Poster: Root biology

Abs # 698: Proteomic Studies on Aluminum-induced Membrane-bound Proteins in the Root Apices of Rye

Presenter:	Furukawa, Jun , junfurukawa@sa.uno.ne.jp
Authors	Furukawa, Jun  (A)   Ma, Jian Feng  (A)
Affiliations:	(A): Faculty of Agriculture, Kagawa University

Rye is a highly Al-resistant species. This species secretes both malate and citrate in response to Al from the root apex. Previous studies have suggested that a gene induction is required for the Al-induced secretion of citrate and that the secretion of citrate is mediated by an anion channel on the plasma membrane. However, neither the gene responsible for the citrate channel nor the channel protein itself has been isolated. In this study, Al-induced membrane-bound proteins was examined in rye to identify the Al-induced citrate channel. Three fractions of protein (soluble, intermediate soluble and insoluble) were extracted from the root apices (0-5 mm) exposed to 0, 20 (no root elongation inhibition) and 50 μM (35 % inhibition) of Al for 12 h and subjected to 2D-PAGE analysis. Totally, 31 proteins were induced by 20 μM Al, including seven in the soluble fraction, five in the intermediate soluble fraction, and 19 in the insoluble fraction. At 50 μM Al, additional six proteins in the soluble fraction, and two in the intermediate fraction were detected. Among the Al-induced intermediate soluble proteins, four proteins showed the up-regulated expression pattern with the increase of the Al concentration. However, proteins in the insoluble fraction were not affected by increasing Al concentration. Some candidate proteins in the intermediate soluble and insoluble fraction were subjected to LC-MS/MS analysis. Based on the peptide sequences determined, 16 proteins with partial homology were found in the databases. Among them, three genes including ATPase, 14-3-3 and VDAC (Voltage-dependent anion channel) were cloned from rye roots and then sequenced. The relationship between these gene expressions and the Al-induced citrate secretion is under investigation.