Figure 2: AtABCG31 and AtABCG25 are expressed mainly in the endosperm, whereas AtABCG30 and AtABCG40 are expressed specifically in the embryo.

(a–f) q-PCR analysis of AtABCG31 (a); AtABCG25 (b); AtEPR1, a gene specifically expressed in the endosperm (c); AtABCG40 (d); AtABCG30 (e); and AtABI4, a gene specifically expressed in the embryo (f). q-PCR was performed using total RNA extracted from dissected embryos or endosperms, or whole seeds of the Col-0 wild type. Data were normalized using AtUbiquitin11. E, dissected embryos; En, dissected endosperms; WS, whole seeds. Data are mean±s.e.m. of three independent experiments (N=3, n=2). (**P<0.01, ***P<0.005; (a,b,c) compared with the embryo (E) and (d,e,f) compared with the endosperm (En) by Student’s t-test). (g) AtABCG31 promoter–GUS (pAtABCG31::uidA) reporter gene activity was detected only in the endosperm, and not in the embryo (left). AtABCG30 promoter–GUS (pAtABCG30::uidA) and AtABCG40 promoter–GUS (pAtABCG40::uidA) activities were detectable only in the embryo and not in the endosperm (middle and right). Embryos (upper panel) and endosperms (lower panel) were dissected from mature seeds and incubated in GUS solution for 30 min. Results representative of 8 (AtABCG30), 12 (AtABCG31) and 9 (AtABCG40) different T3 promoter–GUS lines. Scale bar, 0.8 mm. (h) Plasma membrane localization of AtABCG31 and AtABCG30 in Arabidopsis mesophyll protoplasts. Protoplasts were isolated from Arabidopsis leaves transformed with p35S::sGFP::AtABCG31 (upper panels) or p35S::AtABCG30::GFP (lower panels) and pd35S::AtPIP2A::mCherry (PM-rK) using polyethylene glycol transformation. The left panel shows the GFP fluorescence of ABCGs, the middle panel the red mCherry fluorescence of the plasma membrane marker PM-rK protein and the right panel shows the merged images of GFP, mCherry and bright-field. Scale bar, 10 μm. GUS, β-glucuronidase.