In response to drought, miR169 is
down regulated, whereas its target NFYA5 is induced in
Arabidopsis [21]. Indeed, functional analyses have confirmed
that NFYA5-over expressing transgenic lines are
drought-tolerant, whereas miR169-over expressing plants
are drought-sensitive [21]. These findings demonstrate
that miR169-mediated NFYA5 regulation is crucial for
adaptation to drought stress. In contrast to the down regulation
of miR169 in Arabidopsis [21] and Medicago
truncatula [22], drought stress up regulated the expression
of miR169 g in rice (Oryza sativa) [23]. These conflicting
results highlight the need for more in-depth and detailed
characterizations of stress-responsive miRNAs in plants.