Spermine modulates the expression of two probable polyamine transporter genes and determines growth responses to cadaverine in Arabidopsis
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Two genes, LAT1 and OCT1 , are likely to be involved in polyamine transport in Arabidopsis. Endogenous spermine levels modulate their expression and determine the sensitivity to cadaverine.
Arabidopsis spermine (Spm) synthase (SPMS) gene-deficient mutant was previously shown to be rather resistant to the diamine cadaverine (Cad). Furthermore, a mutant deficient in polyamine oxidase 4 gene, accumulating about twofold more of Spm than wild type plants, showed increased sensitivity to Cad. It suggests that endogenous Spm content determines growth responses to Cad in Arabidopsis thaliana. Here, we showed that Arabidopsis seedlings pretreated with Spm absorbs more Cad and has shorter root growth, and that the transgenic Arabidopsis plants overexpressing the SPMS gene are hypersensitive to Cad, further supporting the above idea. The transgenic Arabidopsis overexpressing L-Amino acid Transporter 1 (LAT1) absorbed more Cad and showed increased Cad sensitivity, suggesting that LAT1 functions as a Cad importer. Recently, other research group reported that Organic Cation Transporter 1 (OCT1) is a causal gene which determines the Cad sensitivity of various Arabidopsis accessions. Furthermore, their results suggested that OCT1 is involved in Cad efflux. Thus we monitored the expression of OCT1 and LAT1 during the above experiments. Based on the results, we proposed a model in which the level of Spm content modulates the expression of OCT1 and LAT1, and determines Cad sensitivity of Arabidopsis.
KeywordsArabidopsis Cadaverine response L-Amino acid Transporter 1 Organic Cation Transporter 1 Polyamine Spermine
Drs. Miki Fujita and Kazuo Shinozaki (RIKEN, Japan) are acknowledged for providing the seeds of AtLAT1 overexpressed Arabidopsis lines and the rmv1 mutant. Dr. Matt Shenton is acknowledged for critically reading the manuscript. This work was supported by the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT) to TK (26·04081, 15K14705). GHMS is supported by the JSPS postdoctoral fellowship for foreign researchers.
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Conflict of interest
We declare that there is no conflict of interest in this manuscript.
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