抄録
Cowpea [Vigna unguiculata (L.) Walp.] is highly adapted to drought conditions and avoids water loss from
leaf by closing stomata via abscisic acid (ABA) signaling. Recently, molecular genetic studies in Arabidopsis
have revealed that the ABA responses are mediated by various long-distance signals and ABA transport
mechanisms. However, it remains unknown whether the transport mechanisms of ABA are involved in
significant drought tolerance of cowpea. Here we identified a set of ATP-binding cassette (ABC) transporter
gene candidates, VuABCG22, VuABCG25 and VuABCG40 by searching for ABA transporter homologs on
cowpea genome database. One VuABCG25, two VuABCG22 and four VuABCG40 were identified in cowpea
genome, while those corresponding homologs are single genes in Arabidopsis genome. Semi-quantitative RTPCR
analysis indicated that water stress including drought and salinity significantly induced up-regulation of
VuABCG25 expression but not VuABCG22 and VuABCG40. Three genes out of four VuABCG40 genes are
found in a gene cluster at the chromosome 1 in the cowpea genome. These results strongly suggest that ABArelated
ABC transporter genes are highly conserved between cowpea and Arabidopsis and that VuABCG25 is
involved in the ABA signaling pathway in cowpea under water stress.
