Abstract
Polyamines (PAs) like putrescine, spermidine, and spermine are ubiquitous polycationic molecules that occur in all living cells and have a role in a wide variety of biological processes. High amounts of spermidine conjugated to hydroxycinnamic acids are detected in the tryphine of Arabidopsis thaliana pollen grains. Tapetum localized spermidine hydroxycinnamic acid transferase (SHT) is essential for the biosynthesis of these anther specific tris-conjugated spermidine derivatives. Sht knockout lines show a strong reduction of hydroxycinnamic acid amides (HCAAs). The effect of HCAA-deficient anthers on the level of free PAs was measured by a new sensitive and reproducible method using 9-fluorenylmethyl chloroformate (FMOC) and fluorescence detection by HPLC. PA concentrations can be accurately determined even when very limited amounts of plant material, as in the case of A. thaliana stamens, are available. Analysis of free PAs in wild type stamens compared to sht deficient mutants and transcript levels of key PA biosynthetic genes revealed a highly controlled regulation of PA homeostasis in A. thaliana anthers.
Highlights
Polyamines (PAs) like spermidine, spermine, and their diamine precursor putrescine are small aliphatic molecules commonly found in prokaryotic and eukaryotic cells
Putrescine is synthesized in plants from either ornithine by ornithine decarboxylase (ODC) or from arginine by arginine decarboxylase (ADC)
Spermidine and spermine are synthesized from putrescine and decarboxylated SAM by spermidine synthase (SPDS) and spermine synthase (SPMS), respectively; dcSAM is produced from S-Adenosyl-l-methionine by SAM decarboxylase
Summary
Polyamines (PAs) like spermidine, spermine, and their diamine precursor putrescine are small aliphatic molecules commonly found in prokaryotic and eukaryotic cells. Due to their positive charges, PAs bind to macromolecules such as DNA, RNA, and proteins. A structural isomer of spermine, thermospermine, is required for stem elongation, since deficiency of thermospermine synthase (TSPMS) in A. thaliana resulted in dwarfism (Kakehi et al, 2008). Putrescine is synthesized in plants from either ornithine by ornithine decarboxylase (ODC) or from arginine by arginine decarboxylase (ADC). The positional isomer of spermine, thermospermine, is synthesized from spermidine by TSPMS (Fuell et al, 2010). PAs can be further metabolized into alkaloids (Biastoff et al, 2009) or be conjugated to hydroxycinnamic acids (Bassard et al, 2010)
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