EVIDENCE FOR INDEPENDENT RECRUITMENT OF ZETA-CRYSTALLIN QUINONE REDUCTASE (CRYZ) AS A CRYSTALLIN IN CAMELIDS AND HYSTRICOMORPH RODENTS/

Zeta-crystallin/quinone reductase (CRYZ) is an NADPH oxidoreductase ex pressed at very high levels in the lenses of two groups of mammals: ca melids and some hystricomorph rodents. It is also expressed at very lo w levels in all other species tested. Comparative analysis of the mech anisms mediating the high expression of this enzyme! crystallin in the lens of the Ilama (Lama guanacoe) and the guinea pig (Cavia porcellus ) provided evidence for independent recruitment of this enzyme as a le ns crystallin in both species and allowed us to elucidate for the firs t time the mechanism of lens recruitment of an enzyme-crystallin. The data presented here show that in both species such recruitment most li kely occurred through the generation of new lens promoters from nonfun ctional intron sequences by the accumulation of point mutations and/or small deletions and insertions. These results further support the ide a that recruitment of CRYZ resulted from an adaptive process in which the high expression of CRYZ in the lens provides some selective advant age rather than from a purely neutral evolutionary process.