Ah. Warner et al., EFFECT OF ANAEROBIOSIS ON CYSTEINE PROTEASE REGULATION DURING THE EMBRYONIC-LARVAL TRANSITION IN ARTEMIA-FRANCISCANA, Journal of Experimental Biology, 200(5), 1997, pp. 897-908
Hydrated encysted embryos of the brine shrimp Artemia franciscana have
the ability to withstand years in anaerobic sea water using metabolic
strategies that enable them to inactivate all cell metabolic activiti
es and then to resume development when placed in aerobic sea water. Ho
wever, this unique characteristic of Artemia franciscana embryos is lo
st during a very short period, at the embryonic-larval transition peri
od of development, coincident with the appearance of prenauplius larva
e. Thus, while encysted embryos show complete inhibition of proteolysi
s over at least 4 years under anoxia, control of this activity, togeth
er with resistance to anoxia, is lost in newly hatched nauplius larvae
after only a few days in anaerobic sea water. In contrast to encysted
embryos, young larvae in anaerobic sea water produce large amounts of
lactic acid, which reaches a concentration of nearly 50 mmol l(-1) wi
thin 12 h of incubation. The accumulated lactic acid is believed to re
duce the intracellular pH (pHi) to considerably less than 6.3, the val
ue found in encysted embryos after 5 months in anaerobic sea water. We
find that larvae, in contrast to embryos, lose cytoplasmic proteins a
t the rate of 4-5 ngh(-1) larva(-1) upon transfer to anaerobic sea wat
er, while yolk proteins are not degraded in either embryos or larvae u
nder anoxic conditions. The decline in cytoplasmic protein levels in a
naerobic larvae may be due to activation of an endogenous cysteine pro
tease (CP) as the pHi becomes acidic. Contributing to the apparent unc
ontrolled CP activity is a decrease in the level of cysteine protease
inhibitor (CPI) activity during the embryonic-larval transition period
, resulting in an increase in the CP/CPI ratio, from approximately 0.5
in embryos to greater than 1.0 in newly hatched larvae. Finally, data
are presented to suggest that loss of the 26 kDa stress protein from
embryos during the embryonic-larval transition may also contribute to
the loss in resistance of young nauplius larvae of A. franciscana to a
naerobic conditions.