Figure 6. Identification of a plasma membrane-localized Al-transporter, HmPALT1, in hydrangea sepals.

(A) Al tolerance assay of HmPALT1. Δhsp150 and wild-type (WT) yeast cells carrying HmPALT1 or the empty vector (pYES2) were spotted onto LPP–uracil medium (pH 3.5) with or without 1 and 2 mM Al₂(SO₄)₃, and the plates were incubated at 30°C for 4 d. (B) The intracellular Al content of yeast cells that were transformed with HmPALT1. Yeast cells carrying HmPALT1 or the empty vector were exposed to different concentrations of Al₂(SO₄)₃ at pH 3.5 for 2 d. The intracellular Al content in both transformants increased with the Al in the medium in a dose-dependent manner. It is noteworthy, however, that the Al content of the yeast carrying HmPALT1 was approximately twice as much as that of the vector control cells, which was significant (**P<0.01 and *P<0.05 by Student's t test, respectively). The error bars represent SE (n = 3). (C) Subcellular localization of HmPALT1. The construct pHmPALT1-mCherry was simultaneously introduced into Welsh onion epidermal cells by particle bombardment with pPIP1A-GFP as a plasma membrane marker. The fluorescent signals were observed under microscopy 21 h after the bombardment. The merged image shows that HmPALT1 localizes to the plasma membrane. Scale bar = 50 µm.