EXPRESSION OF MIRS AND GENE TARGETS IN CEREAL GRAINS

MARGARIT, E., BERDAT, C., REGGIARDO, M., VALLEJOS, R.H

Mar del Plata, Bs.As., Argentina

Congreso; SAIB; 2007

SAIB

Our previous work has shown the expression of several conserved miRs in maize and wheat immature grains among other tissues. The level of some of these miRs changes abruptly during grain development. Thus miR167 expression increased more than 10 times in maize going from 7 to 14 DAP while miR159 and miR396 behaved otherwise dropping 10 and 3 times, respectively. Otherwise, in wheat, we observed a slight increase in miR156 and miR167 both in embryo and endosperm going from 7 to 14 DAP, in contrast to miR159, which showed an increase in embryo but maintained its expression levels in endosperm going from 7 to 14 DAP. We determined by 5´ RACE that the targets of miR167 were, in maize, ARF6 and ARF8 while processing of ARF8 was also observed in wheat, although ARF6 was not assayed. Measuring the level of these targets by Real-Time PCR we found that ARF6 and ARF8 expression decreased in immature maize grains from 7 to 14 DAP while the expression of miR167 increased during the same period of time. This inverse correlation was also observed in wheat embryos and endosperms from 7 to 14 DAP. Recently Yang et al. (NAR (2006) 34:1892-1899) showed that, in rice, miR167 levels respond to auxin concentration, down regulating ARF8. Thus in developing grains of maize and wheat the auxin signal may involve modification of miR167, ARF6 and ARF8 levels.