Time- and dose-dependent gene expression in sea urchin embryos exposed to UVB

The increase of UVB radiation reaching ma rine environment has harm ful effec ts on living organism s. Parace ntrotus lividus sea urchin embr yos living in shal low water are expose d to radiations, providin g a good mod el for stud ying the molecu lar mec hanism s activated upon UV stress. Here, we report the modu lated time- and dose- depen dent expression of si x genes, known to be involved in stress response, in embr yos expose d at cleavage to 40 0 and 80 0 J/m 2 UVB, and collected at early (morula ) and later (gas trula) stages. We analyzed their mRNA levels by QPCR and found tha t Pl-14-3- 3 showed a dose- depen dent in duction , both ea rly and late in developmen t; Pl -c-jun was up- regulated proportionally to the UVB dos e at early stages and only at 80 0 J/m 2 UVB at later stages; Pl-XPB- ERCC3 , Pl -MT and Pl -NF-kB were hi ghly up-regulated later in development at the high dose, wi th the exception of Pl -XPB-E RCC3 who se mRNA levels were high also at the lower dose; Pl -FOXO exp ression was not affected by UVB ra- diation . We believe that the iden tifi cat ion of UVB -responsive genes in irradiated sea urchin embr yos, reported for the fi rst t ime in t his stud y, will be helpful for t he under standing of the involved mole cular pathways. The correlation be tween the impaired morph ogenesis, affecti ng endo- mesod erm differenti- ation, and gene mod ulations desc ribed herewith is also discussed .