Abstract. Monoclonal antibodies specific for the muscle protein titin have been used in conjunction with muscle-specific antibodies against myofibrillar myosin heavy chains (MHCs) and desmin to study myogenesis in cultured cells. Desmin synthesis is initiated in replicating presumptive myoblasts, whereas the synthesis of titin and MHC is initiated simultaneously in their progeny, the postmitotic, mononucleated myoblasts. Both titin and MHC are briefly localized to nonstriated and thereafter to definitively striated myofibrils. At no stage during myofibrillogenesis is either protein observed as part of a sequence of mini-sarcomeres. Titin antibodies bind to the A-I junction, MHC antibodies to the A bands in nascent, maturing, and mature myofibrils. In contrast, desmin remains distributed as longitudinal filaments until well after the definitive myofibrils have aligned laterally. This tight temporal and topographical linkage between titin and myosin is also observed in postmitotic, mononucleated myoblasts and multinucleated myotubes when myoflbrillogenesis is perturbed with Colcemid or taxol. Colcemid induces elongating postmitotic mononucleated myoblasts and multinucleated myotubes to round up and form Colcemid myosacs. The myofibrils that emerge in these rounded cells are deployed in convoluted circles. The time required for their nonstriated myofibrils to transform into striated myofibrils is greatly protracted. Furthermore, as Colcemid induces immense desmin intermediate filament cables, the normal spatial relationships between emerging individual myofibrils is distorted. Despite these disturbances at all stages, the characteristic temporal and spatial relationship observed in normal myofibrils between titin and MHC is observed in myofibrils assembling in Colcemid-treated cells. Newly born postmitotic mononucleated myoblasts, or maturing myotubes, reared in taxol acquire a star-shaped configuration and are induced to assemble "pseudo-striated myofibrils" Pseudo-striated myofibrils consist of laterally aggregated 1.6-1xm long, thick filaments that interdigitate, not with thin filaments, but with long microtubules. These atypical myofibrils lack Z bands. Despite the absence of thin filaments and Z bands, titin localizes with its characteristic sarcomeric periodicity in pseudo-striated myofibrils. We conclude that the initiation and subsequent regulation of titin and myosin synthesis, and their spatial deployment within developing sarcomeres are tightly coupled events. These findings are discussed in terms of a model that proposes interaction between two relatively autonomous "organizing centers" in the assembly of each sarcomere.

Abstract. The phorbol ester TPA induces the sequential disassembly of myofibrils. First the alpha-actin thin filaments are disrupted and then, hours later, the myosin heavy chain (MHC) thick filaments. TPA does not induce the disassembly of the beta-and gammaactin thin filaments of stress fibers in presumptive myoblasts or fibroblasts, nor does it block the reemergence of stress fibers in 72-h myosacs that have been depleted of all myofibrillar molecules.There are differences in where, when, and how myofibrillar alpha-actin and MHC are degraded and eliminated from TPA-myosacs. Though the anisodiametric myotubes have begun to retract into isodiametric myosacs after 5 h in TPA, staining with anti-MHC reveals normal tandem A bands. In contrast, staining with mAb to muscle actin fails to reveal tandem I bands. Instead, both mAb to muscle actin and rhophalloidin brilliantly stain numerous disk-like bodies "-,3.0 I~m in diameter. These muscle actin bodies do not fuse with one another, nor do they costain with anti-MHC. All muscle actin bodies and/or molecules disappear in 36-h myosacs. The collapse of A bands is first initiated in 10-h myosacs. Their loss correlates with the appearance of immense, amorphous MHC patches. MHC patches range from a few micrometers to over 60 pm in size. They do not costain with antimuscle actin or rho-phalloidin. While diminishing in number and fluorescence intensity, MHC aggregates are present in 30% of the 72-h myosacs. Myosacs removed from TPA rapidly elongate, and after 48 h display normal newly assembled myofibrils. TPA reversibly blocks incorporation of [35S]methionine into myofibrillar alpha-actin, MHC, myosin light chains 1 and 2, the tropomyosins, and troponin C. It does not block the synthesis of beta-or gamma-actins, the nonmyofibrillar MHC or light chains, tubulin, vimentin, desmin, or most household molecules. 12-O-TETRADECANOYL phorbol-13-acetate (TPA) binds to protein kinase C, resulting in full activation at physiological concentrations of Ca 2+. Protein kinase C is present in many types of cells. It has a broad substrate specificity, phosphorylating seryl and threonyl residues in many proteins. TPA influences many major metabolic pathways directly by mobilizing protein kinase C and indirectly by altering the levels of inositol (1,4,5)-triphosphate and the activity of both the K + channels and the Na+/ H § exchanger (see references in 3,7,35,45,48).That the pleiotropic effects of TPA depend on the ongoing differentiation program of the responding cell is illustrated by its selective, but reversible, effects on cells in different compartments of the myogenic lineage. TPA acts as a mitogen for replicating presumptive myoblasts, inducing them to form long processes and form multilayers of ~fibroblastic" cells. These cells have the properties expected of cells arrested in the penultimate compartment of the myogenic lineage (25,31,64). Within minutes TPA also blocks the fusion of postmitotic mononucleated myoblasts into multinucleated myotubes (6,8,29,30). TPA has still other e...

Olive (Olea europaea L.) is one of the most economically important crop from east to the west around the world. The aim of this research was to investigate the genetic relationship among 41 olive genotypes, including 11 well-known Turkish cultivars and 30 Azerbaijani olive genotypes using simple sequence repeat (SSR) markers. In this study, 19 SSR markers were amplified 115 polymorphic SSR alleles. The number of polymorphic alleles ranged from 3 to 10 with an average of 6.05. The observed heterozygosity (Ho) varied from 0.05 to 0.93 with an average of 0.63 and expected heterozygosity (He) differed from 0.26 to 0.86 with an average of 0.72. The polymorphism information content (PIC) ranged from 0.23 to 0.85 with a mean of 0.68. A UPGMA cluster analysis grouped olive genotypes into two distinct clusters and both clusters were divided into two subgroups. Similarly, STRU CTU RE analysis assigned olive genotypes into two different gene pools (K = 2) and four gene pools were identified representing the two subgroups by STRU CTU RE analysis for K = 4. The genetic similarity of olive genotypes ranged from 0.36 to 0.95. These results revealed that there was a high genetic variation among 30 Azerbaijani olive genotypes. 'Ayvalık 1'and 'Ayvalık 2' from Azerbaijani olive genotypes were different from Turkish local olive cultivar, "Ayvalık" indicating homonymy. This research also highlighted that Azerbaijani olive genotypes were totally distinct from Turkish olive cultivars demonstrating that these olive genotypes might have been imported to Azerbaijan from different countries other than Turkey. The outcomes of this study indicated that these diverse olive genotypes could be useful for development of new olive varieties in Azerbaijan and future breeding programs between two countries could be enhanced by means of these results.