Tapetum Types and Forms in Angiosperms

Based on the analysis of literature and our own data, we have suggested a new version of the typification of types and forms of the tapetum. It is proposed to distinguish two types of tapetum: parietal and periplasmodial. Parietal tapetum lines the locule of microsporangium and this position is maintained throughout the development. A periplasmodial tapetum is characterised by the formation of a coenocyte as a result of the fusion of protoplasts, while the cytoplasm and nucleus are located not only between the developing microspores and pollen grains, but also come into contact with the inner layers of the cavity. The differences between tapetum types relate to the peculiarities of structural and temporal reorganisation in anther development. The protoplasts that form after the disappearance of the cell walls (usually at the stage of microspore tetrad, or after their disaggregation), gradually break down (form 1 – typical parietal tapetum), or they form protrusions inside the microsporangium cavity (form 2 – amoeboid tapetum). The protoplasts in the periplasmodial tapetum are formed before or during meiosis. They fuse resulting in a symplast. It is possible to distinguish two forms of periplasmodial tapetum: combining and invasing of protoplasts into the locule of microsporangium (form 1 – typical periplasmodial tapetum), and almost or partly fusion of protoplasts, which do not organise the invasions and maintain the initial position (form 2 – bordering symplast). Data on the diversity and structure of the tapetum, like any other characters, are used to clarify the position of taxa on the phylogenetic tree.

Microalgae protoplasts isolation and fusion for biotechnology research

Protoplasts are microbial or vegetable cells lacking a cell wall. These can be obtained from microalgae by an enzymatic hydrolysis process in the presence of an osmotic stabilizer. In general, protoplasts are experimentally useful in physiological, geneticand bio-chemical studies, so their acquisition and fusion will continue to be an active research area in modern biotechnology. The fusion of protoplasts in microalgae constitutes a tool for strain improvement because it allows both intra and interspecific genetic recombina-tion, resulting in organisms with new or improved characteristics of industrial interest. In this review we briefly describe themethod-ology for obtaining protoplasts, as well as fusion methods and the main applications of microalgal platforms.

Two tomato endoglucanases have a function during syncytium development

<em>Globodera rostochiensis</em>, as well as other cyst nematodes, induces formation of a multinucleate feeding site, called syncytium, in host roots. In tomato roots infected with a potato cyst nematode, the syncytium is initiated in the cortex or pericycle. Progressive cell wall dissolution and subsequent fusion of protoplasts of newly incorporated cells lead to syncytium formation. Expansion and development of a syncytium strongly depends on modifications of a cell wall, including its degradation, elongation, thickening, and formation of ingrowths within it in close contact with tracheary elements. Recent reports have demonstrated that during formation of syncytium, numerous genes of plant origin, coding for cell wall-modifying enzymes are up-re-gulated. In this research, we studied a detailed distribution and function of two tomato 1,4-β-endoglucanases in developing feeding sites induced by <em>G. rostochiensis</em>. In situ localization of tomato LeCel7 and LeCel8 transcripts and proteins demonstrated that these enzymes were specifically up-regulated within syncytium and in the cells adjacent to the syncytium. In non-infected roots an expression of LeCel7 and LeCel8 was observed in the root cap and lateral root primordia. Our data confirm that cell wall-modifying enzymes of plant origin have a role in a modification of cell wall within syncytia, and demonstrate that plant endoglucanases are involved in syncytia formation.

Fusion of protoplasts with irradiated microprotoplasts as a tool for radiation hybrid panel in citrus

The objective of this work was to combine asymmetric somatic hybridization (donor-recipient fusion or gamma fusion) to microprotoplast-mediated chromosome transfer, as a tool to be used for chromosome mapping in Citrus. Swinglea glutinosa microprotoplasts were irradiated either with 50, 70, 100 or 200 gamma rays and fused to cv. Ruby Red grapefruit or Murcott tangor protoplasts. Cell colonies were successfully formed and AFLP analyses confirmed presence of S. glutinosa in both 'Murcott' tangor and 'Ruby Red' grapefruit genomes.