Developmental arrest

Proplastids are small colorless or pale green undifferentated plastids that occur in the meristematic cells of roots and stems. Proplastids are precursors of more highly differentiated plastids. Etioplasts are proplastids containing prolemellar bodies and are precursors of chloroplasts developmentally arrested by low light levels. 

In the general spectrum of host-parasite relationships, there is considerable parasite-induced host variability resulting in perturbed host physiology, biochemistry, and developmental behavior (8, 21, 22). There is a wide range of speculation that the parasite has the capacity to modulate or regulate host systems (8, 10, 23). It is clear that the C. sonorensis polydnavirus induces developmental arrest in H. virescens larva (18, 24,... 

Miller, S. E. and Hadfield, M. G., Developmental arrest during larval life and life-span extension in a marine mollusc, Science, 248, 356, 1990. 

However, presence of SLC proteins beyond the pre-B cell stage severely hampered B cell development. At the immature B cell stage the SLC components had the capacity - in the presence of conventional Ig LC - to induce constitutive BCR internalization. The internalization was dependent on the adapter protein SLP65 (SH2 domain-containing leukocyte-specific phosphoprotein of 65 kDa, or BASH/BLNK) that is downstream of the (pre-)BCR. Internalization of the BCR at the immature B cell stage resulted in secondary Ig LC rearrangements, reflected by increased fractions of Ig L+ cells and a severe developmental arrest of immature B cells. 

Winska P, Golos B, Ciesla J, Zielinski Z, Frqczyk T, Walajtys-Rode E, Rode W (2005) Developmental arrest in C. elegans dauer larvae leaves high expression of enzymes involved in thymidylate biosynthesis, similar to that found in TrichineUa muscle larvae. Parasitology 131 247-254... 

Mueller, A. K., Camargo, N., Kaiser, K., Andorfer, C., Frevert, U., Matuschewski, K., and Kappe, S. H. (2005). Plasmodium liver stage developmental arrest by depletion of a protein at the parasite-host interface. Proc. Natl. Acad. Sci. USA 102,3022-3027. 

The third hypothesis suggested is that elevated adenosine levels lead to inappropriate activation of adenosine receptors. Adenosine is also a signaling molecule, and stimulation of the adenosine receptors results in activation of protein kinase A and elevated cAMP levels in thymocytes. Elevated levels of cAMP in these cells triggers both apoptosis and developmental arrest of the cell. 

Similarly, parasitism of P. separata, by A. kariyai or injection of the calyx fluid or virus material from the parasitoid, caused a decline in the host ecdysteroid titer and arrested metamorphosis of the host (54). Again, injection of exogenous 20-hydroxyecdysone reversed the developmental arrest. In this case, administration of prothoracicotropic hormone caused a reactivation of the prothoracic glands in the treated host. These results showed that the virus material inhibited the synthesis or secretion of prothoracicotropic hormone and also lowered the ecdysteroid level in the host. Also in this case, a mixture of both venom and calyx fluid were needed to obtain the full prolongation of the larval stage in the host (110). 

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