Modulation of Arabidopsis CYCB1 expression patterns by polyamines and salt stress

Polyamines are new plant growth regulators that participate in various physiological processes modulating cell division and differentiation, stimulating secondary metabolite production and in stress responsiveness. In the present study, we evaluated the effect of polyamine application on CYCB1-GUS reporter line in Arabidopsis, in order to monitor changes in cell division. We observed that polyamines modulate the expression of CYCB1-GUS, most likely in an amine-specific manner. In particular, spermidine and spermine induced significant increases in CYCB1-GUS expression in shoot apex and root meristems. According of this view, mainly the higher polyamines stimulate the lateral root formation in Arabidopsis. Furthermore, the application of d-arginine and methylglyoxal bis-(guanylhydrazone) polyamine inhibitors drastically reduced Arabidopsis CYCB1-GUS root growth and plant fresh weight, as well as CYCB1-GUS expression. Another key point on this study was to analyze the effect of polyamines on CYCB1-GUS expression under salt stress. Salt stress treatments repressed CYCB1-GUS expression in a concentration dependent manner; this negative effect was ameliorated by polyamine application, in particular by spermidine and spermine, even at 125 mM NaCl, allowing the maintenance of CYCB1-GUS levels under salt stress. This work is one more contribution on the role of polyamines in cell cycle modulation and abiotic stress protection.