Modifying transient β-glucuronidase expression in pine species using introns

The effect of introns on gene expression was evaluated. Several intron-promoter combinations were introduced by microparticle bombardment into two pine species, stone pine (Pinus pinea L.) and salgare (n) over tilde o pine (Pinus nigra Am. ssp. Salzmannii (Dunal) Franco). Gene expression was evaluated by measuring transient GUS expression. Two promoters (CaMV35S and double CaMV35S modified) and two introns (intron 1 from maize genes alcohol dehydrogenase-1 and Shrunken-1) were used in our study. In both pine species tested, the Shl-int1 increased transient GUS expression from 2 to 6-fold compared to the intron-less construction. On the contrary, the inclusion of the Adhl-int1 associated with the double CaMV35S modified resulted in a dramatic decrease in the expression in both pine species analyzed. Our results suggest that Shl-int1 may be useful for the acquisition of the required levels of genetic activity of new agronomic traits introduced into pines.