Arabidopsis mutant plants with diverse defects in polyamine metabolism show unequal sensitivity to exogenous cadaverine probably based on their spermine content
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Arabidopsis plants do not synthesize the polyamine cadaverine, a five carbon-chain diamine and structural analog of putrescine. Mutants defective in polyamine metabolic genes were exposed to exogenous cadaverine. Spermine-deficient spms mutant grew well while a T-DNA insertion mutant (pao4-1) of polyamine oxidase (PAO) 4 was severely inhibited in root growth compared to wild type (WT) or other pao loss-of-function mutants. To understand the molecular basis of this phenomenon, polyamine contents of WT, spms and pao4-1 plants treated with cadaverine were analyzed. Putrescine contents increased in all the three plants, and spermidine contents decreased in WT and pao4-1 but not in spms. Spermine contents increased in WT and pao4-1. As there were good correlations between putrescine (or spermine) contents and the degree of root growth inhibition, effects of exogenously added putrescine and spermine were examined. Spermine mimicked the original phenomenon, whereas high levels of putrescine evenly inhibited root growth, suggesting that cadaverine-induced spermine accumulation may explain the phenomenon. We also tested growth response of cadaverine-treated WT and pao4-1 plants to NaCl and found that spermine-accumulated pao4-1 plant was not NaCl tolerant. Based on the results, the effect of cadaverine on Arabidopsis growth and the role of PAO during NaCl stress are discussed.
KeywordsArabidopsis Cadaverine NaCl response Polyamine oxidase Putrescine Spermidine Spermine
We thank to Prof. Taku Takahashi for providing us seeds of spms and acl5 mutants. This work was supported in part by Grant-in-Aids from the Japan Society for the Promotion of Science (JSPS) to TK (21380063), by the research funding programme “LOEWE -Landes-Offensive zur Entwicklung Wissenschaftlich-ökonomischer Exzellenz” of Hesse’s Ministry of Higher Education, Research, and the Arts to TB, and by the grants from The Saito Gratitude Foundation to GHMS (2011) and to DWK (2012) and by Sasagawa Scientific Research Grant to DWK. TL is financially supported by China Scholarship Council. GHMS is a recipient of MEXT fellowship.
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