilia with a specific structure and arranged in a characteristic pattern. In themorphogenetic situation when a sensory region transforms into a locomotor one, sensorycilia undergo structural changes converting them into locomotor cilia. The evidence for thisis that cilia are found in the transforming region with an inner microtubular pattern inter-mediate between that of sensory and locomotor cilia. There are also changes in distributionof sensory units leading to a pattern characteristic of locomotor cilia. The conversion ofsensory cilia into locomotor ones is also confirmed by a complete lack of evidence forresorption of sensory units within the transforming region, although the resorption is usuallyvery easily observed with the transmission electron microscope. Transformation lasts about5 h after the operation; afterwards locomotor cilia of normal appearance occupy the trans-formed region.

This way of regulation of ciliary pattern has not been previously described. Its mostsurprising feature is the regulation of inner structure in an already differentiated ciliaryunit. Some aspects of mechanisms which could control this kind of pattern regulation, are discussed.

Regulation of ciliary pattern in Dileptus (Ciliata). I. Sensory cilia and their conversion into locomotor cilia

The surface of Dileptus contains three different regions: locomotor, oral and sensory. Each region has cilia with a specific structure and arranged in a characteristic pattern. In the morphogenetic situation when a sensory region transforms into a locomotor one, sensory cilia undergo structural changes converting them into locomotor cilia. The evidence for this is that cilia are found in the transforming region with an inner microtubular pattern intermediate between that of sensory and locomotor cilia. There are also changes in distribution of sensory units leading to a pattern characteristic of locomotor cilia. The conversion of sensory cilia into locomotor ones is also confirmed by a complete lack of evidence for resorption of sensory units within the transforming region, although the resorption is usually very easily observed with the transmission electron microscope. Transformation lasts about 5 h after the operation; afterwards locomotor cilia of normal appearance occupy the transformed region. This way of regulation of ciliary pattern has not been previously described. Its most surprising feature is the regulation of inner structure in an already differentiated ciliary unit. Some aspects of mechanisms which could control this kind of pattern regulation, are discussed.

Proportional regulation of body form and cortical organelle pattern in the ciliate Dileptus

Morphometric and ultrastructural studies of shape and pattern regulation were performed on Dileptus anser. In this ciliate 2 body regions can be distinguished: proboscis and trunk. When a large portion of the trunk is excised, shape regulation occurs and the proper proboscis/trunk ratio is restored through elongation of the remnant of the trunk and shortening of the proboscis. When there is nothing but proboscis left, the trunk is formed from the proximal portion of proboscis and again the right proportion is restored. Regulation of the ciliary pattern is based mainly on resorption of some ciliary elements. The resorption of somatic ciliature is especially intense within narrowing regions, where otherwise overcrowding of cilia would occur. The resorption of oral ciliature was found to occur within an area located at the apex of the proboscis. Oral structures when damaged by cutting may be repaired in situ. Changes in the microfibrillar system of the cell were found during regulation of shape of the posterior region of the cell, as well as during regulation of size of oral structures. Regulatory processes in Dileptus are compared to those known for other ciliates, and possible differences between the regulation of shape and the regulation of pattern are discussed.